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# hspice_sa - HSPICE® User Guide: Simulation and Analysis...

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Unformatted text preview: HSPICE® User Guide: Simulation and Analysis Version B-2008.09, September 2008 Copyright Notice and Proprietary Information Copyright © 2008 Synopsys, Inc. All rights reserved. This software and documentation contain confidential and proprietary information that is the property of Synopsys, Inc. The software and documentation are furnished under a license agreement and may be used or copied only in accordance with the terms of the license agreement. No part of the software and documentation may be reproduced, transmitted, or translated, in any form or by any means, electronic, mechanical, manual, optical, or otherwise, without prior written permission of Synopsys, Inc., or as expressly provided by the license agreement. Right to Copy Documentation The license agreement with Synopsys permits licensee to make copies of the documentation for its internal use only. Each copy shall include all copyrights, trademarks, service marks, and proprietary rights notices, if any. Licensee must assign sequential numbers to all copies. These copies shall contain the following legend on the cover page: “This document is duplicated with the permission of Synopsys, Inc., for the exclusive use of __________________________________________ and its employees. This is copy number __________.” Destination Control Statement All technical data contained in this publication is subject to the export control laws of the United States of America. Disclosure to nationals of other countries contrary to United States law is prohibited. It is the reader’s responsibility to determine the applicable regulations and to comply with them. Disclaimer SYNOPSYS, INC., AND ITS LICENSORS MAKE NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARD TO THIS MATERIAL, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. Registered Trademarks (®) Synopsys, AMPS, Astro, Cadabra, CATS, Design Compiler, DesignWare, Formality, HSPICE, iN-Phase, Leda, MAST, ModelTools, NanoSim, OpenVera, PathMill, Physical Compiler, PrimeTime, SiVL, SNUG, SolvNet, TetraMAX, VCS, Vera, and YIELDirector are registered trademarks of Synopsys, Inc. Trademarks (™) AFGen, Apollo, Astro-Rail, Astro-Xtalk, Aurora, AvanWaves, Columbia, Columbia-CE, Cosmos, CosmosLE, CosmosScope, CRITIC, DC Expert, DC Professional, DC Ultra, Design Analyzer, DesignPower, Design Vision, DesignerHDL, Direct Silicon Access, Discovery, Eclypse, Encore, EPIC, Galaxy, HANEX, HDL Compiler, Hercules, Hierarchical Optimization Technology, HSIM, HSIMplus, in-Sync, iN-Tandem, i-Virtual Stepper, Jupiter, Jupiter-DP, JupiterXT, JupiterXT-ASIC, Liberty, Libra-Passport, Library Compiler, Magellan, Mars, Mars-Rail, Mars-Xtalk, Milkyway, ModelSource, Module Compiler, Planet, Planet-PL, Polaris, Power Compiler, Raphael, Saturn, Scirocco, Scirocco-i, StarRCXT, Star-SimXT, System Compiler, Taurus, TSUPREM-4, VCS Express, VCSi, VHDL Compiler, VirSim, and VMC are trademarks of Synopsys, Inc. Service Marks (sm) MAP-in, SVP Café, and TAP-in are service marks of Synopsys, Inc. SystemC is a trademark of the Open SystemC Initiative and is used under license. ARM and AMBA are registered trademarks of ARM Limited. Saber is a registered trademark of SabreMark Limited Partnership and is used under license. All other product or company names may be trademarks of their respective owners. ii HSPICE® User Guide: Simulation and Analysis B-2008.09 Contents Inside this Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The HSPICE Documentation Set. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxviii Customer Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. xxxvi Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Part I: xxxiii xxxix Introduction to HSPICE 3 HSPICE Varieties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 HSPICE Features for Running Higher-Level Simulations . . . . . . . . . . . . . . . . 7 Simulation Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Experimental Methods Supported by HSPICE . . . . . . . . . . . . . . . . . . . . 7 Simulation Process Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Setting Environment Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 License Variable. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Temporary Directory Variable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . License Queuing Variable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Windows Variable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 12 12 13 Standard Input Files. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Design and File Naming Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Output Configuration File (meta.cfg) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Initialization File (hspice.ini) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 DC Operating Point Initial Conditions File . . . . . . . . . . . . . . . . . . . . . . . . 15 Input Netlist File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Library Input File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Analog Transition Data File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Standard Output Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 iii Contents AC Analysis Results File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 AC Analysis Measurement Results File . . . . . . . . . . . . . . . . . . . . . . . . . . 17 DC Analysis Results File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 DC Analysis Measurement Results File. . . . . . . . . . . . . . . . . . . . . . . . . . 18 Digital Output File. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 FFT Analysis Graph Data File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Operating Point Information File. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Operating Point Node Voltages File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Output Listing File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Output Status File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Output Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Subcircuit Cross-Listing File. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Transient Analysis Measurement Results File . . . . . . . . . . . . . . . . . . . . . 21 Transient Analysis Results File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Waveform Viewing File. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Working Directory Path Character Limit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Startup and Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Running HSPICE Simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Running HSPICE Simulations on Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Running HSPICE RF Simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Running HSPICE Interactively . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Starting Interactive Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 18 Hardcopy Graph Data File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Running a Command File in Interactive Mode . . . . . . . . . . . . . . . . . . . . . 28 Running Multithreading or Multiprocessing HSPICE Simulations . . . . . . . . . . 28 To Run Multithreading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Performance Improvement Estimations . . . . . . . . . . . . . . . . . . . . . . 28 29 Multiprocessing .ALTER Cases, Transient Sweeps, Monte Carlo . . . . . . .ALTER Cases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Transient Sweeps and Monte Carlo Trials . . . . . . . . . . . . . . . . . . . . Multiprocessing Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 30 31 31 Using HSPICE in Client/Server Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 To Start Client/Server Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Server. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Client . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv 27 Quitting Interactive Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 32 32 Contents To Simulate a Netlist in Client/Server Mode. . . . . . . . . . . . . . . . . . . . . . . 33 To Quit Client/Server Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 34 Application Instances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Running HSPICE to Calculate New Measurements . . . . . . . . . . . . . . . . . . . . 38 To Calculate New Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. 33 Launching the Advanced Client/Server (C/S) Mode . . . . . . . . . . . . . . . . Command Syntax. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Input Netlist and Data Entry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Input Netlist File Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Input Line Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Special Characters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 First Character . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 Delimiters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 Instance Names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 Hierarchy Paths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 Numbers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 Parameters and Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 Input Netlist File Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 Schematic Netlists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 Input Netlist File Composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 HSPICE Topology Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 Title of Simulation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 Comments and Line Continuation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 Element and Source Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 Defining Subcircuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 Node Name (or Node Identifier) Conventions . . . . . . . . . . . . . . . . . . . . . Using Wildcards on Node Names . . . . . . . . . . . . . . . . . . . . . . . . . . 59 61 Element, Instance, and Subcircuit Naming Conventions . . . . . . . . . . . . . 63 Subcircuit Node Names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 Path Names of Subcircuit Nodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 Abbreviated Subcircuit Node Names . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 Automatic Node Name Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 Global Node Names. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 Circuit Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 Data-Driven Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 Library Calls and Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Library Building Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 67 v Contents Automatic Library Selection (HSPICE). . . . . . . . . . . . . . . . . . . . . . . . . . . 67 Defining Parameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Predefined Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Measurement Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Outputting Pass/Fail Measure Data . . . . . . . . . . . . . . . . . . . . . . . . . 68 68 68 68 Altering Design Variables and Subcircuits . . . . . . . . . . . . . . . . . . . . . . . Using Multiple .ALTER Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 69 Connecting Nodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 Deleting a Library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 Ending a Netlist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 Using Subcircuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 Hierarchical Parameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M (Multiply) Parameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S (Scale) Parameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using Hierarchical Parameters to Simplify Simulation . . . . . . . . . . . 74 74 75 76 Undefined Subcircuit Search (HSPICE). . . . . . . . . . . . . . . . . . . . . . . . . . 77 Troubleshooting Subcircuit Node Issues . . . . . . . . . . . . . . . . . . . . . . . . . 78 Subcircuit Call Statement Discrete Device Libraries . . . . . . . . . . . . . . . . . . . . 79 DDL Library Access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 Vendor Libraries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 Subcircuit Library Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 Post-Layout Back-Annotation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 Invoking Post-Layout Back-Annotation. . . . . . . . . . . . . . . . . . . . . . . . . . . DSPF and SPEF File Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 84 Using Interactive Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 Invoking Interactive Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 Quitting Interactive Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 Executing an Interactive Script. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 Getting Help . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5. 70 Condition-Controlled Netlists (IF-ELSE). . . . . . . . . . . . . . . . . . . . . . . . . . 88 Creating a Netlist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 Running an Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 Viewing a Netlist. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 Loading and Running an Existing Netlist . . . . . . . . . . . . . . . . . . . . . . . . . 89 Using Environment Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi 88 Specifying an Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 Contents Recording and Saving Interactive Commands to a File . . . . . . . . . . . . . . 91 Printing a Voltage Value During Simulation . . . . . . . . . . . . . . . . . . . . . . . 93 Running Multiple Testcases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 HSPICE GUI for Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 Working with Designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 Configuring the HSPICE GUI for Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . 6. 92 Using a Command File to Run HSPICE in Interactive Mode . . . . . . . . . . 97 Launching Waveview in HSPUI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 Running Multiple Simulations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 Building the Batch Job List. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 Simulating a Batch Job . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sample Batch Work-Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 102 Running Multi-Threading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 Metaencrypt and Converter Utilities, Client/Server Operation . . . . . . . . . . . . . 104 CMI Directory Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 Troubleshooting Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 Setting the hspui.cfg File Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 Text Editor Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 Simulating a UNIX Netlist File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7. 98 Setting up Windows for Verilog-A. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 Library and Data Encryption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 Library Encryption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 Encrypting a Model Library Using the metaencrypt Utility . . . . . . . . . . . . 108 Three Encryption Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 Installing and Running metaencrypt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 Installing metaencrypt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 Running metaencrypt. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 Encryption Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 General Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 Traditional Library Encryption. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 Creating Files Using Traditional Encryption . . . . . . . . . . . . . . . . . . . . . . . Non-Library Encrypted Portions . . . . . . . . . . . . . . . . . . . . . . . . . . . . *.lib File Encryption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 115 115 vii Contents Example: Traditional (freelib) Encryption in an HSPICE Netlist . . . . . . . . . . . . 116 8-Byte Key Encryption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 Creating 8-byte key Encryption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 Placing an 8-byte key Encrypted File into a HSPICE Netlist . . . . . . . . . . 119 Triple DES Public and Random Keys. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 Creating 3DES Encrypted Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 ‘Bad encryption format’ or ‘version check failed’ error . . . . . . . . . . . . . . . 123 **warning** parameters... as an expression containing output signals . . 8. 122 Troubleshooting Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Part II: 121 Placing 3DES Encryption Files into a HSPICE Netlist . . . . . . . . . . . . . . . 124 Elements and Devices 127 Passive Elements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 Values for Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 Resistor Elements in a HSPICE or HSPICE RF Netlist . . . . . . . . . . . . . . Linear Resistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Behavioral Resistors in HSPICE or HSPICE RF . . . . . . . . . . . . . . . Frequency-Dependent Resistors . . . . . . . . . . . . . . . . . . . . . . . . . . . Skin Effect Resistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 131 132 132 133 Capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Linear Capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Frequency-Dependent Capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . Behavioral Capacitors in HSPICE or HSPICE RF . . . . . . . . . . . . . . DC Block Capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Charge-Conserved Capacitors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 136 138 139 139 139 Inductors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mutual Inductors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ideal Transformer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Linear Inductors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Frequency-Dependent Inductors . . . . . . . . . . . . . . . . . . . . . . . . . . . AC Choke Inductors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reluctors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 144 146 148 149 150 150 Multi-Terminal Linear Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153 W-element (Distributed Transmission Lines) . . . . . . . . . . . . . . . . . . . . . . W-element Statement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154 154 U-element (Lumped Transmission Lines). . . . . . . . . . . . . . . . . . . . . . . . . viii Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 Contents S-element (Generic Multiport). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Group Delay Handler in Time Domain Analysis . . . . . . . . . . . . . . . . Preconditioning S-parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160 160 161 Active Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 Diode Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 Bipolar Junction Transistor (BJT) Element . . . . . . . . . . . . . . . . . . . . . . . . 167 MOSFETs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 Extended MOSFET Element Support Using .OPTION MACMOD . . . . . Direct X-Element Mapping to a MOSFET Model Card. . . . . . . . . . . 171 175 IBIS Buffers (HSPICE Only). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9. 164 JFETs and MESFETs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176 Sources and Stimuli . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 Independent Source Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 Source Element Conventions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180 Independent Source Element Syntax. . . . . . . . . . . . . . . . . . . . . . . . . . . . 180 DC Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 AC Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 Transient Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 Mixed Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 Port Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 Independent Source Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188 Trapezoidal Pulse Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188 Sinusoidal Source Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192 Exponential Source Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196 Piecewise Linear Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . General Form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MSINC and ASPEC Form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Data-Driven Piecewise Linear Source . . . . . . . . . . . . . . . . . . . . . . . 199 199 199 201 Single-Frequency FM Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202 Single-Frequency AM Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pattern Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204 207 Pseudo Random-Bit Generator Source . . . . . . . . . . . . . . . . . . . . . . . . . . Linear Feedback Shift Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conventions for Feedback Tap Specification . . . . . . . . . . . . . . . . . . 211 213 214 Voltage and Current Controlled Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 Polynomial Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . One-Dimensional Function. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 217 ix Contents Two-Dimensional Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Three-Dimensional Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . N-Dimensional Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Piecewise Linear Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221 Power Sources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221 Independent Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using the Keyword POWER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Power Calculation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Subcircuit Power Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222 222 224 224 Controlled Sources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 Voltage-Dependent Voltage Sources — E-elements . . . . . . . . . . . . . . . . . . . . 225 Voltage-Controlled Voltage Source (VCVS) . . . . . . . . . . . . . . . . . . . . . . . Linear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Polynomial (POLY) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Piecewise Linear (PWL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Multi-Input Gates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Delay Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Laplace Transform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pole-Zero Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Frequency Response Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Foster Pole-Residue Form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Behavioral Voltage Source (Noise Model) . . . . . . . . . . . . . . . . . . . . Ideal Op-Amp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ideal Transformer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E-element Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226 226 226 226 226 227 227 228 229 230 231 232 232 233 E-element Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ideal OpAmp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Voltage Summer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Polynomial Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Zero-Delay Inverter Gate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Delayed and Inverted Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Differential Amplifiers and Opamp Signals . . . . . . . . . . . . . . . . . . . Ideal Transformer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Voltage-Controlled Oscillator (VCO). . . . . . . . . . . . . . . . . . . . . . . . . 235 235 236 236 236 236 237 237 237 Using the E-element for AC Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 Current-Dependent Current Sources — F-elements . . . . . . . . . . . . . . . . . . . . 240 Current-Controlled Current Source (CCCS) Syntax. . . . . . . . . . . . . . . . . Linear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Polynomial (POLY) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Piecewise Linear (PWL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Multi-Input Gates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Delay Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x 218 219 220 240 240 241 241 241 241 Contents F-element Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-element Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 243 Voltage-Dependent Current Sources — G-elements. . . . . . . . . . . . . . . . . . . . 244 Voltage-Controlled Current Source (VCCS) . . . . . . . . . . . . . . . . . . . . . . . Linear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Polynomial (POLY) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Piecewise Linear (PWL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Multi-Input Gate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Delay Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Laplace Transform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pole-Zero Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Frequency Response Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Foster Pole-Residue Form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245 245 245 245 246 246 246 246 246 246 Behavioral Current Source (Noise Model) . . . . . . . . . . . . . . . . . . . . . . . . 246 Voltage-Controlled Resistor (VCR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Linear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Polynomial (POLY) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Piecewise Linear (PWL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Multi-Input Gates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 248 248 248 249 Voltage-Controlled Capacitor (VCCAP) . . . . . . . . . . . . . . . . . . . . . . . . . . NPWL Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PPWL Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G-element Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 249 250 250 G-element Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Modeling Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Switch-Level MOSFET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Runtime Current Source with Equation Containing Output Variable Voltage-Controlled Capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Zero-Delay Gate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Delay Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Diode Equation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Diode Breakdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Triodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Behavioral Noise Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253 253 254 254 255 255 255 255 256 256 256 Current-Dependent Voltage Sources — H-elements . . . . . . . . . . . . . . . . . . . . 256 Current-Controlled Voltage Source (CCVS) . . . . . . . . . . . . . . . . . . . . . . . Linear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Polynomial (POLY) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Piecewise Linear (PWL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Multi-Input Gate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Delay Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257 257 257 257 257 257 Specifying a Digital Vector File and Mixed Mode Stimuli . . . . . . . . . . . . . . . . . 261 xi Contents Commands in a Digital Vector File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261 Vector Patterns. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261 Defining Tabular Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Input Stimuli . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Expected Output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Verilog Value Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Periodic Tabular Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262 263 263 264 265 Waveform Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266 Modifying Waveform Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266 Using the Context-Based Control Option . . . . . . . . . . . . . . . . . . . . . . . . . 267 Comment Lines and Line Continuations . . . . . . . . . . . . . . . . . . . . . . . . . 268 Parameter Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . First Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Second Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Third Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268 269 269 270 Digital Vector File Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271 10. Parameters and Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273 Using Parameters in Simulation (.PARAM) . . . . . . . . . . . . . . . . . . . . . . . . . . . 273 Defining Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273 Assigning Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Example: Modeling an eFuse. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Inline Parameter Assignments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Parameters in Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275 276 276 276 User-Defined Function Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276 Predefined Analysis Function. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277 Measurement Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277 .PRINT and .PROBE Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278 Multiply Parameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278 Using Algebraic Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278 Built-In Functions and Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279 Parameter Scoping and Passing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283 Library Integrity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285 Creating Parameters in a Library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285 String Parameter (HSPICE Only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287 String Parameters in Passive and Active Component Keywords . . . . . . . 288 Parameter Defaults and Inheritance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Parameter Passing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xii 284 Reusing Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 291 Contents Parameter Passing Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292 11. Simulation Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293 Overview of Output Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294 Output Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294 Output Variables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295 Displaying Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296 .PRINT Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Statement Order. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296 296 .PROBE Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296 Using Wildcards in PRINT and PROBE Statements . . . . . . . . . . . . . . . . Supported Wildcard Templates (HSPICE only) . . . . . . . . . . . . . . . . 297 297 Print Control Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Changing the File Descriptor Limit (HSPICE Only) . . . . . . . . . . . . . 298 298 Printing the Subcircuit Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299 Selecting Simulation Output Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300 DC and Transient Output Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nodal Capacitance Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nodal Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Current: Independent Voltage Sources . . . . . . . . . . . . . . . . . . . . . . Current: Element Branches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Current: Subcircuit Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Power Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wildcard Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Print Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Diode Power Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BJT Power Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . JFET Power Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MOSFET Power Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301 301 302 302 302 306 306 306 307 307 308 309 309 AC Analysis Output Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nodal Capacitance Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nodal Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Current: Independent Voltage Sources . . . . . . . . . . . . . . . . . . . . . . Current: Element Branches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Current: Subcircuit Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Group Time Delay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Noise and Distortion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310 311 311 313 313 314 314 315 315 Element Template Output (HSPICE Only) . . . . . . . . . . . . . . . . . . . . . . . . 316 Specifying User-Defined Analysis (.MEASURE) . . . . . . . . . . . . . . . . . . . . . . . 317 xiii Contents .MEASURE Statement Order. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318 .MEASURE Parameter Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318 FIND and WHEN Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319 Equation Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320 Average, EM_AVG, RMS, MIN, MAX, INTEG, and PP . . . . . . . . . . . . . . Measuring Recovered Electromigration . . . . . . . . . . . . . . . . . . . . . . 320 321 INTEGRAL Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322 DERIVATIVE Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322 ERROR Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Error Equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322 322 Expected State of Digital Output Signal (.DOUT) . . . . . . . . . . . . . . . . . . . . . . 324 Reusing Simulation Output as Input Stimuli (HSPICE Only) . . . . . . . . . . . . . . 326 Reusing the PAR(...) output as input to other elements . . . . . . . . . . . . . . 326 Output Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328 Element Template Listings (HSPICE Only) . . . . . . . . . . . . . . . . . . . . . . . . . . . 329 Redirecting the Simulation Output Results Files to a Different Directory. . . . . 336 Using the HSPICE Output Converter Utility . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 Converter Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 PSF Converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 PWL/DATA/VEC Converter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Input Line Dependencies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338 341 Running the Converter Utility in Batch Mode . . . . . . . . . . . . . . . . . . . . . . 341 Troubleshooting Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342 Resolving Inductor/Voltage Source Loop Errors . . . . . . . . . . . . . . . . . . . 342 Voltage Source Missing Rising and Falling Edges . . . . . . . . . . . . . . . . . 343 Part III: Analyses 12. Initializing DC/Operating Point Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . Simulation Flow—Initialization and Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . 347 DC Initialization and Operating Point Calculation . . . . . . . . . . . . . . . . . . . . . . 350 .OP Statement — Operating Point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351 352 Element Statement IC Parameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352 Initial Conditions and UIC Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . 353 .SAVE and .LOAD Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiv 347 354 Contents .DC Statement—DC Sweeps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354 Other DC Analysis Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355 DC Initialization Control Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356 Accuracy and Convergence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356 Accuracy Tolerances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357 Accuracy Control Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359 Autoconverge Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . DCON and GMINDC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359 360 Reducing DC Errors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364 Shorted Element Nodes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365 Inserting Conductance, Using DCSTEP . . . . . . . . . . . . . . . . . . . . . . . . . 365 Floating-Point Overflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366 Diagnosing Convergence Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367 Non-Convergence Diagnostic Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367 Traceback of Non-Convergence Source . . . . . . . . . . . . . . . . . . . . . . . . . 369 Solutions for Non-Convergent Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . Poor Initial Conditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Inappropriate Model Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . PN Junctions (Diodes, MOSFETs, BJTs). . . . . . . . . . . . . . . . . . . . . Convergence Failure: Too Many Current Probes in Netlist. . . . . . . . 369 369 370 372 374 13. Pole/Zero Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375 Overview of Pole/Zero Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375 Using Pole/Zero Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376 Matrix Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376 Muller Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377 How HSPICE Calculates Poles and Zeros. . . . . . . . . . . . . . . . . . . . . . . . 377 Pole/Zero Analysis Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378 Example 1 – Low-Pass Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378 Example 2 – Kerwin’s Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 381 Example 3 – High-Pass Butterworth Filter . . . . . . . . . . . . . . . . . . . . . . . . 382 Example 4 – CMOS Differential Amplifier . . . . . . . . . . . . . . . . . . . . . . . . 383 Example 5 – Simple Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386 Example 6— Active Low-Pass Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . 387 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 394 xv Contents 14. Transient Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395 Simulation Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395 Overview of Transient Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396 Data-Driven vs. Outer Parameter Sweeps . . . . . . . . . . . . . . . . . . . . . . . . Data-Driven Sweep . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Parameter Sweep. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sweeping Multiple Parameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Specifying Data Driven Timesteps . . . . . . . . . . . . . . . . . . . . . . . . . . 397 397 397 398 399 Transient Analysis Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 399 Transient Analysis of an RC Network. . . . . . . . . . . . . . . . . . . . . . . . . . . . 400 Transient Analysis of an Inverter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402 Transient Control Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403 Simulation Speed and Accuracy Using the RUNLVL Option . . . . . . . . . . . . . . 404 RUNLVL Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Interactions Between .OPTION RUNLVL and Other Options . . . . . . 405 406 Numerical Integration Algorithm Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . 408 Dynamic Check Using the .BIASCHK Statement . . . . . . . . . . . . . . . . . . . . . . 410 Troubleshooting: Internal Timestep, Measurement Errors . . . . . . . . . . . . . . . . 412 Troubleshooting ‘Time step Too Small’ Errors . . . . . . . . . . . . . . . . . . . . . 413 Troubleshooting .MEASUREMENT Issues . . . . . . . . . . . . . . . . . . . . . . . 414 15. Spectrum Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 417 Spectrum Analysis (Fourier Transform) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 417 Using the Fourier-Related Statements and Options . . . . . . . . . . . . . . . . 419 Fourier Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 419 Fourier Equation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 419 .FFT Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421 Using Windows in FFT Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422 Examining the FFT Output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428 AM Modulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429 Graphical Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 430 Balanced Modulator and Demodulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 432 Signal Detection Test Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437 Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvi 426 Measuring FFT Output Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437 Contents References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 443 16. AC Small-Signal and Noise Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 445 Using the .AC Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 445 .AC Control Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .AC Command Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446 446 AC Small Signal Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 447 AC Analysis of an RC Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 449 Using .NOISE for Small-Signal Noise Analysis . . . . . . . . . . . . . . . . . . . . . . . . 452 Other AC Analysis Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 455 Using .DISTO for Small-Signal Distortion Analysis . . . . . . . . . . . . . . . . . 456 Using .SAMPLE for Noise Folding Analysis . . . . . . . . . . . . . . . . . . . . . . . 456 17. Linear Network Parameter Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 457 .LIN Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 457 Identifying Ports with the P-element. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458 Using the P-element for Mixed-Mode Measurement . . . . . . . . . . . . . . . . 458 .LIN Input Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 459 .LIN Output Syntax. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .PRINT and .PROBE Statements. . . . . . . . . . . . . . . . . . . . . . . . . . . Hybrid Parameter Calculations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 459 460 462 Multi-Port Scattering (S) Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . 463 Two-Port Transfer and Noise Calculations . . . . . . . . . . . . . . . . . . . . . . . . Equivalent Input Noise Voltage and Current. . . . . . . . . . . . . . . . . . . Equivalent Noise Resistance and Conductance . . . . . . . . . . . . . . . Noise Correlation Impedance and Admittance. . . . . . . . . . . . . . . . . Optimum Matching for Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Noise Figure and Minimum Noise Figure . . . . . . . . . . . . . . . . . . . . . Associated Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Output Format for Group Delay in .sc* Files. . . . . . . . . . . . . . . . . . . Output Format for Two-Port Noise Parameters in .sc* Files . . . . . . . 464 464 465 465 465 465 466 466 466 Noise Parameters in 2-Port and N-Port Networks . . . . . . . . . . . . . . . . . . 467 Hybrid (H) Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 468 Group Delay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 469 Additional Measurements From .LIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 470 Impedance Characterizations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 470 Stability Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 471 xvii Contents Gain Measurements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 471 Matching for Optimal Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 471 Noise Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 471 Two-Port Transfer and Noise Measurements . . . . . . . . . . . . . . . . . . . . . . 472 Output Format for Two-Port Noise Parameters in .sc* Files. . . . . . . . . . . VSWR. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ZIN(i) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . YIN(i) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . K_STABILITY_FACTOR (Rollett Stability Factor) . . . . . . . . . . . . . . . MU_STABILITY_FACTOR (Edwards-Sinsky Stability Factor) . . . . . Maximum Available Power Gain—G_MAX. . . . . . . . . . . . . . . . . . . . Maximum Stable Gain - G_MSG . . . . . . . . . . . . . . . . . . . . . . . . . . . Maximum Unilateral Transducer Power Gain —G_TUMAX . . . . . . . Unilateral Power Gain—GU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Simultaneous Conjugate Match for G_MAX. . . . . . . . . . . . . . . . . . . Equivalent Input Noise Voltage and Current—IN2, VN2, RHON . . . Equivalent Noise Resistance and Conductance—RN, GN . . . . . . . Noise Correlation Impedance and Admittance—ZCOR, YCOR. . . . ZOPT, YOPT, GAMMA_OPT – Optimum Matching for Noise. . . . . . Noise Figure and Noise Figure Minimum—NF, NFMIN . . . . . . . . . . Associated Gain—G_As. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 472 473 473 473 474 474 474 475 475 475 476 477 477 478 478 478 479 Extracting Mixed-Mode Scattering (S) Parameters . . . . . . . . . . . . . . . . . . . . . 480 Defaults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 481 Output File Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 481 Two-Port Parameter Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482 Output Format and Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 483 Prerequisites and Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484 Reported Statistics for the Performance Log (HSPICE RF Only) . . . . . . 484 Errors and Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Via Modeling for PCBs in HSPICE . . . . . . . . . . . . . . . . . . . . . . . . . . 485 485 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 487 18. Statistical Eye Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489 Statistical Eye Analysis Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489 Input Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490 .Print and .Probe Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 491 .Measure Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 492 Output Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Probing Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xviii 483 Features Supported . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 493 493 Contents Printing Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Measurement Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 493 494 Examples, Statistical Analysis Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494 Known Limitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494 19. Timing Analysis Using Bisection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 495 Overview of Bisection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 495 Bisection Methodology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 498 Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 498 Optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 498 Using Bisection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 498 Examining the Command Syntax. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Performing Transient Analyses with Bisections . . . . . . . . . . . . . . . . 500 501 Setup Time Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 502 Input Listing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 502 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 505 Minimum Pulse Width Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 506 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 507 Pushout Bisection Methodology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 507 20. Analyzing Variability and Using the Variation Block . . . . . . . . . . . . . . . . . 511 Overview of Variation on Silicon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 511 Defining Variability in HSPICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 513 Overview of the Variation Block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 514 Variation Block Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 515 General Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 516 Subblocks for Global, Local and Spatial Variations . . . . . . . . . . . . . . . . . Independent Random Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dependent Random Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Absolute Versus Relative Variation. . . . . . . . . . . . . . . . . . . . . . . . . . Variations on Model Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . Variations on Subcircuit Parameters . . . . . . . . . . . . . . . . . . . . . . . . Variations of Element Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . Access Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Spatial Variation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 517 517 518 519 520 521 524 527 528 Special Rules Regarding Variation Block Usage . . . . . . . . . . . . . . . . . . . 529 xix Contents Variation Block Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 529 Group Operator {...} and Subexpressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 531 Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Syntax Extension with Bins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rules for Using the Group Operator. . . . . . . . . . . . . . . . . . . . . . . . . 531 531 532 532 Interconnect Variation in Star-RCXT with the HSPICE Flow . . . . . . . . . . . . . . 533 Variation Block and Statistical Sensitivity Coefficients . . . . . . . . . . . . . . . 534 Usage Example and Input Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1: Interconnect Variation Block. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2: Model Card in the Header Section . . . . . . . . . . . . . . . . . . . . . . . . 3: Parasitic Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 535 535 537 537 Control Options and Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 538 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 540 21. Monte Carlo Analysis Using the Variation Block Flow . . . . . . . . . . . . . . . . 541 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 541 Monte Carlo Analysis in HSPICE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 543 Input Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 544 Monte Carlo-Specific Variation Block Options . . . . . . . . . . . . . . . . . . . . . 546 Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 547 Sampling Options. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 551 Factorial Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 551 One-Factor-at-a-Time Sampling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 552 Latin Hypercube Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 554 554 555 Application Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555 Known Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 556 One Dimensional Monte Carlo Simulation . . . . . . . . . . . . . . . . . . . . . . . . 556 Troubleshooting Monte Carlo Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 556 Independent Random Variable Assignments . . . . . . . . . . . . . . . . . . . . . . 556 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xx 553 External Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Usage Model for External Sampling. . . . . . . . . . . . . . . . . . . . . . . . . Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 559 Contents 22. Mismatch Analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 561 Mismatch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 561 DCMatch Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 562 Input Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 563 DCMatch Table Output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 564 Output Using .PROBE and .MEASURE Commands . . . . . . . . . . . . . . . . Syntax for .PROBE Command for DCMatch . . . . . . . . . . . . . . . . . . Syntax for .MEASURE Command . . . . . . . . . . . . . . . . . . . . . . . . . . 566 566 567 DCMatch Example Netlist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 568 ACMatch Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 569 Input Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 570 ACMatch Table Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Output from .PROBE and .MEASURE Commands for ACMatch . . . 571 572 Application Considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 574 Mismatch Compared to Monte Carlo Analysis . . . . . . . . . . . . . . . . . . . . . 575 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 576 23. Exploration Block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 577 Exploration Block Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 577 Usage Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 578 Multiple Instantiations of the Same Cell or Subcircuit . . . . . . . . . . . . . . . 578 Specifying Relationships between Devices . . . . . . . . . . . . . . . . . . . . . . . 579 Specifying Relationships between Properties . . . . . . . . . . . . . . . . . . . . . Subcircuits and Elements Supported for Exploration . . . . . . . . . . . . 579 580 Flow Using an External Exploration Tool . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 581 Export Phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 581 Definition Phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 582 Exploration Phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 582 Netlist Export . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 583 Exploration Block Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 584 Syntax Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Exploration Block Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Parameters Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Device Relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Secondary Element Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . Secondary Device Parameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Same-Circuit Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 584 584 587 587 587 588 588 xxi Contents Derived Device Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Parameters Defined Outside the Exploration Block . . . . . . . . . . . . 589 589 Area Measurement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rules for Area Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 589 590 Processing Netlist Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 591 Export File Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 592 Syntax Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 592 Executing Exploration in HSPICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 593 EXCommand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Option: Export . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Data Block. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Action 594 Exploration Data Block Syntax. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 594 Exploration Block Interactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 595 Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 595 Netlist Export . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 595 24. Optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 597 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 597 Optimization Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 598 Curve Fit Optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 599 Goal Optimization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 599 Timing Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 600 Optimization Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 600 Optimizing Analysis (.DC, .TRAN, .AC) . . . . . . . . . . . . . . . . . . . . . . . . . . 601 Optimization Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 602 MOS Level 3 Model DC Optimization. . . . . . . . . . . . . . . . . . . . . . . . . . . . Input Netlist File for Level 3 Model DC Optimization . . . . . . . . . . . . 602 603 MOS Level 13 Model DC Optimization. . . . . . . . . . . . . . . . . . . . . . . . . . . DC Optimization Input Netlist File for Level 13 Model . . . . . . . . . . . 605 605 RC Network Optimization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Optimization Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Optimized Parameters OPTRC . . . . . . . . . . . . . . . . . . . . . . . . . . . . 606 606 608 Optimizing CMOS Tristate Buffer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Input Netlist File to Optimize a CMOS Tristate Buffer. . . . . . . . . . . . 609 610 BJT S-parameters Optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 612 BJT Model DC Optimization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxii 598 Simulation Accuracy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 614 Contents Optimizing GaAsFET Model DC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 616 Optimizing MOS Op-amp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 617 25. RC Reduction and Post-Layout Simulation . . . . . . . . . . . . . . . . . . . . . . . . 621 Linear Acceleration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 621 PACT Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 623 PI Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 623 Linear Acceleration Control Options Summary . . . . . . . . . . . . . . . . . . . . . . . . 624 Supporting Parasitic L- and K-elements. . . . . . . . . . . . . . . . . . . . . . . . . . 625 26. MOSFET Model Reliability Analysis (MOSRA) . . . . . . . . . . . . . . . . . . . . . . 627 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 627 Usage Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Example Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 627 628 .MOSRA, .MOSRAPRINT, .MODEL, and .APPENDMODEL Commands . . . . 629 .MOSRA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 629 .MOSRAPRINT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 634 .MODEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Synopsys LEVEL1 mosra model, NBTI for PMOS . . . . . . . . . . . . . Synopsys LEVEL1 mosra model, HCI for NMOS and PMOS . . . . . 634 636 640 .APPENDMODEL. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .OPTION APPENDALL. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 641 642 Simulation Output File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 643 RADEG Output Sorting (.OPTION MOSRASORT) . . . . . . . . . . . . . . . . . 644 Known Limitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 644 Part IV: Simulation Applications 27. Performing Digital Cell Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . 647 Performing Basic Cell Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 648 Rise, Fall, and Delay Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 648 Delay versus Fanout. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651 Pin Capacitance Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 652 Op-amp Characterization of LM124 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 653 Performing Advanced Cell Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . 654 xxiii Contents Cell Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28. Behavioral Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 661 Behavioral Design Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 662 Using Behavioral Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 662 Controlled Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 664 Libraries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 664 Voltage and Current Controlled Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 664 Modeling with Digital Behavioral Components. . . . . . . . . . . . . . . . . . . . . . . . . 665 Behavioral AND and NAND Gates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 665 Behavioral D-Latch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 665 Behavioral Double-Edge Triggered Flip-Flop . . . . . . . . . . . . . . . . . . . . . . 667 Calibrating Digital Behavioral Components . . . . . . . . . . . . . . . . . . . . . . . . . . . 669 Building Behavioral Lookup Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Subcircuit Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Behavioral N-Channel MOSFET . . . . . . . . . . . . . . . . . . . . . . . . . . . Creating a Behavioral Inverter Lookup Table . . . . . . . . . . . . . . . . . . 669 670 670 671 Optimizing Behavioral CMOS Inverters . . . . . . . . . . . . . . . . . . . . . . . . . . 673 Optimizing Behavioral Ring Oscillators . . . . . . . . . . . . . . . . . . . . . . . . . . Example Five-Stage Ring Oscillator. . . . . . . . . . . . . . . . . . . . . . . . . 675 675 Analog Behavioral Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 675 Behavioral Differentiator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 677 Ideal Transformer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 678 Behavioral Amplitude Modulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 679 Behavioral Data Sampler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 680 Op-Amps, Comparators, and Oscillators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 680 741 Op-Amp from Controlled Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . 680 Inverting Comparator with Hysteresis . . . . . . . . . . . . . . . . . . . . . . . . . . . 683 Voltage-Controlled Oscillator (VCO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 684 LC Oscillator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 686 Phase-Locked Loops (PLL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 689 Phase Detector, with Multi-Input NAND Gates. . . . . . . . . . . . . . . . . . . . . 689 Phase Locked Loop Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 690 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxiv 656 694 Contents 29. Modeling Filters and Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 695 Transient Modeling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 695 Using G- and E-elements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 696 Laplace Transform Function Call . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 696 Element Statement Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 699 Z Transform Function Call . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 700 G- and E-element Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 701 Laplace Band-Reject Filter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 701 Laplace Low-Pass Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 703 Circular Convolution Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30-Degree Phase Shift Circuit File . . . . . . . . . . . . . . . . . . . . . . . . . . 705 706 706 Laplace and Pole-Zero Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 707 Laplace Transform (LAPLACE) Function . . . . . . . . . . . . . . . . . . . . . . . . . General Form of the Transfer Function. . . . . . . . . . . . . . . . . . . . . . . Finding the Transfer Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Determining the Laplace Coefficients . . . . . . . . . . . . . . . . . . . . . . . 707 707 708 711 Laplace Transform POLE (Pole/Zero) Function . . . . . . . . . . . . . . . . . . . . POLE Function Call . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . General Form of the Transfer Function. . . . . . . . . . . . . . . . . . . . . . . Reduced Form of the Transfer Function . . . . . . . . . . . . . . . . . . . . . . RC Line Modeling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 715 715 715 716 719 AWE Transfer Function Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 721 Y-parameter Line Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 723 Comparison of Circuit and Pole/Zero Models . . . . . . . . . . . . . . . . . . . . . Simulation Time Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 726 726 Modeling Switched Capacitor Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 729 Switched Capacitor Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 729 Switched Capacitor Filter Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 730 Input File for Switched Capacitor Filter . . . . . . . . . . . . . . . . . . . . . . . . . . 732 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 734 30. Simulation of Random Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 735 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 735 Characteristics of Random Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 736 Probability Distribution Function versus Power Spectral Density . . . . . . . 736 Multiple Noise Sources in a Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 739 xxv Contents Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 741 Noise Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 741 Thermal Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 741 Flicker Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 743 Shot Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 746 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 747 Component Noise Models and HSPICE/HSPICE RF Noise Simulation . . . . . 747 Element Noise Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 747 HSPICE and HSPICE RF Noise Simulation. . . . . . . . . . . . . . . . . . . . . . . 748 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 753 31. Using Verilog-A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 755 Getting Started. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 756 Introduction to Verilog-A. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 760 Verilog-A Module Template . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 760 Data Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 761 Analog Operators and Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Example: Using idt to Perform Time Integral of an Argument . . . . . 763 764 Mathematical Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 765 Transcendental Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 765 AC Analysis Stimuli . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 766 Noise Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 767 Analog Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 767 Timestep and Simulator Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 768 System Tasks and I/O Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 769 Simulator Environment Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 773 Module Hierarchy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 774 Parameter Sets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 774 Simulation with Verilog-A Modules. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 774 Loading Verilog-A Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 775 .hdl Command Module Selection and Module Alias. . . . . . . . . . . . . . . . . 776 Verilog-A File Loading Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . 777 Instantiating Verilog-A Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 778 Using Model Cards with Verilog-A Modules . . . . . . . . . . . . . . . . . . . . . . . 779 Restrictions on Verilog-A Module Names. . . . . . . . . . . . . . . . . . . . . . . . . 781 Overriding Subcircuits with Verilog-A Modules . . . . . . . . . . . . . . . . . . . . xxvi 776 Verilog-A File Search Path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 781 Contents Netlist Option . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Command-line Option . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Disabling .OPTION vamodel with .OPTION spmodel (HSPICE Only) Using Vector Buses or “Ports” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using Integer Parameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Implicit Parameter M Support. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Module and Parameter Name Case Sensitivity . . . . . . . . . . . . . . . . 781 782 783 784 784 784 785 Instantiating Primitive Devices inside Verilog-A Modules. . . . . . . . . . . . . . . . . 785 Instantiating HSPICE subcircuits inside Verilog-A Modules. . . . . . . . . . . . . . . 787 Output Simulation Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 788 V() and I() Access Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 789 Output Bus Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 790 Output Internal Module Variables (HSPICE only) . . . . . . . . . . . . . . . . . . 790 Output Module Parameters (HSPICE only) . . . . . . . . . . . . . . . . . . . . . . . 792 Using Wildcards in Verilog-A (HSPICE only) . . . . . . . . . . . . . . . . . . . . . . 792 Port Probing and Branch Current Reporting Conventions . . . . . . . . . . . . 793 Unsupported Output Function Features. . . . . . . . . . . . . . . . . . . . . . . . . . 793 Running 32-bit HSPICE Verilog-A on Linux x86_64 . . . . . . . . . . . . . . . . . . . . 794 Compiling Verilog-A Files on Demand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 795 Setting Options for the HSPICE Verilog-A Compiler . . . . . . . . . . . . . . . . . . . . 795 The Compiled Model Library Cache . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cache Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Deleting the Cache. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 796 796 797 Using the Standalone Compiler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 797 Troubleshooting Environment Setting Issues . . . . . . . . . . . . . . . . . . . . . . . . . . 798 Unsupported Language Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 798 Known Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Part V: 791 Case Sensitivity in Simulation Data Output . . . . . . . . . . . . . . . . . . . . . . . 802 Demonstration Files/Errors-Warnings 31. Running Demonstration Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 807 Using the Demo Directory Tree . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 807 Two-Bit Adder Demo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 809 One-Bit Subcircuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 809 xxvii Contents MOS Two-Bit Adder Input File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 810 MOS I-V and C-V Plotting Demo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 810 Printing Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 811 MOS I-V and C-V Plot Example Input File . . . . . . . . . . . . . . . . . . . . . . . . 815 CMOS Output Driver Demo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 815 Strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 816 CMOS Output Driver Example Input File . . . . . . . . . . . . . . . . . . . . . . . . . 820 Temperature Coefficients Demo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 820 Input File for Optimized Temperature Coefficients . . . . . . . . . . . . . . . . . . 821 Optimization Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 822 Modeling Wide-Channel MOS Transistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . 822 Listing of Demonstration Input Files. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 824 HSPICE Integration to CadenceTM Virtuoso® Analog Design Environment Tutorial Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 826 Applications of General Interest Examples . . . . . . . . . . . . . . . . . . . . . . . 826 Behavioral Application Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 828 Benchmark Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 830 Bisection-Timing Analysis Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . 830 BJT and Diode Examples. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 831 Cell Characterization Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 832 Circuit Optimization Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 833 Device Optimization Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 833 Encryption Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 834 Fourier Analysis Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 834 Filters Examples. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 836 IBIS / Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 837 Magnetics Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 838 MOSFET Device Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 838 Signal Integrity Examples. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 840 Sources Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 840 S-parameter Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 841 Transmission Lines Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 842 Transmission (W-element) Line Examples . . . . . . . . . . . . . . . . . . . . . . . . 842 Variability Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxviii 843 Verilog-A Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 843 Contents 32. Warning/Error Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 845 Warning Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 845 Topology Warnings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Topology Integrity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . No DC Path to Ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Duplicate Initialization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 845 845 846 846 Model Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Zero or Negative Conductance . . . . . . . . . . . . . . . . . . . . . . . . . . . . Encryption-Related Warnings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Model Binning Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Key Model Parameter Checking . . . . . . . . . . . . . . . . . . . . . . . . . . . . Parameter Expression Warning . . . . . . . . . . . . . . . . . . . . . . . . . . . . 846 846 847 847 847 847 Control Option Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . RUNLVL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ACCURATE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FAST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . GMIN, GMINDC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 848 848 848 848 848 Device Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Device Geometry Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Device Parameter Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 849 849 849 Analysis Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Transient. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bisection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Measure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .DC and .OP Analysis Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . 849 849 849 850 850 Error Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 851 Topology Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 851 Model Errors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 853 853 856 857 Analysis Options: DIAGNOSTIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 858 Transient Analysis Errors and Solutions. . . . . . . . . . . . . . . . . . . . . . . . . . Transient Analysis Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 859 859 Exit Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. 852 Analysis Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .DC and Operating Convergence Errors . . . . . . . . . . . . . . . . . . . . . Convergence/Conductance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Convergence/Diode Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . 861 Statistical Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 863 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 863 xxix Contents Application of Statistical Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Analytical Model Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 865 Temperature Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 867 .TEMP Statement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 868 Worst Case Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 868 Model Skew Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using Skew Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Skew File Interface to Device Models. . . . . . . . . . . . . . . . . . . . . . . . 868 870 872 Getting Started with Traditional Monte Carlo Simulations . . . . . . . . . . . . . . . . 873 Traditional Monte Carlo Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 875 Monte Carlo Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 876 Monte Carlo Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 878 .PARAM Distribution Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 878 Monte Carlo Parameter Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 881 Monte Carlo Examples. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gaussian, Uniform, and Limit Functions . . . . . . . . . . . . . . . . . . . . . Major and Minor Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . RC Time Constant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Switched Capacitor Filter Design . . . . . . . . . . . . . . . . . . . . . . . . . . . 881 881 884 885 886 Worst Case and Monte Carlo Sweep Example . . . . . . . . . . . . . . . . . . . . . . . . 888 Transient Sigma Sweep Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Operating-Point Results in Transient Analysis . . . . . . . . . . . . . . . . . 890 890 Monte Carlo Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 891 Simulating the Effects of Global and Local Variations with Monte Carlo . . . . . 898 Variations Specified on Geometrical Instance Parameters . . . . . . . . . . . 898 Variations Specified in the Context of Subcircuits . . . . . . . . . . . . . . . . . . 900 Variations on a Model Parameter Using a Local Model in Subcircuit. . . . 901 Indirect Variations on a Model Parameter . . . . . . . . . . . . . . . . . . . . . . . . 901 Variations Specified on Model Parameters . . . . . . . . . . . . . . . . . . . . . . . 902 Variations Specified Using DEV and LOT . . . . . . . . . . . . . . . . . . . . . . . . 902 Combinations of Variation Specifications . . . . . . . . . . . . . . . . . . . . . . . . . 903 Variation on Model Parameters as a Function of Device Geometry. . . . . 904 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 905 Full Simulation Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 907 Simulation Example Using WaveView . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxx 864 Simulating Circuit and Model Temperatures . . . . . . . . . . . . . . . . . . . . . . . . . . B. 864 907 Contents Input Netlist and Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Execution and Output Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Example.ic0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Example.mt0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Example.lis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Example.pa0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Example.st0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 909 910 910 911 914 915 View HSPICE Results in WaveView. . . . . . . . . . . . . . . . . . . . . . . . . . . . . C. 907 918 Obsolete HSPICE Functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 925 U-element Digital and Mixed Mode Stimuli . . . . . . . . . . . . . . . . . . . . . . . . . . . 925 U-element Digital Input Elements and Models . . . . . . . . . . . . . . . . . . . . . General Form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Model Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Digital-to-Analog Input Model Parameters . . . . . . . . . . . . . . . . . . . . 925 926 926 927 U Element Digital Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Model Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Analog-to-Digital Output Model Parameters. . . . . . . . . . . . . . . . . . . 928 929 929 Replacing Sources With Digital Inputs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 931 .NET Parameter Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 933 Network Analysis Example: Bipolar Transistor. . . . . . . . . . . . . . . . . . . . . 936 .NET Parameter Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 936 Bandpass Netlist: Network Analysis Results . . . . . . . . . . . . . . . . . . . . . . 937 Behavioral Modeling, Obsolete Functionality. . . . . . . . . . . . . . . . . . . . . . . . . . 939 Digital Stimulus Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 939 Op-Amp Subcircuit Generators (Behavioral Modeling . . . . . . . . . . . . . . . 940 Op-Amp Model Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 940 Op-Amp Element Statement Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . 941 Op-Amp .MODEL Statement Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . Op-Amp Model Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Op-Amp Model Parameter Defaults . . . . . . . . . . . . . . . . . . . . . . . . . 942 942 948 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 949 Unity Gain Resistor Divider Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 951 Behavioral Tunnel Diode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 951 Behavioral Silicon-Controlled Rectifier (SCR) . . . . . . . . . . . . . . . . . . . . . 952 Behavioral Triode Vacuum Tube Subcircuit . . . . . . . . . . . . . . . . . . . . . . . 953 xxxi Contents D. 955 Controlling the Simulation with RUNLVL=0 . . . . . . . . . . . . . . . . . . . . . . . . . . . 955 Simulation Accuracy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Timestep Control for Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Guidelines for Choosing Accuracy Options . . . . . . . . . . . . . . . . . . . 956 956 957 Selecting Timestep Control Algorithms . . . . . . . . . . . . . . . . . . . . . . . . . . Iteration Count Dynamic Timestep . . . . . . . . . . . . . . . . . . . . . . . . . . Local Truncation Error Dynamic Timestep . . . . . . . . . . . . . . . . . . . . DVDT Dynamic Timestep . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 957 958 958 958 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxii Transient Simulation with RUNLVL=0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 961 About this User Guide This guide describes how to use HSPICE to simulate and analyze your circuit designs. Inside this Guide This user guide contains the chapters described below. For descriptions of the other manuals in the HSPICE documentation set, see the next section, The HSPICE Documentation Set. Chapter Description Part 1: Introduction to HSPICE Chapter 1, Overview Describes HSPICE features and the simulation process. Chapter 2, Setup Describes the environment variables and standard I/O files. Chapter 3, Startup and Simulation Describes the invocation commands and types of simulation and analysis available in HSPICE. Chapter 4, Input Netlist and Data Entry Describes the input netlist file and methods of entering data. Chapter 5, Using Interactive Mode Provides details on invoking and using interactive mode. Chapter 6, HSPICE GUI for Windows Describes the graphical user interface available on the Windows platform only. Chapter 7, Library and Data Encryption Describes the three methods available to create encrypted files. Part 2: Elements and Devices HSPICE® User Guide: Simulation and Analysis B-2008.09 xxxiii Inside this Guide Chapter Description Chapter 8, Elements Describes the syntax for the basic elements of a circuit netlist in HSPICE or HSPICE RF. Chapter 9, Sources and Stimuli Describes element and model statements for independent sources, dependent sources, analogto-digital elements, and digital-to-analog elements. Chapter 10, Parameters and Functions Describes how to use parameters within an HSPICE netlist. Chapter 11, Simulation Output Describes how to use output format statements and variables to display steady state, frequency, and time domain simulation results. Part 3: Analyses Chapter 12, Initializing DC/ Operating Point Analysis Chapter 13, Pole/Zero Analysis Describes how to use pole/zero analysis in HSPICE or HSPICE RF to study the behavior of linear, time-invariant networks. Chapter 14, Transient Analysis Describes how to use transient analysis to compute the circuit solution. Chapter 15, Spectrum Analysis Describes how to use spectrum analysis to provide the highest FFT accuracy with minimal overhead in simulation time. Chapter 16, AC Small-Signal and Noise Analysis Describes how to perform AC and noise small signal analysis. Chapter 17, Linear Network Parameter Analysis Describes how to perform an AC sweep to extract small-signal linear network parameters. Chapter 18, Statistical Eye Analysis Describes how to perform statistical eye diagram analysis using .STATEYE. Chapter 19, Timing Analysis Using Bisection xxxiv Describes DC initialization and operating point analysis. Describes how to use the bisection function in timing optimization. HSPICE® User Guide: Simulation and Analysis B-2008.09 Inside this Guide Chapter Description Chapter 20, Analyzing Variability and Using the Variation Block Describes the use model and structure of the Variation Block in HSPICE. Chapter 21, Monte Carlo Analysis Using the Variation Block Flow Describes Monte Carlo analysis in HSPICE. Chapter 22, Mismatch Analyses Describes the use of DCmatch analysis in HSPICE. Chapter 23, Exploration Block Describes the use of the Exploration Block in HSPICE. Chapter 24, Optimization Describes optimization in HSPICE for optimizing electrical yield. Chapter 25, RC Reduction and Post-Layout Simulation Describes RC network reduction in HSPICE. Chapter 26, MOSFET Model Reliability Analysis (MOSRA) Describes reliability analysis for MOSFET devices. Part 4: Simulation Applications Chapter 27, Performing Digital Cell Characterization Describes how to characterize cells in a datadriven analysis. Chapter 28, Behavioral Modeling Describes how to substitute abstract circuit models for lower-level descriptions of analog functions. Chapter 29, Modeling Filters and Networks Describes modeling filters and networks, including Laplace transforms. Chapter 30, Simulation of Random Noise Describes the characteristics of random signals, types of noise, component noise models, and noise simulation. Chapter 31, Using Verilog-A Describes how to use Verilog-A in HSPICE and HSPICE RF simulations. Part 5: Demonstration Files/Errors-Warnings HSPICE® User Guide: Simulation and Analysis B-2008.09 xxxv The HSPICE Documentation Set Chapter Description Chapter 31, Running Demonstration Files Contains examples of basic file construction techniques, advanced features, and simulation tricks. Lists and describes several HSPICE and input files. Chapter 32, Warning/Error Messages Provides an overview of the type of warnings and error messages that HSPICE prints and troubleshooting measures to take when possible. Appendix A, Statistical Analysis Describes the features available in HSPICE for statistical analysis before the Y-2006.03 release. Appendix B, Full Simulation Example Contains information and sample input netlist for a full simulation example in HSPICE. Appendix C, Obsolete HSPICE Functionality Describes out-of-date, rarely used, or deemphasized functionality. Appendix D, Transient Simulation with RUNLVL=0 Describes running a transient simulation with .OPTION RUNLVL=0. The HSPICE Documentation Set This manual is a part of the HSPICE documentation set, which includes the following manuals: The HSPICE Documentation Set This manual is a part of the HSPICE documentation set, which includes the following manuals: Manual HSPICE User Guide: Simulation and Analysis xxxvi Description Describes how to use HSPICE to simulate and analyze your circuit designs, and includes simulation applications. This is the main HSPICE user guide. HSPICE® User Guide: Simulation and Analysis B-2008.09 The HSPICE Documentation Set Manual Description HSPICE User Guide: Signal Integrity Describes how to use HSPICE to maintain signal integrity in your chip design. HSPICE User Guide: RF Analysis Describes how to use special set of analysis and design capabilities added to HSPICE to support RF and high-speed circuit design. HSPICE Reference Manual: Commands and Control Options Provides reference information for HSPICE and HSPICE RF commands and options. HSPICE Reference Manual: Elements and Device Models Describes standard models you can use when simulating your circuit designs in HSPICE, including passive devices, diodes, JFET and MESFET devices, and BJT devices. HSPICE Reference Manual: MOSFET Models Describes available MOSFET models you can use when simulating your circuit designs in HSPICE. HSPICE Integration to CadenceTM Virtuoso® Analog Design Environment User Guide Describes use of the HSPICE simulator integration to the Cadence tool. AMS Discovery Simulation Interface Guide for HSPICE Describes use of the Simulation Interface with other EDA tools for HSPICE. AvanWaves User Guide Describes the AvanWaves tool, which you can use to display waveforms generated during HSPICE circuit design simulation. Searching Across the HSPICE Documentation Set You can access the PDF format documentation from your install directory for the current release by entering -docs on the terminal command line when the HSPICE tool is open. Synopsys includes an index with your HSPICE documentation that lets you search the entire HSPICE documentation set for a particular topic or keyword. In a single operation, you can instantly generate a list of hits that are hyper- HSPICE® User Guide: Simulation and Analysis B-2008.09 xxxvii Conventions linked to the occurrences of your search term. For information on how to perform searches across multiple PDF documents, see the HSPICE release notes. Note: To use this feature, the HSPICE documentation files, the Index directory, and the index.pdx file must reside in the same directory. (This is the default installation for Synopsys documentation.) Also, Adobe Acrobat must be invoked as a standalone application rather than as a plug-in to your web browser. You can also invoke HSPICE and RF documentation in a browser-based help system by entering-help on your terminal command line when the HSPICE tool is open. This provides access to all the HSPICE manuals with the exception of the AvanWaves User Guide which is available in PDF format only. Known Limitations and Resolved STARs You can find information about known problems and limitations and resolved Synopsys Technical Action Requests (STARs) in the HSPICE Release Notes shipped with this release. For updates, go to SolvNet. To access the HSPICE Release Notes: 1. Go to https://solvnet.synopsys.com/ReleaseNotes. (If prompted, enter your user name and password. If you do not have a Synopsys user name and password, follow the instructions to register with SolvNet.) 2. Select Download Center> HSPICE> version number> Release Notes. Conventions The following typographical conventions are used in Synopsys HSPICE documentation. Convention Courier Indicates command syntax. Italic Indicates a user-defined value, such as object_name. Bold xxxviii Description Indicates user input—text you type verbatim—in syntax and examples. HSPICE® User Guide: Simulation and Analysis B-2008.09 Customer Support Convention Description Denotes optional parameters, such as: write_file [-f filename] ... Indicates that parameters can be repeated as many times as necessary: pin1 pin2 ... pinN | Indicates a choice among alternatives, such as low | medium | high + Indicates a continuation of a command line. / Indicates levels of directory structure. Edit > Copy Indicates a path to a menu command, such as opening the Edit menu and choosing Copy. Control-c Indicates a keyboard combination, such as holding down the Control key and pressing c. Customer Support Customer support is available through SolvNet online customer support and through contacting the Synopsys Technical Support Center. Accessing SolvNet SolvNet includes an electronic knowledge base of technical articles and answers to frequently asked questions about Synopsys tools. SolvNet also gives you access to a wide range of Synopsys online services, which include downloading software, viewing Documentation on the Web, and entering a call to the Support Center. To access SolvNet: 1. Go to the SolvNet Web page at http://solvnet.synopsys.com. 2. If prompted, enter your user name and password. (If you do not have a Synopsys user name and password, follow the instructions to register with SolvNet.) HSPICE® User Guide: Simulation and Analysis B-2008.09 xxxix Customer Support If you need help using SolvNet, click Help on the SolvNet menu bar. Contacting the Synopsys Technical Support Center If you have problems, questions, or suggestions, you can contact the Synopsys Technical Support Center in the following ways: ■ Open a call to your local support center from the Web by going to http://solvnet.synopsys.com/EnterACall (Synopsys user name and password required). ■ Send an e-mail message to your local support center. • • ■ E-mail support_center@synopsys.com from within North America. Find other local support center e-mail addresses at http://www.synopsys.com/support/support_ctr. Telephone your local support center. • • Call (650) 584-4200 from Canada. • xl Call (800) 245-8005 from within the continental United States. Find other local support center telephone numbers at http://www.synopsys.com/support/support_ctr. HSPICE® User Guide: Simulation and Analysis B-2008.09 Part: 1 Introduction to HSPICE This manual is organized according to the following five Parts: ■ Introduction to HSPICE ■ Elements and Devices ■ Analyses ■ Simulation Applications ■ Demonstration Files/Errors-Warnings Part 1 presents the following chapters /topics: ■ Chapter 1, Overview ■ Chapter 2, Setup ■ Chapter 3, Startup and Simulation ■ Chapter 4, Input Netlist and Data Entry ■ Chapter 5, Using Interactive Mode ■ Chapter 6, HSPICE GUI for Windows ■ Chapter 7, Library and Data Encryption HSPICE® User Guide: Simulation and Analysis B-2008.09 1 2 HSPICE® User Guide: Simulation and Analysis B-2008.09 1 Overview 1 Describes HSPICE features and the simulation process. Synopsys HSPICE is an optimizing analog circuit simulator. You can use it to simulate electrical circuits in steady-state, transient, and frequency domains. HSPICE is unequalled for fast, accurate circuit and behavioral simulation. It facilitates circuit-level analysis of performance and yield, by using Monte Carlo, worst-case, parametric sweep, and data-table sweep analyses, and employs the most reliable automatic-convergence capability (see Figure 1). Transmission Line Signal Integrity Monte Carlo Worst-Case Analysis HSPICE Circuit Cell Optimization Cell Characterization Incremental Optimization AC, DC, Transient Figure 1 Synopsys HSPICE Design Features HSPICE forms the cornerstone of a suite of Synopsys tools and services that allows accurate calibration of logic and circuit model libraries to actual silicon performance. HSPICE® User Guide: Simulation and Analysis B-2008.09 3 Chapter 1: Overview HSPICE Varieties The size of the circuits that HSPICE can simulate is limited only by memory. As a 32-bit application, HSPICE can address a maximum of 2Gb or 4Gb of memory, depending on your system. For a description of commands that you can include in your HSPICE netlist, see the HSPICE and HSPICE RF Netlist Commands chapter in the HSPICE Reference Manual: Commands and Control Options. These topics are covered in the following sections: ■ HSPICE Varieties ■ Features ■ HSPICE Features for Running Higher-Level Simulations ■ Simulation Structure ■ Experimental Methods Supported by HSPICE ■ Simulation Process Overview HSPICE Varieties Synopsys HSPICE is available in two varieties: ■ HSPICE ■ HSPICE RF Like traditional SPICE simulators, HSPICE is faster and has more capabilities than typical SPICE simulators. HSPICE accurately simulates, analyzes, and optimizes circuits from DC to microwave frequencies that are greater than 100 GHz. HSPICE is ideal for cell design and process modeling. It is also the tool of choice for signal-integrity and transmission-line analysis. HSPICE RF is newer and offers many (but not all) HSPICE simulation capabilities and HSPICE RF simulations of radio-frequency (RF) devices, which HSPICE does not support. This guide describes all of the features that HSPICE supports. HSPICE RF supports some—but not all—of these features as well. For descriptions of HSPICE RF features and a list of the differences between HSPICE and HSPICE RF, see the HSPICE RF Features and Functionality chapter in the HSPICE User Guide: RF Analysis. 4 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 1: Overview Features Features Synopsys HSPICE is compatible with most SPICE variations and has the following additional features: ■ Superior convergence ■ Accurate modeling, including many foundry models ■ Hierarchical node naming and reference ■ Circuit optimization for models and cells, with incremental or simultaneous multiparameter optimizations in AC, DC, and transient simulations ■ Interpreted Monte Carlo and worst-case design support ■ Input, output, and behavioral algebraics for cells with parameters ■ Cell characterization tools to characterize standard cell libraries ■ Geometric lossy-coupled transmission lines for PCB, multi-chip, package, and IC technologies ■ Discrete component, pin, package, and vendor IC libraries ■ Interactive graphing and analysis of multiple simulation waveforms by using with waveform viewers such as WaveView Analyzer and CosmosScope ■ Flexible license manager that allocates licenses intelligently based on run status and user-specified job priorities If you suspend a simulation job (Ctrl-Z), the load sharing facility (LSF) license manager signals HSPICE to release that job’s license. This frees the license for another simulation job, or so the stopped job can reclaim the license and resume. You can also prioritize simulation jobs you submit; LSF automatically suspends low-priority simulation jobs to run high-priority jobs. When the high-priority job completes, LSF releases the license back to the lower-priority job, which resumes from where it was suspended. To resume the LSF job, on the same terminal, type either fg or bg. ■ A number of circuit analysis types (see Figure 2 on page 6) and device modeling technologies. HSPICE® User Guide: Simulation and Analysis B-2008.09 5 Chapter 1: Overview Features ■ Ability to integrate models with the Custom CMI for which HSPICE or HSPICE RF uses a dynamically-linked shared library. Consult your HSPICE technical support team for access to the HSPICE CMI application note and source code. ■ Ability to invoke the TMI flow using proprietary TSMC model files and compiled libraries. Jointly developed by Synopsys and TSMC the TMI technology and API provides a compact model with additional instance parameters and equations for an advanced modeling approach to support TSMC’s extension of the standard BSIM4 model. Modeling API code is written in C and available in a compiled format for HSPICE and HSIM to link to during the simulation. TMI-required settings to invoke the flow and the location of a .so file are set by TSMC. The API also performs automatic platform selection on the .so file. Both HSPICE and HSIM provide the tool binaries and support the same *.so file. Use the existing HSPICE and HSIM commands to run the simulation. (Contact Synopsys Technical Support for further information.) See also the HSPICE Reference Manual: Commands and Control Options for .OPTION TMI FLAG and .OPTION TMIPATH. 40+ Industrial and Academic Models SPICE BJT Magnetics MOS Common Model Interface Lossy Transmission Lines Device Models SOI IBIS Mixed Signal JFET/GaAsFET Diode Tunnel Diode Figure 2 6 Synopsys HSPICE Modeling Technologies HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 1: Overview HSPICE Features for Running Higher-Level Simulations HSPICE Features for Running Higher-Level Simulations Simulations at the integrated circuit level and at the system level require careful planning of the organization and interaction between transistor models and subcircuits. Methods that worked for small circuits might have too many limitations when applied to higher-level simulations. You can use the following HSPICE features to organize how simulation circuits and models run: ■ Explicit include files – .INCLUDE statement. ■ Implicit include files – .OPTION SEARCH=‘lib_directory’. ■ Algebraics and parameters for devices and models – .PARAM statement. ■ Parameter library files – .LIB statement. ■ Automatic model selector – LMIN, LMAX, WMIN, and WMAX model parameters. ■ Parameter sweep – sweep analysis statements. ■ Statistical analysis – sweep monte analysis statements. ■ Multiple alternative –.ALTER statement. ■ Automatic measurements – .MEASURE statement. ■ Condition-controlled netlists (IF-ELSEIF-ELSE-ENDIF statements). Simulation Structure Experimental Methods Supported by HSPICE Typically, you use experiments to analyze and verify complex designs. These experiments can be simple sweeps, more complex Monte Carlo and optimization analyses, or setup and hold violation analyses of DC, AC, and transient conditions. HSPICE® User Guide: Simulation and Analysis B-2008.09 7 Chapter 1: Overview Simulation Structure Simulation Experiment Single point Analysis Optimization Initial Conditions Circuit Transient Results Analysis Timing Violations Statistical Worst Case Sweep DC Library Stimuli AC Options Figure 3 Simulation Program Structure For each simulation experiment, you must specify tolerances and limits to achieve the desired goals, such as optimizing or centering a design. Common factors for each experiment are: ■ process ■ voltage ■ temperature ■ parasitics HSPICE supports two experimental methods: ■ Single point – a simple procedure that produces a single result, or a single set of output data. ■ Multipoint – performs an analysis (single point) sweep for each value in an outer loop (multipoint) sweep. The following are examples of multipoint experiments: ■ ■ 8 Process variation – Monte Carlo or worst-case model parameter variation . Element variation – Monte Carlo or element parameter sweeps. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 1: Overview Simulation Structure ■ Voltage variation – VCC, VDD, or substrate supply variation. ■ Temperature variation – design temperature sensitivity. ■ Timing analysis – basic timing, jitter, and signal integrity analysis. ■ Parameter optimization – balancing complex constraints, such as speed versus power, or frequency versus slew rate versus offset (analog circuits). Simulation Process Overview Figure 4 shows the HSPICE simulation process. HSPICE® User Guide: Simulation and Analysis B-2008.09 9 Chapter 1: Overview Simulation Structure 1. Invocation 2. Run script 3. Licensing hspice -i demo.sp -o demo.lis Select version Select best architecture Run HSPICE Find license file in LM_LICENSE_FILE Get FLEXlm license token 4. Simulation configuration Read ~/meta.cfg or Read <installdir>/meta.cfg 5. Design input Read input file: demo.sp Open temp. files in \$tmpdir Open output file Read hspice.ini file 6. Library input Read .INCLUDE statement files Read .LIB Read implicit include (.inc) files 7. Operating point initialization Read .ic file (optional) Find operating point Write .ic file (optional) 8. Multipoint analysis Open measure data files .mt0 Initialize outer loop sweep Set analysis temperature 9. Single point analysis Open graph data file .tr0 Perform analysis sweep 10. Worst case .ALTER 11. Clean up Figure 4 10 Process library delete/add Process parameter and topology changes Close all files Release all tokens Simulation Process HSPICE® User Guide: Simulation and Analysis B-2008.09 2 2 Setup Describes the environment variables, standard I/O files, invocation commands, and simulation modes. For descriptions of individual HSPICE commands mentioned in this chapter, see the HSPICE Reference Manual: Commands and Control Options. These topics are discussed in the following sections: ■ Setting Environment Variables ■ Standard Input Files ■ Standard Output Files ■ Working Directory Path Character Limit Setting Environment Variables The following sections describe procedures for setting the environment variables needed to run HSPICE. ■ License Variable ■ License Queuing Variable ■ Temporary Directory Variable ■ Windows Variable License Variable HSPICE or HSPICE RF requires you to set the LM_LICENSE_FILE environment variable. This variable specifies the location of the license.dat HSPICE® User Guide: Simulation and Analysis B-2008.09 11 Chapter 2: Setup Setting Environment Variables license file. Set the LM_LICENSE_FILE environment variable to port@hostname to point to a license file on a server. ■ If you are using the C shell, add the following line to the .cshrc file: setenv LM_LICENSE_FILE port@hostname ■ If you are using the Bash or Bourne shell, add these lines to the .bashrc or .profile file: LM_LICENSE_FILE=port@hostname export LM_LICENSE_FILE The port and host name variables correspond to the TCP port and license server host name specified in the SERVER line of the Synopsys license file. Each license file can contain licenses for many packages from multiple vendors. You can specify multiple license files by separating each entry. For UNIX, use a colon (:) and for Windows, use a semicolon (;). For details about setting license file environment variable, see “Setting Up HSPICE for Each User” in the Installation Guide. Temporary Directory Variable Specify the location to deposit scratch files by setting the tmpdir (UNIX/ Linux), TEMP or TMP (Windows) environment variable. HSPICE opens three scratch files in the /tmp directory. To change this directory, reset the tmpdir environment variable in the HSPICE command script. In the Windows environment, HSPICE opens three scratch files in the c:\<path>\TEMP (or \TMP) directory. To change this directory, reset the TEMP or TMP environment variable in the HSPICE command script. License Queuing Variable The optional META_QUEUE environment variable is a useful feature that causes HSPICE or HSPICE RF to wait for an available license. It is particularly helpful in environments where the tool is run sequentially from batch files and a license checkout failure could result in the loss of important data. (AvanWaves also supports use of this environment variable.) META_QUEUE, however, does not queue across license “pools” (which are disallowed in FLEXlm). Setting the META_QUEUE environment variable to 1 enables HSPICE/HSPICE RF licenses to be queued: setenv META_QUEUE 1 12 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 2: Setup Standard Input Files A pool of licenses is created by an INCREMENT line that contains one or more license tokens. For example: If you have five HSPICE or RF floating licenses and all five licenses are checked out with the META_QUEUE environment variable enabled, then the next job submitted waits in the queue until a license is available (when one of the previous five jobs finishes). When META_QUEUE is enabled and all available licenses are in use, an error message is issued that says no licenses are available. Additional pools can be created by having multiple INCREMENT lines in the same license file, such as exist in the case of separate tool purchases or offmaintenance keys. Another way multiple pools can exist is with the addition of multiple server entries in the LM_LICENSE_FILE variable. For example:LM_LICENSE_FILE = 27000@server1:27000@server2:27000@server3 Without queuing enabled, the tool tries the INCREMENT lines in server1, then server2, and so on, until all servers in the list are exhausted. When you turn on queuing, however, the first INCREMENT in the first pool that is queried (server1) queues the request, and the application does not continue to look in other license pools for available tokens. Windows Variable Setting the HSPWIN_KEY environment variable to 1 checks out the hspicewin license token first when an HSPICE simulation is run. If not set to 1, an hspice token is checked out first. The HSPWIN_KEY environment variable is only available on the Windows platform. Note: When installing the HSPICE program on Windows, the ADMINISTRATOR priority is essential for successful installation. Standard Input Files This section describes the standard input files to HSPICE. Design and File Naming Conventions The design name identifies the circuit and any related files, including: HSPICE® User Guide: Simulation and Analysis B-2008.09 13 Chapter 2: Setup Standard Input Files ■ Schematic and netlist files. ■ Simulator input and output files. ■ Design configuration files. ■ Hardcopy files. HSPICE and AvanWaves extract the design name from their input files, and perform actions based on that name. For example, AvanWaves reads the design.cfg configuration file to restore node setups used in previous AvanWaves runs. You can also use WaveView Analyzer. HSPICE and AvanWaves read and write files related to the current circuit design. Files related to a design usually reside in one directory. The output file is stdout on UNIX platforms, which you can redirect. Table 1 lists input file types, and their standard names. The sections that follow describe these files. Table 1 Input Files Input File Type File Name Output configuration file meta.cfg Initialization file hspice.ini DC operating point initial conditions file design.ic# Input netlist file design.sp Library input file library_name Analog transition data file design.d2a Output Configuration File (meta.cfg) You use the output configuration file to set up the printer, plotter, and terminal. The HSPICE default search order for the meta.cfg file is as follows: 1. cwd/meta.cfg 2. -i input.sp/meta.cfg — same directory as input case 3. \$HOME/meta.cfg — user HOME directory 4. \$installdir/meta.cfg 14 — current working directory — HSPICE installation directory HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 2: Setup Standard Input Files Besides the meta.cfg file, HSPICE also reads one cwd/casename_prefix.cfg configuration file for current simulation case output. The configuration file can contain one line (default_include=\$path>/filename) for HSPICE to read one defaultinclude file. The default-include filename is case-sensitive (except for the Windows versions of HSPICE). The default-include file can be overridden by setting the environment variable 'default_include'(note lower case). Initialization File (hspice.ini) The initialization file enables you to specify user defaults. If HSPICE reads one hspice.ini file, HSPICE includes its contents at the top of the input file. (This does not apply to HSPICE RF). All HSPICE simulations will look for ONE implicit hspice.ini file. The HSPICE default search order for the hspice.ini file is: 1. cwd/hspice.ini —current working directory 2. \$HOME/hspice.ini —user HOME directory 3. \$installdir/hspice.ini —HSPICE installation directory You can use an initialization file to set options (for .OPTION statements) and to access libraries. To include customized initialization files, you can define default_include=filename in a command.inc or meta.cfg file. DC Operating Point Initial Conditions File The DC operating point initial conditions file, <design>.ic#, is an optional input file that contains initial DC conditions for particular nodes. You can use this file to initialize DC conditions, by using either a .NODESET or an .IC statement. A .SAVE statement can also create a <design>.ic# file. A subsequent .LOAD statement initializes the circuit to the DC operating point values specified in this file. Input Netlist File The input netlist file, <design>.sp, contains the design netlist. Optionally, it can also contain statements specifying the type of analysis to run, type of output desired, and what library to use. HSPICE® User Guide: Simulation and Analysis B-2008.09 15 Chapter 2: Setup Standard Output Files Library Input File You use library_name files to identify libraries and macros that need to be included for simulating design.sp. Analog Transition Data File When you run HSPICE in standalone mode, a <design>.d2a file contains state information for a U Element mixed-mode simulation. Standard Output Files This section describes the standard output files from HSPICE. The various types of output files produced are listed in Table 2. For information about the standard output file from HSPICE RF, see HSPICE RF Output File Types in the HSPICE RF Manual. Table 2 HSPICE Output Files and Extensions Output File Type AC analysis measurement results .ma#a AC analysis results (from .POST statement) .ac# DC analysis measurement results .ms# DC analysis results (from .POST statement) .sw# Digital output .a2d FFT analysis graph data (from FFT statement) .ft# Hardcopy graph data (from meta.cfg PRTDEFAULT) .gr#b Operating point information (from .OPTION OPFILE statement) .dp# Operating point node voltages (initial conditions) .ic# Output listing 16 Extension .lis, or user-specified HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 2: Setup Standard Output Files Table 2 HSPICE Output Files and Extensions Output File Type Extension Output status .st# Output tables (from .DCMATCH OUTVAR statement) .dm# Subcircuit cross-listing .pa# Transient analysis measurement results .mt# Transient analysis results (from .POST statement) .tr# Waveform viewing files from .OPTION WDF argument for use with Synopsys WaveView/SX tools *_wdf.tr#, *_wdf.sw#, or *_wdf.ac# a. # can be either a sweep number or a hardcopy file number. For .ac#, .dp#, .dm#, .ic#, .st#, .sw#, and .tr# files, # is from 0 through 9999. b. Requires a .GRAPH statement, or a pointer to a file in the meta.cfg file. The Windows and Linux versions of HSPICE do not generate this file. AC Analysis Results File HSPICE writes AC analysis results to file output_file.ac#, where # is 09999, according to your specifications following the .AC statement. These results list the output variables as a function of frequency. AC Analysis Measurement Results File HSPICE writes AC analysis measurement results to file output_file.ma# when the input file includes a .MEASURE AC statement. DC Analysis Results File HSPICE writes DC analysis results to file output_file.sw#, where # is 09999, when the input file includes a .DC statement. This file contains the results of the applied stepped or swept DC parameters defined in that statement. The results can include noise, distortion, or network analysis. HSPICE® User Guide: Simulation and Analysis B-2008.09 17 Chapter 2: Setup Standard Output Files DC Analysis Measurement Results File HSPICE writes DC analysis measurement results to file output_file.ms# when the input file includes a .MEASURE DC statement. Digital Output File The digital output file, design.a2d, contains data that the A2D conversion option of the U element converted to digital form. FFT Analysis Graph Data File The FFT analysis graph data file, output_file.ft#, contains the graphical data needed to display the FFT analysis waveforms. Hardcopy Graph Data File HSPICE writes hardcopy graph data to file output_file.gr# when the input file includes a .GRAPH statement. The file produced is in the form of a printer file, typically in Adobe PostScript or HP PCL format. This facility is not available in the Windows and Linux versions of HSPICE. Operating Point Information File HSPICE writes operating point information to file design.dp# when the input file includes an .OPTION OPFILE=1 statement. Operating Point Node Voltages File HSPICE writes operating point node voltages to file output_file.ic#, where # is 0 to 9999, when the input file includes a .SAVE statement. These node voltages are the DC operating point initial conditions. 18 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 2: Setup Standard Output Files Output Listing File The output listing is a text file. It can be named <output_file> (no file extension), output_file.lis, or with a file extension that you specify, depending on which format you use to start the simulation. The output file includes the following information: ■ Name of the simulator used. ■ Version of the HSPICE simulator used. ■ Synopsys message block. ■ Input filename. ■ User name. ■ License details. ■ Copy of the input netlist file. ■ Node count. ■ Operating point parameters. ■ Actual control option values that HSPICE uses for the present simulation (useful when options such as RUNLVL override user-set values.) ■ Details of the volt drop, current, and power for each source and subcircuit. ■ Low-resolution ASCII plots, originating from a .PLOT statement. ■ Results of a .PRINT statement. ■ Results of the .OPTION statements. ■ Total CPU time (the sum of op point, transient, readin, errchk, setup, and output times). ■ In the following snippet of a *.lis file, you can see that the total cpu time is the sum of op point, transient, readin, errchk, setup and output analysis times. analysis op point transient readin errchk setup output total cpu time time # points 0.00 1 0.07 446328 0.01 0.01 0.00 0.00 0.09 seconds HSPICE® User Guide: Simulation and Analysis B-2008.09 tot. iter 4 64 conv.iter 32 rev= 3 19 Chapter 2: Setup Standard Output Files The different analyses stand for time required to: • Op point: Do operating point analysis. • Transient: Do transient analysis. • Readin: Read the user data file and any additional library files, and generate an internal representation of the information. • Errchk: Check the errors and evaluate the models. • Output: Prepare the output files and to process all prints and plots. • Setup: Construct a sparse matrix pointer system. • Total CPU time is the time taken for the simulation only. It will differ slightly from run to run, even though runs are identical. It will not include memory/disk allocation time or disk I/O time. You can calculate this by subtracting job ended time from job started time. Output Status File The output status file, output_file.st#, where # is 0-9999, contains the following runtime reports: ■ Start and end times for each CPU phase. ■ Options settings, with warnings for obsolete options. ■ Status of preprocessing checks for licensing, input syntax, models, and circuit topology. ■ Convergence strategies that HSPICE uses on difficult circuits. You can use the information in this file to diagnose problems, particularly when communicating with Synopsys Customer Support. Output Tables The .DCMATCH output tables file, output_file.dm#, contains the variability data from analysis. 20 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 2: Setup Working Directory Path Character Limit Subcircuit Cross-Listing File If the input netlist includes subcircuits, HSPICE automatically generates a subcircuit cross-listing file, output_file.pa#, where # is 0-9999. This file relates the subcircuit node names, in the subcircuit call, to the node names used in the corresponding subcircuit definitions. In HSPICE RF, you cannot replicate output commands within subcircuit (subckt) definitions. Transient Analysis Measurement Results File HSPICE writes transient analysis measurement results to file output_file.mt# when the input file includes an .MEASURE TRAN statement. Transient Analysis Results File Both HSPICE and HSPICE RF place the results of transient analysis in file output_file.tr#, where # is 0-9999, as set forth in the -n command-line argument. This file lists the numerical results of transient analysis. A .TRAN statement in the input file, together with an .OPTION POST statement, creates this post-analysis file. If the input file includes an .OPTION POST statement, then the output file contains simulation output suitable for a waveform display tool. Waveform Viewing File Following use of .OPTION WDF for transient, DC, or AC analyses, for the WDF waveform file, HSPICE automatically appends _wdf into the output file root name to specify that it is in WDF format. The file names appear as: *_wdf.tr#, *_wdf.sw#, or *_wdf.ac#. For example, the WDF waveform output file will be named: design_wdf.tr0. Working Directory Path Character Limit HSPICE has a limitation on the number of characters in a working directory path. HSPICE accepts a working directory path of less than 236 characters. HSPICE® User Guide: Simulation and Analysis B-2008.09 21 Chapter 2: Setup Working Directory Path Character Limit Paths of greater length result in HSPICE exiting with a signal 11 error. To check the length of the working directory path, you can use the UNIX command: % pwd | wc -c 22 HSPICE® User Guide: Simulation and Analysis B-2008.09 3 3 Startup and Simulation Describes the invocation commands, and simulation modes. For descriptions of individual HSPICE commands mentioned in this chapter, see the HSPICE Reference Manual: Commands and Control Options. These topics are discussed in the following sections: ■ Running HSPICE Simulations ■ Running HSPICE RF Simulations ■ Running Multithreading or Multiprocessing HSPICE Simulations ■ Running HSPICE Interactively ■ Using HSPICE in Client/Server Mode ■ Running HSPICE to Calculate New Measurements Running HSPICE Simulations Use the following syntax to start HSPICE: hspice [-i path/input_file] [-o path/output_file] [-n number] [-html path/html_file] [-d] [-C path/input_file] [-CC path/input_file] [-I] [-K] [-L command_file] [-S] [-mp [number]] [-mt number] [-meas measure_file] [-top subcktname] [-hdl filename] [-hdlpath pathname] [-vamodel name] [-vamodel name2...] [-help] [-doc] [-h] [-v] [-x] For a description of the hspice command syntax and arguments, see “HSPICE Command Syntax” in the HSPICE Reference Manual: Commands and Control Options. HSPICE® User Guide: Simulation and Analysis B-2008.09 23 Chapter 3: Startup and Simulation Running HSPICE Simulations When you invoke an HSPICE simulation, the following sequence of events occurs: 1. Invocation. For example, at the shell prompt, enter: hspice demo.sp > demo.out & This command invokes the UNIX hspice shell command on input netlist file demo.sp and directs the output listing to file demo.out. The “&” character at the end of the command invokes HSPICE in the background, so that you can continue to use the window and keyboard while HSPICE runs. 2. Script execution. The hspice shell command starts the HSPICE executable from the appropriate architecture (machine type) directory. The UNIX run script launches a HSPICE simulation. This procedure establishes the environment for the HSPICE executable. The script prompts for information, such as the platform that you are using, and the version of HSPICE to run. (Available versions are determined when you install HSPICE.) 3. Licensing. HSPICE supports the FLEXlm licensing management system. When you use FLEXlm licensing, HSPICE reads the LM_LICENSE_FILE environment variable to find the location of the license.dat file. If HSPICE cannot authorize access, the job terminates at this point, and prints an error message in the output listing file. 4. Simulation configuration. HSPICE reads the appropriate meta.cfg file. The search order for the configuration file is the user login directory, and then the product installation directory. 5. Design input. HSPICE opens the input netlist file demo.sp. If this file does not exist, a no input data error appears in the output listing file. (UNIX/Linux) HSPICE opens three scratch files in the /tmp directory. To change this directory, reset the tmpdir environment variable in the HSPICE command script. (Windows) HSPICE opens three scratch files in the c:\<path>\TEMP (or \TMP) directory. To change this directory, reset the TEMP or TMP environment variable in the HSPICE command script. 24 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 3: Startup and Simulation Running HSPICE Simulations HSPICE opens the output listing file demo.out for writing. If you do not own the current directory, HSPICE terminates with a file open error. The following is an example of a simple HSPICE input netlist: *Inverter Circuit .OPTION LIST NODE POST .TRAN 200P 20N SWEEP TEMP -55 75 10 .PRINT TRAN V(IN) V(OUT) M1 VCC IN OUT VCC PCH L=1U W=20U M2 OUT IN 0 0 NCH L=1U W=20U VCC VCC 0 5 VIN IN 0 0 PULSE .2 4.8 2N 1N 1N 5N 20N CLOAD OUT 0 .75P .MODEL PCH PMOS .MODEL NCH NMOS .ALTER CLOAD OUT 0 1.5P .END 6. Library input. HSPICE reads any files that you specified in .INCLUDE and .LIB statements. 7. Operating point initialization. HSPICE reads any initial conditions that you specified in .IC and .NODESET statements, finds an operating point (that you can save with a .SAVE statement), and writes any operating point information that you requested. 8. Analysis. HSPICE can perform a single or multipoint sweep of the design and produce one set of output files. In the example above, the .TRAN statement causes HSPICE to perform a multipoint transient sweep analysis for 20ns for temperatures ranging from -55° C to 75° C, in steps of 10° C. 9. Worst-case .ALTER. You can vary simulation conditions, and repeat the specified single or multipoint analysis. The above example changes CLOAD from 0.75 pF to 1.5 pF, and repeats the multipoint transient analysis. You can activate multiprocessing while running .ALTER cases by entering hspice -mp on the command line. 10. Suspending a simulation HSPICE® User Guide: Simulation and Analysis B-2008.09 25 Chapter 3: Startup and Simulation Running HSPICE Simulations on Windows Suspend a simulation job by pressing Ctrl-Z. The load sharing facility (LSF) frees up the license for another simulation job. To resume the job, on the same terminal, type either fg or bgto access a license and continue the simulation. 11. Normal termination. After you complete the simulation, HSPICE closes all files it opened and releases all license tokens. Running HSPICE Simulations on Windows You can use the MS-DOS command window to run HSPICE in command line mode, similar to UNIX/Linux. For example: 1. Open an MS-DOS command window (Run > cmd). 2. Enter your case directory. 3. Type the following to invoke HSPICE and view command line help: c:\synopsys\Hspice_release_version\bin\hspice 4. Or type the following command to run a simulation: C:\synopsys\Hspice_release_version\bin\hspice filename.sp -o Running HSPICE RF Simulations Use the following syntax to invoke HSPICE RF: hspicerf [-a] inputfile [outputfile] [-h] [-v] For a description of the hspicerf command syntax and arguments, see “HSPICE RF Command Syntax” in the HSPICE Reference Manual: Commands and Control Options. 26 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 3: Startup and Simulation Running HSPICE Interactively Running HSPICE Interactively For a full discussion, refer to Chapter 5, Using Interactive Mode. Interactive mode enables you to use these HSPICE commands at the HSPICE prompt to help you simulate circuits interactively: ac [...statement] cd dc [...statement] edit help info outflag input list [lineno] load filename ls [directory] measure [statement] op print <tran/ac/dc>,v/vm/vr/vi/vp/vdb> pwd quit run save netlist/command filename set outflag true | false tran [...statement] Starting Interactive Mode To invoke the interactive mode, enter: hspice -I You can also use the help command at the HSPICE prompt for an annotated list of the commands supported in the interactive mode. The interactive mode also supports saving commands into a script file. To save the commands that you use and replay them later, enter: hspice> save command filename Running a Command File in Interactive Mode To run the command you have saved in a command file, enter: hspice> -I -L filename HSPICE® User Guide: Simulation and Analysis B-2008.09 27 Chapter 3: Startup and Simulation Running Multithreading or Multiprocessing HSPICE Simulations Quitting Interactive Mode To exit the interactive mode and return to the system prompt, enter: hspice> quit Running Multithreading or Multiprocessing HSPICE Simulations HSPICE simulations include device model evaluations and matrix solutions. You can run model evaluations concurrently on multiple CPUs by using multithreading to significantly improve simulation performance. Model evaluation takes most of the time. To determine how much time HSPICE spends evaluating models and solving matrices, specify .OPTION ACCT=2 in the netlist. By using multithreading, you can speed up simulations with no loss of accuracy. Multithreading gives the best results for circuit designs that contain many voltage- and current-controlled sources such as: VCCS(G), VCVS(E), CCCS(F), CCVS(H), and MOSFET, diode, or BJT models in the netlist. The requirements for when HSPICE can use more than 1 thread are: ■ 512 behavioral elements (VCCSs, VCVSs, CCCSs, CCVSs) ■ 512 transistor devices (MOSFETs, BJTs) ■ 1024 diodes If the circuit lacks the required number of active devices, HSPICE automatically uses a single thread. To reduce the threshold number of devices, you can use .OPTION MTTHRESH to set the number of active devices. MTTHRESH must = 2 or more. Otherwise, HSPICE MT defaults to 512. Note: In the case of too few active devices, a multithreaded simulation may run slower than single-threaded. Whether or not performance degrades depends on many facets of the circuit topology. The default threshold of 512 can be lowered in case the circuit under simulation has less than 512 active elements and still accelerates well with multithreading. To Run Multithreading One license is required per two CPUs. To run multithreading on the UNIX/Linux platforms, enter: 28 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 3: Startup and Simulation Running Multithreading or Multiprocessing HSPICE Simulations % hspice -mt number -i input_file -o output_file ■ Omitting the number parameter results in an error message. ■ If you specify a number larger than the number of available CPUs, HSPICE sets the number of threads equal to the number of available CPUs. For additional information about command-line options, see “HSPICE Command Syntax” in the HSPICE Reference Manual: Commands and Control Options. In Windows NT Explorer: 1. Click Start > Run, type cmd, then press Enter. 2. In the cmd.exe window, cd to the case directory. 3. Type: hspice.exe -mt number -i input_file -o output_file In the Synopsys HSPICE User Interface (HSPUI): 1. Select the correct hspice.exe version in the Version combo box. 2. Select MultiCpu Option and select the mt number. 3. Select the input case and run. Performance Improvement Estimations Tmt=Tserial + Tparallel/Ncpu + Toverhead Where: Tserial represents HSPICE calculations that are not threaded. Tparallel represents threaded HSPICE calculations. Ncpu is the number of CPUs used. Toverhead is the overhead from multithreading. Typically, this represents a small fraction of the total runtime. For example, for a 151-stage NAND ring oscillator using LEVEL 49, Tparallel is about 80% of T1cpu (the CPU time associated with a single CPU) if you run with two threads on a multi-CPU machine. Ideally, assuming Toverhead=0, you can achieve a speedup of: T1cpu/(0.2T1cpu + 0.8T1cpu/2cpus)=1.67 The typical Tparallel value is 0.6 to 0.7 for moderate-to-large circuits. HSPICE® User Guide: Simulation and Analysis B-2008.09 29 Chapter 3: Startup and Simulation Running Multithreading or Multiprocessing HSPICE Simulations Multiprocessing .ALTER Cases, Transient Sweeps, Monte Carlo While multithreading (-mt) is suitable for netlists with huge numbers of active elements (MOSFETs, BJTs or diodes), if you specify the -mp number (multiprocessing) switch, then HSPICE can also take advantage of multiple cores and processors for simulations containing .ALTER cases, transient sweeps, and Monte Carlo analyses. Here Monte Carlo analysis includes DC and transient. You can limit the number of CPUs by specifying the number. If the number is not specified, then HSPICE auto-determines the child processes by the number of available CPUs. This information is printed to the .st0 file. .ALTER Cases In .ALTER cases, MP works by creating (forking) child HSPICE processes for each ALTER case up to the number of processors. Each of these HSPICE child processes checks out a license. Additional ALTER cases are divided among the HSPICE processes and run in a serial fashion. For example: If you start a simulation with a main case and 11 ALTER cases on a 4-CPU system, for example, HSPICE will fork four child processes and divide the main case and ALTER cases among the 4 CPUs, which are then performed serially. The number of available processors and cores can be determined by examining the processor, physical ID, and core ID flags in the /proc/cpuinfo file. HSPICE waits for all the cases to be run then combines the resulting listing files together. TR0, IC0, PA0, MT0 and other files that are normally generated, one for each ALTER, will still remain separate. The wall clock time of a multiprocess .alter analysis is printed in the .lis file. For example: ****** Runtime Statistics for Alter Analysis with MP total elapsed time 13 seconds job started at 17:21:59 05/16/2008 job ended at 17:22:12 05/16/2008 ****** Note: Elapsed time may differ slightly from the total elapsed time of all child processes due to the overhead time cost of output merging. Known Limitation The -mp feature only operates with .alter commands in the top netlist; it does not operate with .alters embedded in .include files. 30 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 3: Startup and Simulation Using HSPICE in Client/Server Mode Transient Sweeps and Monte Carlo Trials In transient sweep and Monte Carlo analyses, MP works by creating (forking) child HSPICE processes for multiple jobs based on the partition of a sweep or Monte Carlo loop. Each of these HSPICE processes checks out a license. For example: If you start a simulation with 100 trials of transient Monte Carlo on a 4-CPU system. HSPICE forks four child processes and divides the 100 trials among the 4 CPUs, so each child process runs 25 trials. Since one license is checked out at the beginning of the simulation, three additional licenses are checked out and the related information is printed in the .lis file. Multiprocessing Notes When using –mp, note that: ■ Unlike –mt, the –mp option is not available on the Windows platform. ■ MP only works on single systems with multiple physical processors and does not distribute jobs across the LAN. ■ HSPICE MP will only assign one job to each processor at a time. ■ MP takes advantage of multiple processor cores. Note: Using MP with MT and Client/Server mode: If both -mp and -mt are used, then -mp takes over and -mt is ignored. If both -mp and -CC are used, then -CC takes over and -mp is ignored. See Launching the Advanced Client/Server (C/S) Mode. Using HSPICE in Client/Server Mode When you run many small simulation cases, you can use the client/server mode to improve performance. This performance improvement occurs because you check out and check in an HSPICE license only once. This is an effective measure when you characterize cells. (For an advanced procedure see Launching the Advanced Client/Server (C/S) Mode.) HSPICE® User Guide: Simulation and Analysis B-2008.09 31 Chapter 3: Startup and Simulation Using HSPICE in Client/Server Mode To Start Client/Server Mode Starting the client/server mode creates an HSPICE server and checks out an HSPICE license. To start the client/server mode, enter: hspice> -C Server The server name is a specific name connected with the machine on which HSPICE runs. When you create the server, HSPICE also generates a hidden .hspicecc directory in your home directory. HSPICE places some related files in this directory, and removes them when the server exits. HSPICE Client/Server mode does not let one user create several servers on the same machine. When you create a server, the output on the screen is: *************************************** *Starting HSPICE Client/Server Mode...* *************************************** Checking out HSPICE license... HSPICE license has been checked out. *********************************************** *Welcome to HSPICE Client/Server Mode!* ******************************************* After you create the server, it automatically runs in the background. If the server does not receive any request from a client for 12 hours, the server releases the license, and exits automatically. Client The client can send a request to the server to ask whether an HSPICE license has been checked out, or to kill the server. ■ If the request is to check the license status, the server checks whether an HSPICE license has been checked out, and replies to the client. The syntax of this request is: hspice -C casename.sp Where casename is the name of the circuit design to simulate. 32 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 3: Startup and Simulation Using HSPICE in Client/Server Mode ■ If the client receives ok, it begins to simulate the circuit design. ■ If the client receives no, it exits. ■ If the server receives several requests at the same time, it queues these requests, and process them in the order that the server received them. ■ If HSPICE does not find a server, it creates a server first. Then the server checks out an HSPICE license, and simulates the circuit. ■ If the request is to kill the server, the server releases the HSPICE license and other sources, and exits. When you kill the server, any simulation cases that are queued on that server do not run, and the server's name disappears from the hidden .hspicecc directory in your home directory. If you do not specify an output file, HSPICE directs output to the client terminal. Use the following syntax to redirect the output to a file, instead of to the terminal: hspice -C casename.sp > <output_file> To Simulate a Netlist in Client/Server Mode Once you have started the client/server mode, which automatically checks out an HSPICE license, you can run simulations. To simulate a netlist in client/server mode, enter: hspice -C path/input_file Note: This mode also supports other HSPICE command line options. For a description of the options shown, see “HSPICE Command Syntax” in the HSPICE Reference Manual: Commands and Control Options. To Quit Client/Server Mode Quitting the client/server mode releases the HSPICE license and exits HSPICE. To exit the client/server mode, enter: hspice -C -K HSPICE® User Guide: Simulation and Analysis B-2008.09 33 Chapter 3: Startup and Simulation Using HSPICE in Client/Server Mode Launching the Advanced Client/Server (C/S) Mode The Advanced Client/Server Mode provides an efficient interface for cell characterization applications. The advanced C/S mode facilitates the Client/Server mode as follows: ■ Checks out an HSPICE license once and locks it to do multiple simulations in sequence. ■ Reads in the common file only once in multiple simulations with different circuits, when they include a common file, which may a contain subcircuit or model definition. ■ Provides an easy-to-use interface. Command Syntax Three commands start the HSPICE server, do simulations, and stop the server. The following tables describe the arguments. 1. To start the server, enter: hspice -CC [-port hostname:port_num] [-share inc_file] + [-stop stop_time] 2. To begin a simulation, enter: hspice -CC input_file [-port hostname:port_num] [-o output_file] 3. To stop the HSPICE server, enter: hspice -CC -K [-port hostname:port_num] Argument Description -CC Launches the advanced HSPICE C/S mode. After the server starts, it will run in background. -port hostname: port_num Starts server on the designated port hostname:port_num. If you do not specify this argument, the default port number (25001) is used. If the default port is not available, HSPICE chooses any free port. When you start the server or run a case with -port hostname:port_num, the hostname will be ignored. But you can stop the server with -port hostname:portnum to implement remote control. HSPICE will print out port information to the screen. 34 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 3: Startup and Simulation Using HSPICE in Client/Server Mode Argument Description -share inc_file Specifies a common file name shared by different circuits. -stop stop_time If you do not specify a “stop_time” the server will stop automatically after the default stop_time of 12 hours. The maximum “stop_time” that can be specified is 12 hours. -o output_file Specifies the output file name. If an “output_file” is not specified, HSPICE uses the input root filename as the output file root filename. -K Shuts down the client server. Application Instances In the following instances, assume there are 5 netlist files (t1.sp, t2.sp, … t5.sp) to be run, and this group includes a common file. Also assume that all 5 files are located in the same directory: /home1/user1/test/testcase. t1.sp V1 1 0 dc 1.05 V2 2 0 dc 0 .temp 125 .inc "/home1/user1/test/model/model_file" .inc "101.spc" .end t2.sp V1 1 0 dc 1.05 V2 2 0 dc 0 .temp 125 .inc "/home1/user1/test/model/model_file" .inc "102.spc" .end ... t5.sp V1 1 0 dc 1.05 V2 2 0 dc 0 .temp 125 .inc "/home1/user1/test/model/model_file" .inc "105.spc" .end HSPICE® User Guide: Simulation and Analysis B-2008.09 35 Chapter 3: Startup and Simulation Using HSPICE in Client/Server Mode Using the following commands, you can invoke the HSPICE C/S mode to run this group of cases. The work path is: /home1/user1/test/testcase 1. Start the HSPICE server on the default port and read in the common file: hspice -CC -share /home1/user1/test/model/model_file 2. Run a simulation on the default port without reading in the common file again. hspice -CC t1.sp Explanation: Since the .inc "/home1/user1/test/model/model_file" statement appears in each netlist, it is not read in again because the server has already processed the information. 3. Repeat Step 2 until all cases are simulated. 4. Exit the HSPICE Client/Server mode. hspice -CC -K The sequence of commands is: hspice hspice hspice hspice hspice hspice hspice -CC -CC -CC -CC -CC -CC -CC -share t1.sp t2.sp t3.sp t4.sp t5.sp -K /home1/user1/test/model/model_file Notes ■ If you start the server and run simulations by Perl script, use the system (\$cmd) instead of '\$cmd' to avoid hanging the server. For example, #!/depot/perl-5.8.3/bin/perl -w ... \$cmd = "hspice -CC -share inc_file "; ... ■ 36 To use multiple servers, you need to specify multiple ports. If you submit several scripts to start multiple servers, you need to specify multiple ports. If you do not designate port numbers to a multiple-cpu machine or to a machine in computer farm environment, only one server will start on the default port number. If the default port is not available, HSPICE chooses any free port. HSPICE also prints out port information. The printed message is similar to "Server is started on port=port_num".To assure that HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 3: Startup and Simulation Using HSPICE in Client/Server Mode the simulation is run successfully in a different script, add -port port_num. For example, #!/depot/perl-5.8.3/bin/perl -w ##start server without designated port, redirect output #information \$cmd = "hspice -CC >& log "; system(\$cmd) ; ##get the port_num on which server is started \$portnum=`grep port= log|awk {{print \$6}}`; ##do simulation \$cmd1 = "hspice -CC test1.sp -port \$portnum"; system(\$cmd1) ; ... ##stop server \$cmdn ="hspice -CC -K -port \$portnum"; system(\$cmdn) ; ■ To avoid redefinition errors, verify that the common file both in “-share inc_file” and in “.inc inc_file” of every netlist has the same absolute path and file name. For example, there are 5 netlist files, t1.sp, t2.sp, t3.sp, t4.sp, and t5.sp to be run and this group of netlists includes a common file. Assume that all these 5 files are in the same directory /home1/user1/test/testcase. The following is the correct usage. hspice hspice hspice hspice hspice hspice hspice -CC -CC -CC -CC -CC -CC -CC -share /home1/user1/test/model/model_file t1.sp t2.sp t3.sp t4.sp t5.sp -K Each of the netlists includes .inc "/home1/tom/test/model/model_file" In every case, the absolute path name of the common file in .inc "/home1/user1/test/model/model_file" is the same as the absolute path name of the common file specified by -share /home1/user1/test/model/model_file. The common file /home1/user1/test/model/model_file will only be read in once and .inc "/home1/user1/test/model/model_file" will be ignored in every case. HSPICE® User Guide: Simulation and Analysis B-2008.09 37 Chapter 3: Startup and Simulation Running HSPICE to Calculate New Measurements Running HSPICE to Calculate New Measurements When you want to calculate new measurements from previous simulation results produced by HSPICE, you can rerun HSPICE. To Calculate New Measurements To get new measurements from a previous simulation, enter: hspice -meas measure_file -i wavefile [-o outputfile] For a description of the options shown, see HSPICE Command Syntax in the HSPICE Reference Manual: Commands and Control Options. 38 HSPICE® User Guide: Simulation and Analysis B-2008.09 4 4 Input Netlist and Data Entry Describes the input netlist file and methods of entering data. For descriptions of individual HSPICE commands referenced in this chapter, see Chapter 2, HSPICE and HSPICE RF Netlist Commands, in the HSPICE Reference Manual: Commands and Control Options. The following topics are discussed in this chapter: ■ Input Netlist File Guidelines ■ Input Netlist File Composition ■ Using Subcircuits ■ Subcircuit Call Statement Discrete Device Libraries ■ Post-Layout Back-Annotation Input Netlist File Guidelines HSPICE and HSPICE RF operate on an input netlist file, and store results in either an output listing file or a graph data file. An input file, with the name <design>.sp, contains the following: ■ Design netlist (subcircuits, macros, power supplies, and so on). ■ Statement naming the library to use (optional). ■ Specifies the type of analysis to run (optional). ■ Specifies the type of output desired (optional). An input filename can be up to 1024 characters long. The input netlist file cannot be in a packed or compressed format. To generate input netlist and library input files, HSPICE or HSPICE RF uses either a schematic netlister or a text editor. HSPICE® User Guide: Simulation and Analysis B-2008.09 39 Chapter 4: Input Netlist and Data Entry Input Netlist File Guidelines Statements in the input netlist file can be in any order, except that the first line is a title line. In HSPICE, the last .ALTER submodule must appear at the end of the file and before the .END statement. Note: If you do not place an .END statement at the end of the input netlist file, HSPICE or HSPICE RF issues an error message. Netlist input processing is case insensitive, except for file names and their paths. HSPICE and HSPICE RF do not limit the identifier length, line length, or file size. Input Line Format ■ The input reader can accept an input token, such as: • a statement name • a node name • a parameter name or value Any valid string of characters between two token delimiters is a token. You can use a character string as a parameter value in HSPICE, but not in HSPICE RF. See Delimiters on page 46. ■ An input statement, or equation can be up to 1024 characters long. ■ HSPICE or HSPICE RF ignores differences between upper and lower case in input lines, except in quoted filenames. ■ To continue a statement on the next line, enter a plus (+) sign as the first non-numeric, non-blank character in the next line. ■ To indicate “to the power of” in your netlist, use two asterisks (**). For example, 2**5 represents two to the fifth power (25). ■ To continue all HSPICE or HSPICE RF statements, including quoted strings (such as paths and algebraics), use a single whitespace followed by a backslash ( \) or a double backslash ( \\) at the end of the line that you want to continue. • ■ A single backslash preserves white space. All characters after the listed statement lines will be ignored: • • 40 .include 'filename' .lib 'filename' corner HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 4: Input Netlist and Data Entry Input Netlist File Guidelines • .enddata, .end, .endl, .ends and .eom For example: .include 'biasckt.inc'; .lib 'mos25l.l' tt, ■ \$ semicolon ignored \$ comma ignored Parameter names must begin with an alphabetic character, but thereafter can contain numbers and some special characters. See Special Characters. • When you use an asterisk (*) or a question mark (?) with a .PRINT, .PROBE, .LPRINT (HSPICE RF), or .CHECK (HSPICE RF) statement, HSPICE or HSPICE RF uses the character as a wildcard. For additional information, see Using Wildcards on Node Names on page 61. • When you use curly braces ( { } ), HSPICE converts them to square brackets ( [ ] ) automatically. • Names are input tokens. Token delimiters must precede and follow names. See Delimiters. • Names can be up to 1024 characters long and are not case-sensitive. • Do not use any of the time keywords as a parameter name or node name in your netlist. • The following symbols are reserved operator keywords: () = " ‘ Do not use these symbols as part of any parameter or node name that you define. Using any of these reserved operator keywords as names causes a syntax error, and HSPICE or HSPICE RF stops immediately. Special Characters The following table lists the special characters that can be used as part of node names, element parameter names, and element instance names. For detailed discussion, see the appropriate sections in this chapter. HSPICE® User Guide: Simulation and Analysis B-2008.09 41 Chapter 4: Input Netlist and Data Entry Input Netlist File Guidelines Note: To avoid unexpected results or error messages, do not use the following mathematical characters in a parameter name in HSPICE: * - + ^ and /. Table 3 HSPICE/ HSPICE RF Netlist Special Characters Special Character Node Name Instance Name (cannot be the first character; element key letter only) Parameter Name Delimiters (cannot be the first character, element key letter only) HSPICE P , Included only for HSPICE RF Included only Included only n/a Note: P = character is legal anywhere in the string, first or included ~ tilde ! exclamation point P Included only Included only n/a @ at sign P included only Included only n/a # pound sign P Included only Included only n/a \$ dollar sign Included only Included only (avoid if after a number in node name) Included only In-line comment character % percent HSPICE P , Included only for HSPICE RF Included only HSPICE: included n/a only, Illegal in HSPICE RF ^ caret HSPICE P , included only for HSPICE RF Included only HSPICE: included only (avoid usage), Illegal in HSPICE RF “To the power of”, i.e., 2^5, two raised to the fifth power & ampersand HSPICE P , Included only for HSPICE RF Included only Included only n/a 42 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 4: Input Netlist and Data Entry Input Netlist File Guidelines Table 3 HSPICE/ HSPICE RF Netlist Special Characters Special Character Node Name Note: P = character is legal anywhere in the string, first or included * Instance Name (cannot be the first character; element key letter only) Parameter Name Delimiters (cannot be the first character, element key letter only) asterisk HSPICE: Included only included only (avoid using * in node names), Illegal for HSPICE RF HSPICE: included only (avoid using in parameter names), Illegal in HSPICE RF Comment in both HSPICE/HSPICE RF. Wildcard character. Double asterisk (**) is “To the power of”. () parentheses Illegal Illegal Illegal Token delimiter - minus HSPICE: included only Included only Included only (avoid usage) n/a Included only Included only n/a Included only HSPICE: included only (avoid usage); Illegal in HSPICE RF Continues previous line, except for quoted strings (expressions, paths, algebraics) Illegal optional in Token delimiter HSPICE RF P _ underscore + plus sign P HSPICE: included only HSPICE RF P = equals Illegal .PARAM statements <> less/more than HSPICE P, included only for HSPICE RF Included only Included only n/a ? question mark HSPICE P, Illegal for HSPICE RF Included only Included only Wildcard in character in both HSPICE and HSPICE RF Included only Illegal n/a / forward slash P HSPICE® User Guide: Simulation and Analysis B-2008.09 43 Chapter 4: Input Netlist and Data Entry Input Netlist File Guidelines Table 3 HSPICE/ HSPICE RF Netlist Special Characters Special Character Node Name Note: P = character is legal anywhere in the string, first or included Instance Name (cannot be the first character; element key letter only) Parameter Name Delimiters (cannot be the first character, element key letter only) {} curly braces HSPICE: Included only included only, converts { } to [ ] No conversion for HSPICE RF Included only Auto-converts to square brackets () Single ( { ) or ( } ) can be used in Variation Blocks square brackets Included only Included only Included only n/a \ backslash (requires a whitespace before to use as a continuation) HSPICE: included only, Included only Illegal in HSPICE, Continuation Included only in character for HSPICE RF quoted strings (preserves whitespace) double backslash (requires a whitespace before to use as a continuation) HSPICE: included only, Illegal Illegal Continuation character for quoted strings (preserves whitespace) | pipe HSPICE P, Included only, HSPICE RF Included only Included only n/a , comma Illegal Illegal Illegal Token delimiter period Illegal Included only Included only Netlist keyword, (i.e., .TRAN, .DC, etc.). Hierarchy delimiter when used in node names \\ . 44 HSPICE RF P HSPICE RF P HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 4: Input Netlist and Data Entry Input Netlist File Guidelines Table 3 HSPICE/ HSPICE RF Netlist Special Characters Special Character Node Name Instance Name (cannot be the first character; element key letter only) Parameter Name Delimiters (cannot be the first character, element key letter only) colon Included only Included only Included only Delimiter for element attributes semi-colon Included only Included only Included only n/a Note: P = character is legal anywhere in the string, first or included : ; "" double-quotes Illegal Illegal Illegal Expression and filename delimiter ‘’ single quotes Illegal Illegal Illegal Expression and filename delimiter Blank (whitespace) Use before \ or \\ line continuations Tab Token delimiter Tab Token delimiter First Character The first character in every line specifies how HSPICE and HSPICE RF interprets the remaining line. Table 4 lists and describes the valid characters. Table 4 First Character Descriptions Line If the First Character is... Indicates First line of a netlist Any character Title or comment line. The first line of an included file is a normal line and not a comment. Subsequent lines of netlist, and all lines of included files . (period) Netlist keyword. For example, HSPICE® User Guide: Simulation and Analysis B-2008.09 .TRAN 0.5ns 20ns 45 Chapter 4: Input Netlist and Data Entry Input Netlist File Guidelines Table 4 First Character Descriptions (Continued) Line If the First Character is... Indicates c, C, d, D, e, E, f, F, g, G, h, H, i, I, j, J, k, K, l, L, m, M, q, Q, r, R, s, S, v, V,w,W Element instantiation * (asterisk) Comment line + (plus) Continues previous line Delimiters ■ An input token is any item in the input file that HSPICE or HSPICE RF recognizes. Input token delimiters are: tab, blank (whitespace), comma (,), equal sign (=), and parentheses ( ). ■ Single (‘) or double quotes (“) delimit expressions and filenames. ■ Colons (:) delimit element attributes (for example, M1:VGS). ■ Periods (.) indicate hierarchy. For example, X1.X2.n1 is the n1 node on the X2 subcircuit of the X1 circuit. Instance Names The names of element instances begin with the element key letter (see Table 5), except in subcircuits where instance names begin with X. (Subcircuits are sometimes called macros or modules.) Instance names can be up to 1024 characters long. In HSPICE, the .OPTION LENNAM defines the length of names in printouts (default=16). Table 5 Element Identifiers Letter (First Char) Example Line B IBIS buffer b_io_0 nd_pu0 nd_pd0 nd_out nd_in0 nd_en0 nd_outofin0 nd_pc0 nd_gc0 C 46 Element Capacitor Cbypass 1 0 10pf HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 4: Input Netlist and Data Entry Input Netlist File Guidelines Table 5 Element Identifiers (Continued) Letter (First Char) Element Example Line D Diode D7 3 9 D1 E Voltage-controlled voltage source Ea 1 2 3 4 K F Current-controlled current source Fsub n1 n2 vin 2.0 G Voltage-controlled current source G12 4 0 3 0 10 H Current-controlled voltage source H3 4 5 Vout 2.0 I Current source I A 2 6 1e-6 J JFET or MESFET J1 7 2 3 GAASFET K Linear mutual inductor (general form) K1 L1 L2 1 L Linear inductor LX a b 1e-9 M MOS transistor M834 1 2 3 4 N1 P Port P1 in gnd port=1 z0=50 Q Bipolar transistor Q5 3 6 7 8 pnp1 R Resistor R10 21 10 1000 S S parameter element S1 nd1 nd2 s_model2 V Voltage source V1 8 0 5 T,U,W Transmission Line W1 in1 0 out1 0 N=1 L=1 X Subcircuit call X1 2 4 17 31 MULTI WN=100 LN=5 HSPICE® User Guide: Simulation and Analysis B-2008.09 47 Chapter 4: Input Netlist and Data Entry Input Netlist File Guidelines Hierarchy Paths ■ A period (.) indicates path hierarchy. ■ Paths can be up to 1024 characters long. ■ Path numbers compress the hierarchy for post-processing and listing files. ■ You can find path number cross references in the listing and in the <design>.pa0 file. ■ The .OPTION PATHNUM controls whether the list files show full path names or path numbers. Numbers You can enter numbers as integer, floating point, floating point with an integer exponent, or integer or floating point with one of the scale factors listed in Table 6. Table 6 Scale Factors Scale Factor Symbol Multiplying Factor T tera T 1e+12 G giga G 1e+9 MEG or X mega M 1e+6 K kilo k 1e+3 MIL n/a none 25.4e-6 M milli m 1e-3 U micro μ 1e-6 N nano n 1e-9 P pico p 1e-12 F femto f 1e-15 A 48 Prefix atto a 1e-18 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 4: Input Netlist and Data Entry Input Netlist File Guidelines Note: Scale factor A is not a scale factor in a character string that contains amps. For example, HSPICE interprets the 20amps string as 20e-18mps (2018 amps), but it correctly interprets 20amps as 20 amperes of current, not as 20e-18mps (20-18amps). ■ Numbers can use exponential format or engineering key letter format, but not both (1e-12 or 1p, but not 1e-6u). ■ To designate exponents, use D or E. ■ The .OPTION EXPMAX limits the exponent size. ■ Trailing alphabetic characters are interpreted as units comments. ■ Units comments are not checked. ■ The .OPTION INGOLD controls the format of numbers in printouts. ■ The .OPTION NUMDGT=x controls the listing printout accuracy. ■ The .OPTION MEASDGT=x controls the measure file printout accuracy. ■ In HSPICE, .OPTION VFLOOR=x specifies the smallest voltage for which the value is printed. Smaller voltages print as 0. Parameters and Expressions ■ Parameter names in HSPICE or HSPICE RF use HSPICE name syntax rules, except that names must begin with an alphabetic character. The other characters must be either a number, or a special character. See Table 3 on page 42 in the Special Characters section for a listing of legal parameter names. For example, a “%” is legal if included in HSPICE, but illegal in HSPICE RF. ■ To define parameter hierarchy overrides and defaults, use the .OPTION PARHIER=global | local statement. ■ If you create multiple definitions for the same parameter or option, HSPICE or HSPICE RF uses the last parameter definition or .OPTION statement, even if that definition occurs later in the input than a reference to the parameter or option. HSPICE or HSPICE RF does not warn you when you redefine a parameter. ■ You must define a parameter before you use that parameter to define another parameter. HSPICE® User Guide: Simulation and Analysis B-2008.09 49 Chapter 4: Input Netlist and Data Entry Input Netlist File Guidelines ■ When you select design parameter names, be careful to avoid conflicts with parameterized libraries. ■ To delimit expressions, use single or double quotes. ■ Expressions cannot exceed 1024 characters. ■ For improved readability, use a double backslash preceded by a whitespace ( \\) at end of a line, to continue the line. ■ You can nest functions up to three levels. ■ Any function that you define can contain up to two arguments. ■ Use the PAR (expression or parameter) function to evaluate expressions in output statements. ■ Limitation 1: If a parameter is defined as an expression containing output signals such as v(node) or i(element), this parameter only can be used in an element value expression directly, and can not be evaluated to another parameter. For example, the following is correct: .param a='2*sqrt(V(p,n))' r1 p n '1k+a' The following definition is correct, but this definition points up the limitation and is not permitted because HSPICE generates an incorrect result. .param a='2*sqrt(v(p,n))' .param b='a+1' r1 p n '1k+b' It is best to use a user-defined function to replace the previous example, so that all of r1 and r2 are correct. .param .param r1 p n r2 p n ■ a(x)='2*sqrt(x)' b(x)='a(x)+1' '1k+a(V(p,n))' '1k+b(V(p,n))' Limitation 2: If an expression containing output signals such as v(node) or i(element) is used in an element value directly, the element only can be R, C, L, E, or G. Correct G1 1 0 cur='((1-(a0*v(gate)))/b0)' 50 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 4: Input Netlist and Data Entry Input Netlist File Guidelines Incorrect I1 1 0 cur='((1-(a0*v(gate)))/b0)' Input Netlist File Structure An input netlist file should consist of one main program. In HSPICE, an input netlist can contain one or more optional submodules. HSPICE uses a submodule (preceded by an .ALTER statement) to automatically change an input netlist file; then rerun the simulation with different options, netlist, analysis statements, and test vectors. You can use several high-level call statements (.INCLUDE,and .LIB) to structure the input netlist file modules. These statements can call netlists, model parameters, test vectors, analysis, and option macros into a file from library files or other files. The input netlist file also can call an external data file, which contains parameterized data for element sources and models. You must enclose the names of included or internally-specified files in single or double quotation when they begin with a number (0-9). Schematic Netlists HSPICE or HSPICE RF typically use netlisters to generate circuits from schematics, and accept either hierarchical or flat netlists. The process of creating a schematic involves: ■ Symbol creation with a symbol editor. ■ Circuit encapsulation. ■ Property creation. ■ Symbol placement. ■ Symbol property definition. ■ Wire routing and definition Table 7 Input Netlist File Sections Sections Examples Definition Title .TITLE The first line in the netlist is the title of the input netlist file. (HSPICE) HSPICE® User Guide: Simulation and Analysis B-2008.09 51 Chapter 4: Input Netlist and Data Entry Input Netlist File Guidelines Table 7 Input Netlist File Sections (Continued) Sections Examples Definition Set-up .OPTION .IC or .NODESET, .PARAM, .GLOBAL Sets conditions for simulation. Initial values in circuit and subcircuit. Set parameter values in the netlist. Set node name globally in netlist. Sources Sources and digital inputs Sets input stimuli (I or V element). Netlist Circuit elements .SUBKCT, .ENDS, or .MACRO, .EOM Circuit for simulation. Subcircuit definitions. Analysis .DC, .TRAN, .AC, and so on. .SAVE and .LOAD .DATA, .TEMP Statements to perform analyses. Save and load operating point information. (HSPICE) Create table for data-driven analysis. Set temperature analysis. Output .PRINT, .PROBE, .MEASURE Statements to output variables. Statement to evaluate and report user-defined functions of a circuit. Library, Model and File Inclusion .INCLUDE General include files. .MALIAS Assigns an alias to a diode, BJT, JFET, or MOSFET. (HSPICE) .MODEL Element model descriptions. .LIB Library. .OPTION SEARCH Search path for libraries and included files. (HSPICE) .OPTION BRIEF= 1 and .OPTION BRIEF= 0 Control printback to output listing. (HSPICE) 52 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 4: Input Netlist and Data Entry Input Netlist File Composition Table 7 Input Netlist File Sections (Continued) Sections Examples Definition Alter blocks (HSPICE Only) .ALIAS, .ALTER, .DEL LIB Renames a previous model. Sequence for in-line case analysis. Removes previous library selection. End of netlist .END Required statement; end of netlist. Input Netlist File Composition The HSPICE and HSPICE RF circuit description syntax is compatible with the SPICE input netlist format. Figure 5 shows the basic structure of an input netlist. Title line: First line is automatically a comment * Comments (all lines beginning with an asterisk) * Input control statements Netlist body: description of circuit topology. .MODEL statements * .OPTION statements .OPTION with option statements .PRINT and other output statements. Analysis statement (such as .POWER, .TRAN) .END Figure 5 Element and input control statements Analysis/output control statements Basic Netlist Structure The following is an example of a simple netlist file, called inv_ckt.in. It shows a small inverter test case that measures the timing behavior of the inverter. To create the circuit: 1. Define the MOSFET models for the PMOS and NMOS transistors of the inverter. 2. Insert the power supplies for both VDD and GND power rails. HSPICE® User Guide: Simulation and Analysis B-2008.09 53 Chapter 4: Input Netlist and Data Entry Input Netlist File Composition Insert the pulse source to the inverter input. This circuit uses transient analysis and produces output graphical waveform data for the input and output ports of the inverter circuit. * Sample inverter circuit * **** MOS models ***** .MODEL n1 NMOS LEVEL=3 THETA=0.4 ... .MODEL p1 PMOS LEVEL=3 ... * ***** Define power supplies and sources ***** VDD VDD 0 5 VPULSE VIN 0 PULSE 0 5 2N 2N 2N 98N 200N VGND GND 0 0 * ***** Actual circuit topology ***** M1 VOUT VIN VDD VDD p1 M2 VOUT VIN GND GND n1 * ***** Analysis statement ***** .TRAN 1n 300n * ***** Output control statements ***** .OPTION POST PROBE .PROBE V(VIN) V(VOUT) .END For a description of individual commands used in HSPICE or HSPICE RF netlists, see the HSPICE and HSPICE RF Netlist Commands chapter in the HSPICE Reference Manual: Commands and Control Options. HSPICE Topology Rules When constructing the circuit description HSPICE does not allow certain topologies. The following rules apply: 1. Every node must have a DC path to ground (all circuits must a have at least one ground not in series with a capacitor). 2. No dangling nodes (all nodes must have at least two connections). 3. No voltage loops (no voltage sources in parallel with no other elements). 4. No ideal voltage source in closed inductor loop. 5. No stacked current sources (no current sources in series). 54 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 4: Input Netlist and Data Entry Input Netlist File Composition 6. No ideal current source in closed capacitor loop. 2. 3. 1. v v v v 5. 4. 6. I I v I Title of Simulation You set the simulation title in the first line of the input file. HSPICE or HSPICE RF always reads this line, and uses it as the title of the simulation, regardless of the line’s contents. The simulation prints the title verbatim, in each section heading of the output listing file. To set the title, you can place a .TITLE statement on the first line of the netlist. However, HSPICE or HSPICE RF does not require the .TITLE syntax. The first line of the input file is always the implicit title. If any statement appears as the first line in a file, simulation interprets it as a title, and does not execute it. An .ALTER statement does not support use of the .TITLE statement. To change a title for a .ALTER statement, place the title content in the .ALTER statement itself. Comments and Line Continuation The first line of a netlist is always a comment, regardless of its first character; comments that are not the first line of the netlist require an asterisk (*) as the HSPICE® User Guide: Simulation and Analysis B-2008.09 55 Chapter 4: Input Netlist and Data Entry Input Netlist File Composition first character in a line or a dollar sign (\$) directly in front of the comment anywhere on the line. For example, * comment_on_a_line_by_itself -orHSPICE_statement \$ comment_following_HSPICE_input You can place comment statements anywhere in the circuit description. The dollar sign (\$) must be used for comments that do not begin in the first character position on a line (for example, for comments that follow simulator input on the same line). If it is not the first nonblank character, then the dollar sign must be preceded by either: ■ Whitespace ■ Comma (,) ■ Valid numeric expression. You can also place the dollar sign within node or element names. For example, * RF=1K GAIN SHOULD BE 100 \$ MAY THE FORCE BE WITH MY CIRCUIT VIN 1 0 PL 0 0 5V 5NS \$ 10v 50ns R12 1 0 1MEG \$ FEED BACK .PARAM a=1w\$comment a=1, w treated as a space and ignored .PARAM a=1k\$comment a=1e3, k is a scale factor A dollar sign is the preferred way to indicate comments because of the flexibility of its placement within the code. Line continuations require a plus sign (+) as the first character in the line that follows. Here is an example of comments and line continuation in a netlist file: .ABC Title Line (HSPICE or HSPICE RF ignores the netlist keyword * on this line because the first line is always a comment) * This is a comment line .MODEL n1 NMOS \$ this is an example of an inline comment * This is a comment line and the following line is a continuation + LEVEL=3 56 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 4: Input Netlist and Data Entry Input Netlist File Composition Element and Source Statements Element statements describe the netlists of devices and sources. Use nodes to connect elements to one another. Nodes can be either numbers or names. Element statements specify: ■ Type of device. ■ Nodes to which the device is connected. ■ Operating electrical characteristics of the device. Element statements can also reference model statements that define the electrical parameters of the element. Table 8 lists the parameters of an element statements. Table 8 Element Parameters Parameter Description elname Element name that cannot exceed 1023 characters, and must begin with a specific letter for each element type: B IBIS buffer (HSPICE Only) C Capacitor D Diode E,F,G,H Dependent current and voltage sources I Current (inductance) source J JFET or MESFET K Mutual inductor L Inductor model or magnetic core mutual inductor model M MOSFET Q BJT P Port R Resistor S, S-parameter mode T, U, W Transmission line V Voltage source X Subcircuit call node1 ... Node names identify the nodes that connect to the element. The node name begins with a letter and can contain a maximum of 1023 characters. For a listing of legal and illegal special characters that can be used in node names, see the Special Characters section, Table 3 on page 42. HSPICE® User Guide: Simulation and Analysis B-2008.09 57 Chapter 4: Input Netlist and Data Entry Input Netlist File Composition Table 8 Element Parameters (Continued) Parameter Description mname HSPICE or HSPICE RF requires a model reference name for all elements, except passive devices. pname1 ... An element parameter name identifies the parameter value that follows this name. expression Any mathematical expression containing values or parameters, such as param1 * val2 val1 ... Value of the pname1 parameter, or of the corresponding model node. The value can be a number or an algebraic expression. M=val Element multiplier. Replicates val element times, in parallel. Do not assign a negative value or zero as the M value. For descriptions of element statements for the various types of supported elements, see the chapters about individual types of elements in this user guide. Example 1 Q1234567 4000 5000 6000 SUBSTRATE BJTMODEL AREA=1.0 The preceding example specifies a bipolar junction transistor, with its collector connected to node 4000, its base connected to node 5000, its emitter connected to node 6000, and its substrate connected to the SUBSTRATE node. The BJTMODEL name references the model statement, which describes the transistor parameters. M1 ADDR SIG1 GND SBS N1 10U 100U The preceding example specifies a MOSFET named M1, where: ■ drain node=ADDR ■ gate node=SIG1 ■ source node=GND ■ substrate nodes=SBS The preceding element statement calls an associated model statement, N1. The MOSFET dimensions are width=100 microns and length=10 microns. 58 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 4: Input Netlist and Data Entry Input Netlist File Composition Example 2 M1 ADDR SIG1 GND SBS N1 w1+w l1+l The preceding example specifies a MOSFET named M1, where: ■ drain node=ADDR ■ gate node=SIG1 ■ source node=GND ■ substrate nodes=SBS The preceding element statement calls an associated model statement, N1. MOSFET dimensions are algebraic expressions (width=w1+w, and length=l1+l). Defining Subcircuits You can create a subcircuit description for a commonly-used circuit, and include one or more references to the subcircuit in your netlist. ■ Use .SUBCKT and .MACRO statements to define subcircuits within your HSPICE netlist or HSPICE RF. ■ Use the .ENDS statement to terminate a .SUBCKT statement. ■ Use the .EOM statement to terminate a .MACRO statement. ■ Use Xsubcircuit_name (the subcircuit call statement) to call a subcircuit that you previously defined in a .MACRO or .SUBCKT command in your netlist, where subcircuit_name is the element name of the subcircuit that you are calling. ■ Use the .INCLUDE statement to include another netlist as a subcircuit in the current netlist. Node Name (or Node Identifier) Conventions Nodes are the points of connection between elements in the input netlist. You can use either names or numbers to designate nodes. Node numbers can be from 1 to 999999999999999 (1-1e16); node number 0 is always ground. HSPICE or HSPICE RF ignores letters that follow numbers in node names. When the node name begins with a letter or a valid special character, the node name can contain a maximum of 1024 characters. HSPICE® User Guide: Simulation and Analysis B-2008.09 59 Chapter 4: Input Netlist and Data Entry Input Netlist File Composition The following are conventions regarding node names: ■ In addition to letters and digits, node names can include, but NOT always begin with some special characters. See the Special Characters section, Table 3 on page 42. Note that use of special characters in node names varies between HSPICE and HSPICE RF. ■ If you use braces { } in node names, HSPICE or HSPICE RF changes them to brackets [ ]. ■ You cannot use the following characters in node names: () ,=,‘, <blank> ■ You should avoid using the dollar sign (\$) after a numerical digit in a node name because HSPICE assumes whatever follows the “\$” symbol is an inline comment (see Comments and Line Continuation on page 55 for additional information). It can cause error and warning messages depending on where the node containing the “\$” is located. For example, HSPICE generates an error indicating that a resistor node is missing: R1 1\$ 2 1k Also, in this example, HSPICE issues a warning indicating that the value of resistor R1 is limited to 1e-5 and interprets the line as “R1 2 1” without a defined value: R1 2 1\$ 1k ■ The period (.) is reserved for use as a separator between a subcircuit name and a node name: subcircuitName.nodeName. If a node name contains a period, the node will be considered a top level node unless there is a valid match to a subcircuit name and node name in the hierarchy. ■ The sorting order for operating point nodes is: a-z, !, #, \$, %, *, +, -, / ■ 60 To make node names global across all subcircuits, use a .GLOBAL statement (see Global Node Names on page 65). The 0, GND, GND!, and GROUND node names all refer to the global HSPICE or HSPICE RF ground. Simulation treats nodes with any of these names as a ground node, and produces v(0) into the output files. Besides these ground nodes, all node names are regarded as separate nodes.For example, 0 and 0.3 are different nodes, 1A and 1 are different nodes, 2~ and 2 are different nodes. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 4: Input Netlist and Data Entry Input Netlist File Composition Using Wildcards on Node Names You can use wildcards to match node names. ■ The ? wildcard matches any single character. For example, 9? matches 92, 9a, 9A, and 9%. ■ The * wildcard matches any string of zero or more characters. For example: • If your netlist includes a resistor named r1 and a voltage source named vin, then .PRINT i(*) prints the current for both of these elements: i(r1) and i(vin). • And .PRINT v(o*) prints the voltages for all nodes whose names start with o; if your netlist contains nodes named in and out, this example prints only the v(out) voltage. For example, the following prints the results of a transient analysis for the voltage at the matched node name. .PRINT TRAN V(9?t*u) ■ Wildcards must begin with a letter or a number; for example, .PROBE v(*) .PROBE * .PROBE x* \$ correct format \$ incorrect format \$ correct format Here are some practical applications for these wildcards: ■ If your netlist includes a resistor named r1 and a voltage source named vin, then .PRINT i(*) prints the current for both elements i(r1) and i(vin). ■ The statement .PRINT v(o*) prints the voltages for all nodes whose names start with o; if your netlist contains nodes named in and out, this example prints only the v(out) voltage. ■ If your netlist contains nodes named 0, 1, 2, and 3, then .PRINT v(0,*) or .PRINT v(0 *) prints the voltage between node 0 and each of the other nodes: v(0,1), v(0,2), and v(0,3). ■ Wildcards can be used to set initial conditions in .IC and .NODESET statements. Node names including wildcards in .IC and .NODESET must start with “v()”. For example, .NODESET v(a*)=5. Examples The following examples use wildcards with .PRINT, .PROBE, .LPRINT, .IC and .NODESET statements. HSPICE® User Guide: Simulation and Analysis B-2008.09 61 Chapter 4: Input Netlist and Data Entry Input Netlist File Composition ■ Probe node voltages for nodes at all levels. .PROBE v(*) ■ Probe all nodes whose names start with “a”. For example: a1, a2, a3, a00, ayz. .PROBE v(a*) ■ Print node voltages for nodes at the first level and all levels below the first level, where zero-level are top-level nodes. For example: X1.A, X4.554, Xab.abc123. .PRINT v(*.*) ■ Probe node voltages for all nodes whose name start with “x” at the first level and all levels below the first level, where zero-level are top-level nodes. For example: x1.A, x4.554, xab.abc123. .PROBE v(x*.*) ■ Print node voltages for nodes whose names start with “x” at the second-level and all levels below the second level. For example: x1.x2.a, xab.xdff.in. .PRINT v(x*.*.*) ■ Match all first-level nodes with names that are exactly two characters long. For example: x1.in, x4.12. .PRINT v(x*.*.*) ■ In HSPICE RF, print the logic state of all top-level nodes, whose names start with b. For example: b1, b2, b3, b56, bac. .LPRINT (1,4) b* ■ Set transient initial conditions to all nodes. For example: .ic v(*)=val initializes nodal voltages for DC operating point analysis to nodes whose names start with “a”, such as: a1, a2, a11, a21. .nodeset v(a*)=val If one node is specified and it also matches a wildcard in .IC or .NODESET, then the specified value will override the wildcard's value. For example, if .ic v(a*)=5 v(a1)=10, then v(a1)will be 10. 62 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 4: Input Netlist and Data Entry Input Netlist File Composition Element, Instance, and Subcircuit Naming Conventions Instances and subcircuits are elements and as such, follow the naming conventions for elements. Element names in HSPICE or HSPICE RF begin with a letter designating the element type, followed by up to 1023 alphanumeric characters. Element type letters are R for resistor, C for capacitor, M for a MOSFET device, and so on (see Element and Source Statements on page 57). Subcircuit Node Names HSPICE assigns two subcircuit node names. ■ To assign the first name, HSPICE or HSPICE RF uses the (.) extension to concatenate the circuit path name with the node name—for example, X1.XBIAS.M5. Node designations that start with the same number, followed by any letter, are the same node. For example, 1c and 1d are the same node. ■ The second subcircuit node name is a unique number that HSPICE automatically assigns to an input netlist subcircuit. The ( : ) extension concatenates this number with the internal node name, to form the entire subcircuit’s node name (for example, 10:M5). The output listing file crossreferences the node name. Note: HSPICE RF does not support short names for internal subcircuits, such as 10:M5. To indicate the ground node, use either the number 0, the name GND, or !GND. Every node should have at least two connections, except for transmission line nodes (unterminated transmission lines are permitted) and MOSFET substrate nodes (which have two internal connections). Floating power supply nodes are terminated with a 1Megohm resistor and a warning message. Path Names of Subcircuit Nodes A path name consists of a sequence of subcircuit names, starting at the highest-level subcircuit call, and ending at an element or bottom-level node. Periods separate the subcircuit names in the path name. The maximum length of the path name, including the node name, is 1024 characters. HSPICE® User Guide: Simulation and Analysis B-2008.09 63 Chapter 4: Input Netlist and Data Entry Input Netlist File Composition You can use path names in .PRINT, .NODESET, and .IC statements, as another way to reference internal nodes (nodes not appearing on the parameter list). You can use the path name to reference any node, including any internal node. Subcircuit node and element names follow the rules shown in Figure 6 on page 64. 0 (CKT) 1 (X1) 3 (X3) sig24 Figure 6 2 (X2) n (abc) is circuit number (instance name) 4 (X4) sig25 sig26 Subcircuit Calling Tree, with Circuit Numbers and Instance Names In Figure 6, the path name of the sig25 node in the X4 subcircuit is X1.X4.sig25. You can use this path in HSPICE or HSPICE RF statements, such as: .PRINT v(X1.X4.sig25) Abbreviated Subcircuit Node Names In HSPICE, you can use circuit numbers as an alternative to path names, to reference nodes or elements in .PRINT, .NODESET, or .IC statements. Compiling the circuit assigns a circuit number to all subcircuits, creating an abbreviated path name: <subckt-num>:<name> Note: HSPICE RF does not recognize this type of abbreviated subcircuit name. The subcircuit name and a colon precede every occurrence of a node or element in the output listing file. For example, 4:INTNODE1 is a node named INTNODE1, in a subcircuit assigned the number 4. 64 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 4: Input Netlist and Data Entry Input Netlist File Composition Any node not in a subcircuit has a 0: prefix (0 references the main circuit). To identify nodes and subcircuits in the output listing file, HSPICE uses a circuit number that references the subcircuit where the node or element appears. Abbreviated path names let you use DC operating point node voltage output, as input in a .NODESET statement for a later run. You can copy the part of the output listing titled Operating Point Information or you can type it directly into the input file, preceded by a .NODESET statement. This eliminates recomputing the DC operating point in the second simulation. Automatic Node Name Generation HSPICE or HSPICE RF can automatically assign internal node names. To check both nodal voltages and branch currents, you can use the assigned node name when you print or plot. HSPICE or HSPICE RF supports several special cases for node assignment—for example, simulation automatically assigns node 0 as a ground node. For CSOS (CMOS Silicon on Sapphire), if you assign a value of -1 to the bulk node, the name of the bulk node is B#. Use this name to print the voltage at the bulk node. When printing or plotting current—for example .PRINT I(R1)— HSPICE inserts a zero-valued voltage source. This source inserts an extra node in the circuit named Vnn, where nn is a number that HSPICE (or HSPICE RF) automatically generates; this number appears in the output listing file. Global Node Names The .GLOBAL statement globally assigns a node name, in HSPICE or HSPICE RF. This means that all references to a global node name, used at any level of the hierarchy in the circuit, connect to the same node. The most common use of a .GLOBAL statement is if your netlist file includes subcircuits. This statement assigns a common node name to subcircuit nodes. Another common use of .GLOBAL statements is to assign power supply connections of all subcircuits. For example, .GLOBAL VCC connects all subcircuits with the internal node name VCC. Ordinarily, in a subcircuit, the node name consists of the circuit number, concatenated to the node name. When you use a .GLOBAL statement, HSPICE or HSPICE RF does not concatenate the node name with the circuit number, and assigns only the global name. You can then exclude the power node name in the subcircuit or macro call. HSPICE® User Guide: Simulation and Analysis B-2008.09 65 Chapter 4: Input Netlist and Data Entry Input Netlist File Composition Circuit Temperature To specify the circuit temperature for an HSPICE simulation, use the .TEMP statement, the TEMP parameter in the .DC, .AC, and .TRAN statements, or the TEMP/TEMPER parameter in the first column of the .DATA statement. HSPICE compares the circuit simulation temperature against the reference temperature in the TNOM control option. HSPICE or HSPICE RF uses the difference between the circuit simulation temperature and the TNOM reference temperature to define derating factors for component values. In HSPICE RF, you can use multiple .TEMP statements to specify multiple temperatures for different portions of the circuit. HSPICE permits only one temperature for the entire circuit. Multiple .TEMP statements in a circuit behave as a sweep function. Data-Driven Analysis In data-driven analysis, you can modify any number of parameters, then use the new parameter values to perform an operating point, DC, AC, or transient analysis. An array of parameter values can be either inline (in the simulation input file) or stored as an external ASCII file. The .DATA statement associates a list of parameter names with corresponding values in the array. HSPICE supports the entire functionality of the .DATA statement. However, HSPICE RF supports .DATA only for: ■ Data-driven analysis. ■ Inline or external data files. For more details about using the .DATA statement in different types of analysis, see Chapter 12, Initializing DC/Operating Point Analysis and Chapter 14, Transient Analysis. Library Calls and Definitions To create and read from libraries of commonly-used commands, device models, subcircuit analysis, and statements in library files, use the .LIB call statement. As HSPICE or HSPICE RF encounters each .LIB call name in the main data file, it reads the corresponding entry from the designated library file, until it finds an .ENDL statement. In HSPICE, you can also place a .LIB call statement in an .ALTER block. 66 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 4: Input Netlist and Data Entry Input Netlist File Composition Library Building Rules ■ A library cannot contain .ALTER statements. ■ A library can contain nested .LIB calls to itself or to other libraries. If you use a relative path in a nested .LIB call, the path starts from the directory of the parent library, not from the work directory. If the path starts from the work directory, HSPICE can also find the library, but it prints a warning. The depth of nested calls is limited only by the constraints of your system configuration. ■ A library cannot contain a call to a library of its own entry name, within the same library file. ■ A HSPICE or HSPICE RF library cannot contain the .END statement. ■ .ALTER processing cannot change .LIB statements, within a file that an .INCLUDE statement calls. Automatic Library Selection (HSPICE) Automatic library selection searches a sequence of up to 40 directories. The hspice.ini file sets the default search paths. Use this file for directories that you want HSPICE to always search. HSPICE searches for libraries in the order specified in .OPTION SEARCH statements. When HSPICE encounters a subcircuit call, the search order is: 1. Read the input file for a .SUBCKT or .MACRO with the specified call name. 2. Read any .INC files or .LIB files for a .SUBCKT or .MACRO with the specified call name. 3. Search the directory containing the input file for the call_name.inc file. 4. Search the directories in the .OPTION SEARCH list. You can use the HSPICE library search and selection features to simulate process corner cases, using .OPTION SEARCH =‘<libdir>’ to target different process directories. For example, if you store an input or output buffer subcircuit in a file named iobuf.inc, you can create three copies of the file, to simulate fast, slow and typical corner cases. Each file contains different HSPICE transistor models, representing the different process corners. Store these files (all named iobuf.inc) in separate directories. HSPICE® User Guide: Simulation and Analysis B-2008.09 67 Chapter 4: Input Netlist and Data Entry Input Netlist File Composition Defining Parameters The .PARAM statement defines parameters. Parameters in HSPICE or HSPICE RF are names that have associated numeric values. You can also use either of the following specialized methods to define parameters: ■ Predefined Analysis ■ Measurement Parameters Predefined Analysis HSPICE or HSPICE RF provides several specialized analysis types, which require a way to control the analysis. For the syntax used in these .PARAM commands, see the description of the .PARAM command in the HSPICE Reference Manual: Commands and Control Options. HSPICE or HSPICE RF supports the following predefined analysis parameters: ■ Temperature functions (fn) ■ Optimization guess/range ■ Monte Carlo functions HSPICE also supports the following predefined parameter types, that HSPICE RF does not support: ■ frequency ■ time Measurement Parameters A .MEASURE statement produces a measurement parameter. In general, the rules for measurement parameters are the same as those for standard parameters. However, measurement parameters are not defined in a .PARAM statement, but directly in the .MEASURE statement. For more information, see .MEASURE Parameter Types on page 318. Outputting Pass/Fail Measure Data You can use .measure to create a logic equation that describes the pass/fail condition. It will output a 0/1 value for pass/fail in the .mt0 file. For example: .meas m1 find v(1) at 10n .meas m2 find v(2) at 10n .meas pass param="(m1 > 1) && (m2 < 2)" 68 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 4: Input Netlist and Data Entry Input Netlist File Composition Altering Design Variables and Subcircuits The following rules apply when you use an .ALTER block to alter design variables and subcircuits in HSPICE. This section does not apply to HSPICE RF. ■ If the name of a new element, .MODEL statement, or subcircuit definition is identical to the name of an original statement of the same type, then the new statement replaces the old. Add new statements in the input netlist file. ■ You can alter element and .MODEL statements within a subcircuit definition. You can also add a new element or .MODEL statement to a subcircuit definition. To modify the topology in subcircuit definitions, put the element into libraries. To add a library, use .LIB; to delete, use .DEL LIB. ■ If a parameter name in a new .PARAM statement in the .ALTER module is identical to a previous parameter name, then the new assigned value replaces the old value. ■ If you used parameter (variable) values for elements (or model parameter values) when you used .ALTER, use the .PARAM statement to change these parameter values. Do not use numerical values to redescribe elements or model parameters. ■ If you used an .OPTION statement (in an original input file or a .ALTER block) to turn on an option, you can turn that option off. ■ Each .ALTER simulation run prints only the actual altered input. A special .ALTER title identifies the run. ■ .ALTER processing cannot revise .LIB statements within a file that an .INCLUDE statement calls. However, .ALTER processing can accept .INCLUDE statements, within a file that a .LIB statement calls. Using Multiple .ALTER Blocks This section does not apply to HSPICE RF. ■ For the first simulation run, HSPICE reads the input file, up to the first .ALTER statement, and performs the analyses up to that .ALTER statement. ■ After it completes the first simulation, HSPICE reads the input between the first .ALTER statement, and either the next .ALTER statement or the .END statement. ■ HSPICE then uses these statements to modify the input netlist file. HSPICE® User Guide: Simulation and Analysis B-2008.09 69 Chapter 4: Input Netlist and Data Entry Input Netlist File Composition ■ HSPICE then resimulates the circuit. ■ For each additional .ALTER statement, HSPICE performs the simulation that precedes the first .ALTER statement. ■ HSPICE then performs another simulation, using the input between the current .ALTER statement, and either the next .ALTER statement or the .END statement. If you do not want to rerun the simulation that precedes the first .ALTER statement, every time you run an .ALTER simulation, then do the following: 1. Put the statements that precede the first .ALTER statement, into a library. 2. Use the .LIB statement in the main input file. 3. Put a .DEL LIB statement in the .ALTER section, to delete that library for the .ALTER simulation run. Connecting Nodes Use a .CONNECT statement to connect two nodes in your HSPICE netlist, so that simulation evaluates two nodes as only one node. Both nodes must be at the same level in the circuit design that you are simulating: you cannot connect nodes that belong to different subcircuits. You also cannot use this statement in HSPICE RF. Deleting a Library Use a .DEL LIB statement to remove library data from memory. The next time you run a simulation the .DEL LIB statement removes the .LIB call statement, with the same library number and entry name from memory. You can then use a .LIB statement to replace the deleted library. You can use a .DEL LIB statement with a .ALTER statement. HSPICE RF does not support the .ALTER statement. Ending a Netlist An .END statement must be the last statement in the input netlist file. Text that follows the .END statement is a comment, and has no effect on the simulation. 70 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 4: Input Netlist and Data Entry Input Netlist File Composition An input file that contains more than one simulation run must include an .END statement for each simulation run. You can concatenate several simulations into a single file. Condition-Controlled Netlists (IF-ELSE) You can use the IF-ELSE structure to change the circuit topology, expand the circuit, set parameter values for each device instance, select different model cards, reference subcircuits, or define subcircuits in each IF-ELSE block. .if (condition1) <statement_block1> # The following statement block in {braces} is # optional, and you can repeat it multiple times: { .elseif (condition2) <statement_block2> } # The following statement block in [brackets] # is optional, and you cannot repeat it: [ .else <statement_block3> .endif The following example provides a quick overview of using the IF-ELSE construct: HSPICE® User Guide: Simulation and Analysis B-2008.09 71 Chapter 4: Input Netlist and Data Entry Input Netlist File Composition * .tran 1n 100ns .option post .param variable = 2 vin1 source 0 0 pwl 0ns 0v 20ns 0v 21ns 5v 30ns 5v 31ns 0v 40ns + 0v 41ns 5v 50ns 5v 70ns 5v 71ns 0v 80ns 0v 81ns 5v + 90ns 5v 91ns 0v 100ns 0v Rin source 1 1000 x1 1 2 resistor r1 2 0 1k .subckt resistor 1 2 .if (variable==1) r22 1 2 1k .elseif (variable==2) r22 1 2 2k .else r22 1 2 3k .endif .ends .print v(2) i(1) .alter .param variable=1 .alter .param variable=3 .end Guidelines for Using IF-ELSE Blocks The following guidelines aid in usage of the .IF, .ELSE-IF, or .ELSE. ■ In an .IF, .ELSEIF, or .ELSE condition statement, complex Boolean expressions must not be ambiguous. For example, change (a==b && c>=d) to ( (a==b) && (c>=d) ). ■ In an IF, ELSEIF, or ELSE statement block, you can include most valid HSPICE (not HSPICE RF) analysis and output statements. The exceptions are: • .END, .ALTER, .GLOBAL, .DEL LIB, .MALIAS, .ALIAS, .LIST, .NOLIST, and .CONNECT statements. • search, d_ibis, d_imic, d_lv56, biasfi, modsrh, cmiflag, nxx, and brief options. ■ ■ 72 You can include IF-ELSEIF-ELSE statements in subcircuits and subcircuits in IF-ELSEIF-ELSE statements. You can use IF-ELSEIF-ELSE blocks to select different submodules to structure the netlist (using .INC, .LIB, and .VEC statements). HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 4: Input Netlist and Data Entry Using Subcircuits ■ If two or more models in an IF-ELSE block have the same model name and model type, they must also be the same revision level. ■ Parameters in an IF-ELSE block do not affect the parameter value within the condition expression. HSPICE or HSPICE RF updates the parameter value only after it selects the IF-ELSE block. ■ You can nest IF-ELSE blocks. ■ You can include .SUBCKT and .MACRO statements within an IF-ELSE block. ■ You can include an unlimited number of ELSEIF statements within an IF-ELSE block. ■ You cannot use an IF-ELSE block within another statement. In the following example, HSPICE or HSPICE RF does not recognize the IF-ELSE block as part of the resistor definition: r10 .if (r_val>10k) + 10k .else + r_val .endif Using Subcircuits Reusable cells are the key to saving labor in any CAD system. This also applies to circuit simulation, in HSPICE or HSPICE RF. ■ To create and simulate a reusable circuit, construct it as a subcircuit. ■ Use parameters to expand the utility of a subcircuit. Traditional SPICE includes the basic subcircuit, but does not provide a way to consistently name nodes. However, HSPICE or HSPICE RF provides a simple method for naming subcircuit nodes and elements: use the subcircuit call name as a prefix to the node or element name. In HSPICE RF, you cannot replicate output commands within subcircuit (subckt) definitions. HSPICE® User Guide: Simulation and Analysis B-2008.09 73 Chapter 4: Input Netlist and Data Entry Using Subcircuits MP MN INV Figure 7 Subcircuit Representation The following input creates an instance named X1 of the INV cell macro, which consists of two MOSFETs, named MN and MP: X1 IN OUT VD_LOCAL VS_LOCAL inv W=20 .MACRO INV IN OUT VDD VSS W=10 L=1 DJUNC=0 MP OUT IN VDD VDD PCH W=W L=L DTEMP=DJUNC MN OUT IN VSS VSS NCH W=’W/2’ L=L DTEMP=DJUNC .EOM Note: To access the name of the MOSFET, inside of the INV subcircuit that X1 calls, the names are X1.MP and X1.MN. So to print the current that flows through the MOSFETs, use .PRINT I (X1.MP). Hierarchical Parameters You can use two hierarchical parameters, the M (multiply) parameter and the S (scale) parameter. M (Multiply) Parameter The most basic HSPICE or HSPICE RF subcircuit parameter is the M (multiply) parameter. This keyword is common to all elements, including subcircuits, except for voltage sources. The M parameter multiplies the internal component values. This, in effect, creates parallel copies of the element. For example, if you have an invertor and specify M=2, then HSPICE multiplies the internal component by 2. The M parameter multiplies the internal 74 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 4: Input Netlist and Data Entry Using Subcircuits component values, which, in effect, creates parallel copies of the element. To simulate 32 output buffers switching simultaneously, you need to place only one subcircuit; for example, X1 in out buffer M=32 X1 in out inv M=2 M=8 mp out in vdd pch W=10 L=1 M=4 M=6 mn out in vss nch W=5 L=1 M=3 UNEXPANDED Figure 8 EXPANDED How Hierarchical Multiply Works Multiply works hierarchically. For a subcircuit within a subcircuit, HSPICE or HSPICE RF multiplies the product of both levels. Values of M must be positive. Do not assign a negative value or zero as the M value. S (Scale) Parameter To scale a subcircuit, use the S (local scale) parameter. This parameter behaves in much the same way as the M parameter in the preceding section. .OPTION hier_scale=value .OPTION scale=value X1 node1 node2 subname S=valueM parameter The OPTION HIER_SCALE statement defines how HSPICE or HSPICE RF interprets the S parameter, where value is either: ■ 0 (the default), indicating a user-defined parameter, or ■ 1, indicating a scale parameter. HSPICE® User Guide: Simulation and Analysis B-2008.09 75 Chapter 4: Input Netlist and Data Entry Using Subcircuits The .OPTION SCALE statement defines the original (default) scale of the subcircuit. The specified S scale is relative to this default scale of the subcircuit. The scale in the subname subcircuit is value*scale. Subcircuits can originate from multiple sources, so scaling is multiplicative (cumulative) throughout your design hierarchy. x1 a y inv S=1u subckt inv in out x2 a b kk S=1m .ends In this example: ■ HSPICE or HSPICE RF scales the X1 subcircuit by the first S scaling value, 1u*scale. ■ Because scaling is cumulative, X2 (a subcircuit of X1) is then scaled, in effect, by the S scaling values of both X1 and X2: 1m*1u*scale. Using Hierarchical Parameters to Simplify Simulation You can use the hierarchical parameter to simplify simulations. An example is shown in the following listing and Figure 9 on page 77. X1 D Q Qbar CL CLBAR dlatch flip=0 .macro dlatch + D Q Qbar CL CLBAR flip=vcc .nodeset v(din)=flip xinv1 din qbar inv xinv2 Qbar Q inv m1 q CLBAR din nch w=5 l=1 m2 D CL din nch w=5 l=1 .eom 76 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 4: Input Netlist and Data Entry Using Subcircuits Q clbar cl Q D din .Nodeset Figure 9 D Latch with Nodeset HSPICE does not limit the size or complexity of subcircuits; they can contain subcircuit references, and any model or element statement. However, in HSPICE RF, you cannot replicate output commands within subcircuit definitions. To specify subcircuit nodes in .PRINT statements, specify the full subcircuit path and node name. You can print the hierarchical parameter using a .print/.probe/.measure statement. For example: x1 1 0 sub1 .subckt sub1 n1 n2 .param p1=1 ... .ends .tran ... .print tran par('x1.p1') .measure tram m1 param='x1.p1' Undefined Subcircuit Search (HSPICE) If a subcircuit call is in a data file that does not describe the subcircuit, HSPICE automatically searches directories in the following order: 1. Present directory for the file. 2. Directories specified in .OPTION SEARCH = “directory_path_name” statements. 3. Directory where the Discrete Device Library is located. HSPICE® User Guide: Simulation and Analysis B-2008.09 77 Chapter 4: Input Netlist and Data Entry Using Subcircuits HSPICE searches for the model reference name file that has an .inc suffix. For example, if the data file includes an undefined subcircuit, such as X 1 1 2 INV, HSPICE searches the system directories for the inv.inc file and when found, places that file in the calling data file. Troubleshooting Subcircuit Node Issues Duplicate Node Message In the .SUBCKT definition, if HSPICE finds two or more node names that are similar, it will issue the following error: **error** subcircuit definition duplicates node x1234 **error** .ends } card missing at readin In the following example, for the .SUBCKT definition, the node “in” is defined twice. The second definition of the node “in” is a duplicate of the first node, which is not allowed in HSPICE.: .subckt ABC in in out . . .ends Duplicating Ports To create duplicate ports in HSPICE you can define them in the instance definition of the subcircuit. For example: .subckt DUP A B C D . . .ends If you want to make node “B” a duplicate of node “A” then the instance definition should look like: XDUP A A C D DUP Using Assigned Circuit Numbers instead of Full Path Node Names In HSPICE, you can use circuit numbers as an alternative to the full subcircuit path names to reference nodes or elements in .PRINT, .NODESET or .IC statements. 78 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 4: Input Netlist and Data Entry Subcircuit Call Statement Discrete Device Libraries HSPICE assigns a circuit number to all subcircuits in the netlist. The circuit number can be used to abbreviate the path name, as follows: <subckt-num>:<name> You can find the abbreviated path name information in the *.pa0 file. Nodes that are not in a subcircuit have a 0 prefix which references the main or top level circuit. Subcircuit Call Statement Discrete Device Libraries The Synopsys Discrete Device Library (DDL) is a collection of HSPICE device models of discrete components, which you can use with HSPICE. The \$<installdir>/parts directory contains the various subdirectories that form the DDL. Synopsys used its own ATEM discrete device characterization system to derive the BJT, MESFET, JFET, MOSFET, and diode models from laboratory measurements. The behavior of op-amp, timer, comparator, SCR, and converter models closely resembles that described in manufacturers’ data sheets. HSPICE has a built-in op-amp model generator. Note: The value of the \$INSTALLDIR environment variable is the pathname to the directory where you installed HSPICE. This installation directory contains subdirectories, such as /parts and /bin. It also contains certain files, such as a prototype meta.cfg file, and the license files. DDL Library Access To include a DDL library component in a data file, use the X subcircuit call statement with the DDL element call. The DDL element statement includes the model name, which the actual DDL library file uses. For example, the following element statement creates an instance of the 1N4004 diode model: X1 2 1 D1N4004 Where D1N4004 is the model name. See Element and Source Statements on page 57 and the HSPICE Elements and Device Models Manual for descriptions of element statements. Optional parameter fields in the element statement can override the internal specification of the model. For example, for op-amp devices, you can override HSPICE® User Guide: Simulation and Analysis B-2008.09 79 Chapter 4: Input Netlist and Data Entry Subcircuit Call Statement Discrete Device Libraries the offset voltage, and the gain and offset current. Because the DDL library devices are based on HSPICE circuit-level models, simulation automatically compensates for the effects of supply voltage, loading, and temperature. HSPICE or HSPICE RF accesses DDL models in several ways: ■ The installation script creates an hspice.ini initialization file. ■ HSPICE or HSPICE RF writes the search path for the DDL and vendor libraries into a .OPTION SEARCH=‘<lib_path>’ statement. This provides immediate access to all libraries for all users. It also automatically includes the models in the input netlist. If the input netlist references a model or subcircuit, HSPICE or HSPICE RF searches the directory to which the DDLPATH environment variable points for a file with the same name as the reference name. This file is an include file so its filename suffix is .inc. HSPICE installation sets the DDLPATH variable in the meta.cfg configuration file. ■ Set .OPTION SEARCH=‘<lib_path>’ in the input netlist. Use this method to list the personal libraries to search. HSPICE first searches the default libraries referenced in the hspice.ini file, then searches libraries in the order listed in the input file. ■ Directly include a specific model, using the .INCLUDE statement. For example, to use a model named T2N2211, store the model in a file named T2N2211.inc, and put the following statement in the input file: .INCLUDE <path>/T2N2211.inc This method requires you to store each model in its own .inc file, so it is not generally useful. However, you can use it to debug new models, when you test only a small number of models. Vendor Libraries The vendor library is the interface between commercial parts and circuit or system simulation. ■ ■ 80 ASIC vendors provide comprehensive cells, corresponding to inverters, gates, latches, and output buffers. Memory and microprocessor vendors supply input and output buffers. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 4: Input Netlist and Data Entry Subcircuit Call Statement Discrete Device Libraries ■ Interface vendors supply complete cells for simple functions and output buffers, to use in generic family output. ■ Analog vendors supply behavioral models. To avoid name and parameter conflicts, models in vendor cell libraries should be within the subcircuit definitions. x1 in out vdd vss buffer_f .OPTION search=‘/usr/lib/vendor’ /usr/lib/vendor/buffer_f.inc /usr/lib/vendor/skew.dat .macro buffer_f in out vdd vss .lib ‘/usr/lib/vendor/skew.dat’ ff .lib ff \$ fast model .param vendor_xl=-.1u .inc ‘/usr/lib/vendor/model.dat’ .endl ff .inc ‘/usr/lib/vendor/buffer.inc’ .eom /usr/lib/vendor/buffer.inc /usr/lib/vendor/model.dat .model nch nmos level=28 + xl=vendor_xl ... Figure 10 .macro buffer in out vdd vss m1 out in vdd vdd nch w=10 l=1 ... Vendor Library Usage Subcircuit Library Structure The .OPTION SEARCH command is an implicit include command. The include file can contain .lib calls in addition to the subcircuit definition. (See Figure 10 for a graphic view.) Your library structure must adhere to the .INCLUDE statement specification in the implicit subcircuit. You can use this statement to specify the directory that contains the <subname>.inc subcircuit file, and then reference the <subname> in each subcircuit call. The component naming conventions for each subcircuit is: <subname>.inc Store the subcircuit in a directory that is accessible by a.OPTION SEARCH=‘<lib_path>’ statement. HSPICE® User Guide: Simulation and Analysis B-2008.09 81 Chapter 4: Input Netlist and Data Entry Post-Layout Back-Annotation Create subcircuit libraries in a hierarchy. Typically, the top-level subcircuit fully describes the input/output buffer; any hierarchy is buried inside. The buried hierarchy can include model statements, lower-level components, and parameter assignments. Your library cannot use .LIB or .INCLUDE statements anywhere in the hierarchy. Post-Layout Back-Annotation The HSPICE parser enables the parsing and annotating of parasitic elements. HSPICE supports back-annotation of two types of parasitic netlist formats: ■ Standard Parasitic Format (SPF) ■ Standard Parasitic Exchange Format (SPEF) The parasitic netlist describes the interconnect delay and load, due to parasitic resistance and capacitance. Parasitics can be represented on a net-by-net basis from a simple lumped capacitance to a fully distributed resistance capacitance tree. Invoking Post-Layout Back-Annotation The enhanced parser has different format for warning/error message. It is similar to RF or Fast-Spice and stricter on the syntax than the original HSPICE parser but produces the same result once the net-list is accepted. To annotate circuits, HSPICE should be launched in the following way: hspice -i inputfile -o output -x The following is a list of back-annotation options that you can use in HSPICE: ■ .OPTION BA_FILE = “filename”: Full parasitic expansion. Filename is the name of the file that contains parasitic information in SPEF or DSPF format. ■ .OPTION BA_ACTIVE = “active_net_filename”: Conducts selective parasitic expansion. active_net_filename is the name of the file that contains information about active nets. You must use this option with BA_FILE, or it has no effect. ■ .OPTION BA_ERROR: the mode of error handling on nets. • • 2. NO: don't expand anything on the net • 82 1. EXIT: terminate simulation with error 3. LUMPCAP (default): only add the total lumped net capacitance HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 4: Input Netlist and Data Entry Post-Layout Back-Annotation • ■ 4. YES: expand whatever can be expanded .OPTION BA_TERMINAL: the terminal mapping with the format "terminal_name_in_file recognized_name", e.g., "ba_terminal = Cmy_gate SRC". Table 9 Default rules for element terminal names Terminal Index M, J Elements Q Elements R,C,D Elements 1 D* C* A*, P* 2 G* B* M*, B* C*, N* 3 S* E* S* 4 B* S* n/a HSPICE® User Guide: Simulation and Analysis B-2008.09 83 Chapter 4: Input Netlist and Data Entry Post-Layout Back-Annotation DSPF and SPEF File Structures DSPF File Structure The DSPF standard is published by Open Verilog International (OVI). DSPF_file ::= *|DSPF{version} {*|DESIGN design_name} {*|DATE date} {*|VENDOR vendor} {*|PROGRAM program_name} {*|VERSION program_version} {*|DIVIDER divider} {*|DELIMITER delimiter} .SUBCKT *|GROUND_NET {path divider} net_name *|NET {path divider} net_name || {path divider} instance_name || pin_name net_capacitance *|P (pin_name pin_type pinCap {resistance {unit} {O} capacitance {unit} {F}} {x_coordinate y_coordinate}) || *|I {path divider} instance_name delimiter pin_name {path divider} instance_name pin_name pin_type pinCap {resistance {unit} {O} capacitance {unit}{F}} {x_coordinate y_coordinate} *|S ({path divider} net_name || {path divider} instance_name delimiter pin_name || pin_name instance_number {x_coordinate y_coordinate}) capacitor_statements resistor_statements subcircuit_call_statements .ENDS {.END} 84 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 4: Input Netlist and Data Entry Post-Layout Back-Annotation SPEF File Structure The IEEE-1481 specification requires the following file structure in a SPEF file. For the current release, only the only typical set (triple value SPEF file) is annotated. Parameters in [brackets] are optional: SPEF_file ::= *SPEF version *DESIGN design_name *DATE date *VENDOR vendor *PROGRAM program_name *VERSION program_version *DESIGN_FLOW flow_type {flow_type} *DIVIDER divider *DELIMITER delimiter *BUS_DELIMITER bus_prefix bus_suffix *T_UNIT time_unit NS|PS *C_UNIT capacitance_unit FF|PF *R_UNIT resistance_unit OHM|KOHM *L_UNIT inductance_unit HENRY|MH|UH [*NAME_MAP name_index name_id|bit|path|name|physical_ref] [*POWER_NETS logical_power_net physical_power_net ...] [*GROUND_NETS ground_net ...] [*PORTS logical_port I|B|O *C coordinate ... *L par_value *S rising_slew falling_slew [low_threshold high_threshold] *D cell_type] [*PHYSICAL_PORTS [physical_instance delimiter] physical_port I|B|O *C coordinate ... *L par_value *S rising_slew falling_slew [low_threshold high_threshold] *D cell_type] [*DEFINE logical_instance design_name | *PDEFINE physical_instance design_name] *D_NET net_path total_capacitance [*V routing_confidence] [*CONN *P [logical_instance delimiter] logical_port|physical_port I|B|O *C coordinate ... *L par_value *S rising_slew falling_slew [low_threshold high_threshold] *D cell_type HSPICE® User Guide: Simulation and Analysis B-2008.09 85 Chapter 4: Input Netlist and Data Entry Post-Layout Back-Annotation | *I [physical_instance delimiter] logical_pin|physical_node I|B|O *C coordinate ... *L par_value *S rising_slew falling_slew [low_threshold high_threshold] *D cell_type *N net_name delimiter net_number coordinate [*CAP cap_id node1 [node2] capacitance] [*RES res_id node1 node2 resistance] [*INDUC induc_id node1 node2 inductance] *END 86 HSPICE® User Guide: Simulation and Analysis B-2008.09 5 Using Interactive Mode 5 This chapter describes how to use the interactive mode in HSPICE. Note: Interactive mode is not supported in HSPICE RF. Invoking Interactive Mode You start interactive mode using the hspice executable in the \$installdir/<arch> directory (for example, \$installdir/sparcOS5). To start the interactive mode, from the command prompt, type: % hspice -I HSPICE > The interactive environment functions from a special HSPICE-shell. You can use many commands while in this environment to simplify your design work. Quitting Interactive Mode You quit an interactive mode session by entering: HSPICE > quit Executing an Interactive Script You can also use interactive commands in a command script file. To execute an interactive script, from the command prompt, type: % hspice -I -L command_script HSPICE® User Guide: Simulation and Analysis B-2008.09 87 Chapter 5: Using Interactive Mode Examples Where <command_script> is the name of the file containing the interactive commands. Examples The examples in this section examples show you how to use the interactive environment commands. Getting Help You use the help command to show the interactive mode syntax; for example, % hspice -I HSPICE > help list [lineno] input edit ls [directory] load filename run pwd cd directory info outflag set outflag <true/false> save <netlist/command> filename quit help dc [...statement] (like in the netlist) ac [...statement] (like in the netlist) tran [...statement] (like in the netlist) op measure [...statement] (like in the netlist) print <tran/ac/dc> <v/vm/vr/vi/vp/vdb> Creating a Netlist You use the input command to create a netlist by using the vi text editor; for example, 88 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 5: Using Interactive Mode Examples % hspice -I HSPICE > input R1 1 0 2 V1 1 0 3 .print I(R1) .end Save the file and exit vi. Specifying an Analysis You use the ac, dc, or tran command to specify an analysis; for example, HSPICE > dc v1 -5v 5v 0.5v Running an Analysis You use the run command to simulate a netlist; for example, HSPICE > run > info: ***** hspice job concluded HSPICE outputs the simulation results. This output is equivalent to a .lis file. Viewing a Netlist You use the list command to view a netlist; for example, HSPICE > list 1 * this is an interactive mode example 2 3 R1 1 0 2 4 V1 1 0 3 5 .print I(R1) 6 .end Loading and Running an Existing Netlist Use the load command to read an existing netlist; for example, to load a netlist named “tt1.sp“: % hspice -I HSPICE > load tt1 HSPICE® User Guide: Simulation and Analysis B-2008.09 89 Chapter 5: Using Interactive Mode Examples Use the list command to view a netlist; for example, to view the tt1.sp netlist: HSPICE > list 1 * this is an interactive mode example 2 3 R1 1 0 2 4 V1 1 0 3 5 .print I(R1) 6 .end Use the dc command to specify an analysis and then run HSPICE: HSPICE > dc v1 -5v 5v 0.5v HSPICE > run > info: ***** hspice job concluded Use the list command to view a netlist again. Notice that the DC analysis is in the interactive mode netlist. The original netlist, tt1.sp, is unchanged. HSPICE > list 1 * this is an interactive mode example 2 3 R1 1 0 2 4 V1 1 0 3 5 .print I(R1) 6 .dc v1 -5v 5v 0.5v 7 .end Use the run command to simulate the netlist: HSPICE > run > info: ***** hspice job concluded Use the cd command to change the current working directory to /home/usr: HSPICE > cd /home/usr Use the pwd command to print the full pathname of the current directory: HSPICE > pwd > /home/usr Use the quit command to terminate the interactive mode: HSPICE > quit % Using Environment Commands Use the load command to read netlist “tt3.sp” and the list command to view it: 90 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 5: Using Interactive Mode Examples % hspice -I HSPICE > load tt3.sp HSPICE > list R1 1 0 2 V1 1 0 3 .print I(R1) .param a=10, t=24 .dc v(1) -5v 5v 0.5v .end Use the ls command to list the files in the current working directory: HSPICE > ls tt.sp tt.sw0 : Use the set outflag command to prevent printing simulation results to stdout (the default is true): HSPICE > set outflag false HSPICE > run Use the info outflag command to view the current setting of outflag: HSPICE > info outflag false HSPICE > quit % Recording and Saving Interactive Commands to a File Use the load command to read netlist “tt6.sp” and print the full pathname of the current directory: % hspice -I HSPICE > load tt6.sp HSPICE > pwd Write all interactive commands entered to file int1.cmd: HSPICE® User Guide: Simulation and Analysis B-2008.09 91 Chapter 5: Using Interactive Mode Examples HSPICE > save command int1 HSPICE > ls int1.cmd tt6.sp tt6.sw0 HSPICE > input R1 1 0 2 V1 1 0 3 .print I(R1) .end HSPICE > save netlist ex.sp HSPICE > ls int1.cmd tt6.sp tt6.sw0 ex.sp HSPICE > quit % Quit interactive mode and return to the system prompt: Printing a Voltage Value During Simulation Here’s an example where a voltage value is printed during simulation: 92 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 5: Using Interactive Mode Examples % hspice -I HSPICE > load tt2.sp HSPICE > list 1 * this is an interactive mode example 2 3 R1 1 0 2 4 V1 1 0 3 5 .print I(R1) 6 .dc v1 -5v 5v 0.5v HSPICE > print dc v(1,0) HSPICE > run v(1, 0) 0.000000 v(1, 0) 0.000000 v(1, 0) 0.000000 v(1, 0) 0.000000 v(1, 0) 0.000000 v(1, 0) 0.000000 v(1, 0) 0.000000 v(1, 0) 0.000000 v(1, 0) 0.000000 v(1, 0) 0.000000 v(1, 0) 0.000000 v(1, 0) 0.000000 v(1, 0) 0.000000 v(1, 0) 0.000000 v(1, 0) 0.000000 v(1, 0) 0.000000 v(1, 0) 0.000000 v(1, 0) 0.000000 v(1, 0) 0.000000 v(1, 0) 0.000000 v(1, 0) 0.000000 >info: ***** hspice job concluded HSPICE > quit % Using a Command File to Run HSPICE in Interactive Mode You use the -I -L arguments to invoke interactive mode on a command file and run it; for example, % hspice -I -L int1.cmd HSPICE® User Guide: Simulation and Analysis B-2008.09 93 Chapter 5: Using Interactive Mode Examples Running Multiple Testcases If you want to run multiple testcases and save the license check in and check out times, you can use the command file similar the following example. Using any text editor, create a command file named bat.cmd containing these entries: load tt.sp run load qq.sp run quit Run HSPICE in interactive mode to execute bat.cmd: % hspice -I -L bat.cmd ... % ls tt.sp tt.sw0 qq.sp qq.sw0 You will find that a license is checked out only one time and HSPICE simulates both tt.sp and qq.sp netlists. 94 HSPICE® User Guide: Simulation and Analysis B-2008.09 6 6 HSPICE GUI for Windows Describes how to use the HSPICE GUI for Windows. To open and install the GUI, click on the HSPUI icon. Figure 11 shows the directory structure for the HSPICE GUI for Windows. Design dir Sim. input *.sp Figure 11 Design Config *.cfg Raw output .tr#,.ac#,.sw# Measures .mt#,.ma#,.ms# Sim. output .lis Directory Structure This appendix is a organized as follows: ■ Working with Designs ■ Configuring the HSPICE GUI for Windows ■ Running Multiple Simulations ■ Metaencrypt and Converter Utilities, Client/Server Operation ■ Troubleshooting Guide Working with Designs A new design can be created in several ways. The Launcher allows you to browse for an input file for HSPICE, which has the default file suffix .sp. Click the Launcher Open button to display a standard file browser. HSPICE® User Guide: Simulation and Analysis B-2008.09 95 Chapter 6: HSPICE GUI for Windows Working with Designs Selecting a file of the type <design>.sp causes the Launcher to display the main form, which contains the following items: ■ input filename ■ design title (the first line of the file design.sp) ■ output filename ■ HSPICE and AvanWaves version Table 10 Design Commands in the Launcher Command Description File > Save Configuration Saves the current design launcher configuration <LastDesigns> Lists the last five designs opened File > Exit Exits the Launcher The Launcher checks on the status of a given design when it is opened. If the input file exists, the Simulate button is active. If the listing file exists for the design, the Edit Listing button is active. The Edit Netlist and AvanWaves buttons are always active. You do not need to save a design to Simulate or view the results of a simulation with AvanWaves. Figure 12 on page 97 shows the main window of the Launcher. 96 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 6: HSPICE GUI for Windows Configuring the HSPICE GUI for Windows Figure 12 Launcher Main Window Configuring the HSPICE GUI for Windows Customize configurations using the Configuration menu of the Launcher as shown in Figure 13. The start-up directory defaults to the value of the installdir environment variable set up during HSPICE installation. ■ The input file suffix defaults to .sp. ■ The output file suffix defaults to .lis. ■ The editor defaults to notepad.exe. If you change a value, the Launcher updates the installdir/hspui.cfg file. The next Launcher run provides the new values. The Configuration > Versions item lists current executables and their paths for the Launcher (HSPUI), HSPICE, and WaveView. Note: The Configuration > Version strings change from the main window Versions combo box. You cannot change them here. HSPICE® User Guide: Simulation and Analysis B-2008.09 97 Chapter 6: HSPICE GUI for Windows Configuring the HSPICE GUI for Windows Figure 13 Launcher Options > Open Design To associate your design.sp file with the Launcher, use the File > Associate command in the Windows File Manager. You can double-click an .sp file in the File Manager window to automatically invoke the HSPICE/Win Launcher. Refer to your Windows documentation for details on how to do this. For further configuration tips see Setting the hspui.cfg File Values. Launching Waveview in HSPUI You can activate the WaveView Analyzer add-on through the UI. 1. Open the Versions form in the HSPUI. 98 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 6: HSPICE GUI for Windows Configuring the HSPICE GUI for Windows 2. Configure the sx executable in the Waveview field. 3. Save configuration to hspui.cfg 4. Click the Waveview button in HSPUI main form to launch WaveView Analyzer. HSPICE® User Guide: Simulation and Analysis B-2008.09 99 Chapter 6: HSPICE GUI for Windows Running Multiple Simulations Setting up Windows for Verilog-A The following setup is required to properly compile and simulate Verilog-A models. 1. Select My Computer > Properties > Advanced > Environment Variables 2. Click System Variables. 3. Define a new variable name as “HSP_HOME” and set the value to the actual installation path. For example, C:\synopsys\Hspice_B-2008.09 4. Edit the “PATH” variable to include: %PATH%;%HSP_HOME%\bin;%HSP_HOME%\win2k\veriloga_utils;%HSP_H OME%\win2k\ veriloga_utils\include 5. Click OK to save. Running Multiple Simulations Use the HSPICE/Launcher file browser to build a list of simulations from different directories for consecutive HSPICE processing. Click Multi-jobs in the main window to open the HSPICE Multi-jobs window (Figure 14). Simulation files are chosen from the Drive/Directory list box and placed in the Files list box. 100 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 6: HSPICE GUI for Windows Running Multiple Simulations Figure 14 HSPUI Multi-jobs Window Building the Batch Job List To build a batch job list: 1. Click Multi-jobs in the main window. 2. Using the Drive/Directory boxes, locate the directory of files that you wish to simulate. 3. To load all files in the directory, click the Load button on the right side of the Multi-jobs window. Note that any file names already in the list will be replaced. 4. To add additional files from other directories, repeat Step 2 and use the Append button. HSPICE® User Guide: Simulation and Analysis B-2008.09 101 Chapter 6: HSPICE GUI for Windows Running Multiple Simulations Simulating a Batch Job To simulate a batch job use either of the following two methods: ■ Open the Multi-Jobs window, click Load to load netlists and then click Simulate. or ■ Open the Multi-Jobs window, click Load to load netlists, then click the Save button to create a batch simulation file (*.bat file), then run the *.bat file on Explorer or by using the MS-DOS cmd window. To simulate a batch job list: 1. To simulate all of the files in the Batch Job list, set the pull-down menu to All and click the Simulate button. 2. To run simulation on a single file or a group of files, set the pulldown menu to Selected and select those files you wish to simulate from the Batch Job list box. Use the left mouse button to select a single file. • Press and hold the Ctrl key and select another file with the left mouse button to add to the selected list. • Press and hold the Shift key to select all files between the current file and the last selected file. 3. Click the Simulate button to start the consecutive simulations. Sample Batch Work-Flow Once in Multi-jobs, an example work flow might be: 1. Navigate to your source files: You can select the source drive letter from the pull-down menu in the upper left. Next, if needed, change the file extension filter from .sp to *.* to pick up .hsp or .spi files. Then, you can navigate to a new folder using the file system mini-browser. Note: If you set the filter to *.*, file types other than HSPICE input decks are likely to be included. 2. Add files to the run list using the Load and Append buttons: When you navigate to the folder containing the SPICE decks, they are displayed in the left-hand list window. Although you can select files in this window, clicking 102 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 6: HSPICE GUI for Windows Running Multiple Simulations the Load button adds all the files in the left-hand list window, as well as those in subdirectories. These files go into a run list and are numbered sequentially. Load clears the contents of the run list, but you can navigate to another folder containing HSPICE sources files and click the Append button to add additional files to the run list. 3. Edit the run list: Select files one at a time (CTRL-click) or a range of files (SHIFT-click) and click the Delete button to remove them from the run list. Note: Delete does not remove the file from your hard-drive, just the run list. Clear removes the entire contents of the run list and allows you to start over again. 4. Perform text edits on individual HSPICE jobs: Selecting a job and clicking Edit displays that HSPICE deck in the text editor you designated in the HSPICE UI Configuration > Options dialog. Save and close it to continue. 5. Simulate the jobs: Only selected jobs in the run list can be simulated. Select (highlight) files by clicking on them, or by choosing All Files from the pulldown menu below the Append button. Click Simulate to run the jobs in order, one at a time. 6. Save the run list for later use: Using the File > Save or File > Save As pulldown menu items, you can save the contents of the run list to a file and open it with File > Open to begin work at a later time. 7. Invoke a waveform viewer graphical waveform analysis. 8. Create a batch (*.bat) file with a list of jobs to be run without using the UI: Click the Save button (not File > Save) to create a DOS batch file containing the full path to the HSPICE executable and the design name for each job in the run list. This .bat file can be executed from a DOS command prompt or by double-clicking on it in Windows. Running Multi-Threading To run multi-threading: 1. Select the correct hspice_mt.exe version in the Version combo box. 2. Select the correct number of CPUs in the MultiCpu Option box. 3. Click the Open button to select the input netlist file. 4. Click the Simulate button to start the simulation. HSPICE® User Guide: Simulation and Analysis B-2008.09 103 Chapter 6: HSPICE GUI for Windows Metaencrypt and Converter Utilities, Client/Server Operation Metaencrypt and Converter Utilities, Client/Server Operation For information about use of the metaencrypt utility for encryption of files, refer to Chapter 7, Library and Data Encryption. For information about use of the Converter utility for the conversion of output by HSPICE, refer to Using the HSPICE Output Converter Utility. The C/S mode check boxes allow you to start and use the HSPICE traditional client/server mode. For information about Client/Server usage, refer to Using HSPICE in Client/Server Mode. CMI Directory Structure For information on the Custom Common Model Interface (CMI) directory structure for Windows platforms, contact your Synopsys technical support team to access the application note for the HSPICE CMI. Troubleshooting Guide Setting the hspui.cfg File Values If, for example, your netlists do not have an *.sp suffix, you can edit your hspui.cfg file to accept the file extension that you use. Locate the hspui.cfg file in the HSPICE installation directory. Use this file to configure the HSPUI buttons and settings, including the netlist extension. If you do not find this file, create one as follows. ■ Open the HSPUI. ■ Save the configuration, File > Save Configuration. In the hspui.cfg file you will find a listing similar to the following: 104 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 6: HSPICE GUI for Windows Troubleshooting Guide DesignName= DesignPath= NetSuffix=.sp LisSuffix=.lis HspVersion=C:\synopsys\Hspice_Z-2007.03\BIN\hspice.exe DefEditor=C:\Program Files\Windows NT\Accessories\wordpad.exe DefmCscope= Nproc=1 LastFile(0)= LastFile(1)= LastFile(2)= LastFile(3)= LastFile(4)= The lines for DesignName, DesignPath, HspVersion, and LastFile(#) are informational and should not be edited. ■ To change the netlist extension, edit the NetSuffix line. Multiple file extension support is not available. ■ To change the output listing file to have a different extension, edit the LisSuffix line. ■ To use an editor other than Notepad, enter the path on the DefEditor line. ■ If you want to use CosmosScope as the waveform viewer, add the path to the CosmosScope (cscope.exe) executable on the DefmCscope line. ■ You may also change the default number of processors used when running HSPICE; edit the Nproc line. Text Editor Issues If you click the Edit LL button in the HSPUI, and the listing file (*.lis) comes up with extra carriage returns and is hard to read, solve this issue using one of the following solutions: ■ With Notepad open, click Format on the tool bar and uncheck Word Wrap. ■ Configure the HSPUI to use another text editor to view the files: ■ From the HSPUI click Configuration > Options. ■ For the Default Editor field, click the Browse button. ■ Navigate to the .exe for desired text editor, i.e., C:\Program Files\Windows NT\Accessories\wordpad.exe HSPICE® User Guide: Simulation and Analysis B-2008.09 105 Chapter 6: HSPICE GUI for Windows Troubleshooting Guide Simulating a UNIX Netlist File If the netlist file is a UNIX text file (no ^M at the end of each line), then HSPUI will not read it correctly and the simulate and edit netlist buttons will be grayed out. However, if the file is saved as a DOS text file (^M at the end of each line), then HSPUI will read the file correctly and the simulate and edit netlist buttons are enabled. (HSPICE will simulate a netlist file in either text format.) 106 HSPICE® User Guide: Simulation and Analysis B-2008.09 7 7 Library and Data Encryption Describes the Synopsys library encryption methods and how they are used to protect your intellectual property. Organization These sections present the HSPICE encryption methods according to the following topics: ■ Library Encryption ■ Three Encryption Methods ■ Installing and Running metaencrypt ■ Encryption Guidelines ■ General Example ■ Traditional Library Encryption ■ 8-Byte Key Encryption ■ Triple DES Public and Random Keys ■ Troubleshooting Issues Library Encryption Using HSPICE, you can encrypt your own proprietary HSPICE custom models, parameters, and circuits and distribute to others without revealing your company’s sensitive information. Recipients of an encrypted library can run simulations using HSPICE and your libraries, so that encrypted parameters, encrypted circuit netlists, and internal node voltages do not appear in output HSPICE® User Guide: Simulation and Analysis B-2008.09 107 Chapter 7: Library and Data Encryption Library Encryption files. Your library user sees the devices and circuits as black boxes that provide terminal functions only. Encrypting a Model Library Using the metaencrypt Utility A typical model library from a foundry has the following structure: * model library mylib.lib .lib tt .param toxn= ... .inc mymodel.mdl .endl If you encrypt both mylib.lib and mymodel.mdl, then you will get the error: Command exited with non-zero status 1 during the HSPICE simulation. This is because HSPICE does not support the nesting of encrypted files. To correctly encrypt the model file, you need to change the library structure. The model parameters and the models need to be encrypted separately as shown in the following steps: 1. The modified structure should be as follows: .* model library mylib.lib .lib tt .inc myparam.par \$ put parameter definitions into myparam.par .inc mymodel.mdl \$ original model file .endl 2. Encrypt the parameter file, model file and netlist as follows: metaencrypt -i myparam.par -o myparam.par.enc -t randkey metaencrypt -i mymodel.mdl -o mymodel.mdl.enc -t randkey metaencrypt -i mynetlist.sp -o mynetlist.sp.enc -t randkey 3. To simulate the circuit, include the encrypted files and call the library file, mylib.lib in the top level netlist: 108 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 7: Library and Data Encryption Three Encryption Methods * top level netlist .inc mynetlist.sp.enc .lib mylib.lib tt ... .end * modified library mylib.lib .lib tt .inc myparam.par.enc .inc mymodel.mdl.enc .end Three Encryption Methods HSPICE and HSPICE RF support three types of encryption through the metaencrypt utility: ■ Traditional Library Encryption (Freelib) ■ 8-Byte Key Encryption ■ Triple DES Public and Random Keys The metaencrypt utility can encrypt files with lines up to 254 characters or shorter. You can include multiple types of encrypted files in a HSPICE simulation. Installing and Running metaencrypt This section describes how to install and run metaencrypt. Installing metaencrypt The metaencrypt utility is part of the general HSPICE distribution and is located in the <\$installdir>/bin directory. If you have not installed HSPICE on your system, first install HSPICE according to the Installation Guide and the HSPICE Release Notes. Verify that the license file contains license tokens encrypt and metaencrypt3des for 3DES. HSPICE® User Guide: Simulation and Analysis B-2008.09 109 Chapter 7: Library and Data Encryption Installing and Running metaencrypt Running metaencrypt Syntax metaencrypt -i input_file -o encrypted_output_file \ -t encrypt_type -d encrypt_dir -r synopsys_tool[:access_control] [0|1] -r synopsys_tool[:access_control] [0|1]... Argument Description -i infileName Unencrypted input filename. -o outfileName Encrypted output filename. -t encrypt_type Encryption method: ■ ■ ■ -d encrypt_dir 110 Freelib—weak (low security) -t [ddl1 | ddl2 | custom | freelib] 8-byte—strong (medium security) -t <8-byte-string> Triple DES—strongest (high security) -t [privkey <key or file> | randkey] Valid only when using tripleDES to encrypt file. Data between .PROT and .UNPROT commands are encrypted and written to file infile.enc# in directory encrypt_dir. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 7: Library and Data Encryption Installing and Running metaencrypt Argument Description -r synopsys...tool... synopsys_tool(s) can be: HSPICE, NanoSim, HSIM or Synopsys. access_control can be 0 or 1. The default is 0. 0: tools suppress any warning information related to encrypted block. The default value is ON for all, i.e., if no –r option, or no value specified after –r, it allows all possible for all Synopsys tools (NanoSim, HSIM, HSPICE) to read. 1: Tools do not suppress warning messages from encrypted block. Notes: HSPICE can always read an encrypted netlist file, even if no -r hspice has been specified. If there are multiple settings to same tool, the last setting will be enabled. Example 1: In this invocation, the access_control to NanoSim is 0 while others is 1. .metaencrypt -i test.sp -o test.spe -t randkey + -r synopsys:1 –r nanosim:0 Example 2: Shows how you can limit the parsing of the encrypted files to HSPICE only, not other tools. metaencrypt -i test.sp -o test.spe -t randkey + –r hspice Encryption Guidelines Before encrypting, you must test out any circuits and device parameters, as you will not be able to see what is wrong after encryption because HSPICE does not let you read the encrypted data. You can use any legal HSPICE command inside subcircuits that you encrypt. Refer to Using Subcircuits in Chapter 4, Input Netlist and Data Entry for more information about how to construct subcircuits. The structure of your libraries can affect how you encrypt them. If your library requires that you change the name of a subcircuit, you must encrypt that circuit again. To encrypt more than one file in a directory, use the following shell script, which encrypts the files as a group. In this example, the script uses the traditional encryption method. The script produces a .inc encrypted file, for each .dat file in the current directory. The metaencrypt command assumes that unencrypted files have a .dat suffix. HSPICE® User Guide: Simulation and Analysis B-2008.09 111 Chapter 7: Library and Data Encryption Installing and Running metaencrypt #!/bin/sh for i in *.dat do Base=‘basename \$i .dat‘ metaencrypt -i \$Base.dat -o \$Base.inc -t Freelib done An encrypted file is used in much the same way as before encryption. The name of the file may be different, however, and so the .include and .lib commands may need to be updated. Note: HSPICE encryption does not apply to Verilog-A module files. Instead, you can use the standalone HSPICE Verilog-A compiler, hsp-vacomp, to generate a compiled library file (*.cml) from your Verilog-A module file, then ship the *.cml file instead of your text format Verilog-A file. Note that the *.cml file is both platform- and HSPICE-version specific. For more information, refer to Chapter 31, Using Verilog-A. You can probe any specified encrypted nodes using .OPTION PROBE. General Example The requirements for encrypted libraries of subcircuits are the same as the requirements for regular subcircuit libraries, as described in the HSPICE Simulation and Analysis User Guide. To refer to an encrypted subcircuit, use its subcircuit name in a subcircuit element line of the HSPICE netlist. The following example describes an encrypted I/O buffer library subcircuit. This subcircuit consists of several subcircuits and model commands that you need to protect with encryption. Figure 15 on page 113 shows the organization of subcircuits and models, in the libraries used in this example. 112 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 7: Library and Data Encryption Installing and Running metaencrypt Design View Top Level File System <LibraryDir> Fast iobuf ioinv iobuf.inc <models> Typical ioinv.inc iobuf.inc Slow ioinv.inc ioinv.inc iobuf.inc <models> <models> Figure 15 Encrypted Library Structure The following input file fragment from the main circuit level selects the Fast library. It also creates two instances of the iobuf circuit. ... .Option Search=’<LibraryDir>/Fast’ \$ Corner Spec x1 drvin drvout iobuf Cload=2pF \$ Driver u1 drvout 0 recvin 0 PCBModel ... \$ Trace x2 recvin recvout iobuf \$ Receiver ... The <LibraryDir>/Fast/iobuf.inc file contains: .Subckt iobuf Pin1 Pin2 Cload=1pF * * iobuf.inc - model 2001 improved iobuf * cPin1 Pin1 0 1pF \$ Users cannot change this! x1 Pin1 Pin2 ioinv .Model pMod pmos Level=28 Vto=... \$ <FastModels> .Model nMod nmos Level=28 Vto=... \$ <FastModels> cPin2 Pin2 0 Cload \$ gives you some control .Ends The <LibraryDir>/Fast/ioinv.inc file contains: HSPICE® User Guide: Simulation and Analysis B-2008.09 113 Chapter 7: Library and Data Encryption Installing and Running metaencrypt .Subckt ioinv Pin1 Pin2 mp1 Vcc Pin1 Pin2 Vcc pMod... mn1 Pin2 Pin1 Gnd Gnd nMod... .Ends The encrypted file looks similar to the following: .SUBCKT ioinv Pin1 Pin2 .PROT FREELIB \$ Encryption starts here ... X34%43*27@#^3rx*34&%^#1 ^(*^!^HJHD(*@H\$!:&*\$ dFE2341&*&)(@@3 \$ ... and stops here .ENDS Note: The .UNPROTECT statement is encrypted during the encryption process. After encryption, the basic layout of the subcircuits is the same. However, you cannot read the file. Only HSPICE can read this file. Encryption also suppresses printouts of encrypted model information from HSPICE. Only HSPICE can decrypt the model. Traditional Library Encryption The traditional library encryption algorithm (Freelib) is based on a 5-rotor Enigma machine. You can specify which portions of subcircuits to encrypt. Encrypted portions are designated only within the .PROT/.UNPROT commands. Anything outside is left unencrypted. Library encryption uses a key value, which HSPICE reconstructs for decryption. Note: If you divide a data line into more than one line, and use the line continuation character (+) to link the lines, you cannot add .PROT or .UNPROT commands among these lines. The following example fails: .prot .Model N1 NMOS Level= 57 +TNOM = 27 TOX = 4.5E-09 TSI = .0000001 TBOX = 8E-08 +MOBMOD = 0 CAPMOD = 2 SHMOD =0 .unprot +PARAMCHK=0 WINT = 0 LINT = -2E-08 114 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 7: Library and Data Encryption Installing and Running metaencrypt When metaencrypt reads the input file, it looks for .PROT and .UNPROT pairs, and encrypts the text between them. You can encrypt only one file at a time. Example metaencrypt -i newmos.lib -o newmos.inc -t freelib Note: The netlist needs to be “complete”, i.e,- have an .end statement. Creating Files Using Traditional Encryption The following sections describe: ■ Non-Library Encrypted Portions ■ *.lib File Encryption Non-Library Encrypted Portions You can encrypt the data between .PROT and .UNPROT commands, in a .sp file, so that HSPICE can recognize it. Note: If you use .sp encryption, the encrypted data must not use .INC, .LIB, or .LOAD, to include another file. The following is an example of an .sp file: *sample.sp* ...... .lib 'cmos.lib' TT .prot .... \$ data to be encrypted .... \$ do not include .inc .lib .load in encrypted data .unpr .inc sample2.inc ...... .end *.lib File Encryption You can place any important information into a .lib file, and encrypt it. HSPICE® User Guide: Simulation and Analysis B-2008.09 115 Chapter 7: Library and Data Encryption Example: Traditional (freelib) Encryption in an HSPICE Netlist You can place parallel ..lib commands into one library file, and encrypt each *.lib separately. However, you must place .PROT and .UNPROT commands between each pair of ..lib and .endl commands. Note: You must place .PROT and .UNPROT commands between .lib and .endl commands. To find the library name, HSPICE searches the *.lib file first. The following is an example of a *.lib file: *sample.lib* .lib test1 \$ .prot , .unpr should be put between * .lib and .endl .prot ...... \$ data to be encrypted .unpr ...... \$ data not to be encrypted .end1 test1 .lib test2 \$ .prot , .unpr should be put between * .lib and .end1 .prot ...... \$ data to be encrypted .unpr .end1 test2 .lib test3 ...... \$ data .end1 test3 You use the above encrypted .lib file as you would any unencrypted one. .lib ‘./sample.lib’ test1 .lib ‘./sample.lib’ test2 .lib ‘./sample.lib’ test3 ...... .end Example: Traditional (freelib) Encryption in an HSPICE Netlist The following complete example illustrates the metaencrypt encryption structure. This example enc.sp netlist has three encrypted files: the mm.spe, the xx.ic, and the kk.lib. 116 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 7: Library and Data Encryption Example: Traditional (freelib) Encryption in an HSPICE Netlist file enc.sp: *test .inc .lib .load encryption .inc "mm.spe" .load "xx.ic" .lib ’kk.lib’ pch .OPTION post list .tran 2ns 400ns .end file mm.spe: .prot CUSTOM -hs#ylB]*7[ +t’Y=O\$S[t0]ajL +C :Nx:\$.\$=<*X:\$<#pP=020#ZWP=020x\K:[1:898 y[-x:\$-#tRr0(\$x#4:/[U\$<\K:I[U\$<J <9 :P#ZQ 6%P2V7D6:]4l/0#+:IXj0#ZWP=020#ZWP/[U\$=J++bZ 3[7D6:BxHpg8 /C902P73+26 mh\$y#D:bX/\$\KwI)U-0R#=-ib+\[ a\$o) :P.#\$<) :P.#to)V:\7*K-I1M\$#’;-[Xz:9qpy eMDv0%wUoxZ>mzwF*-(3_;W6x.*P!uW.]a+P0.h:n=O>1q+H(J0 o.H#-/B+(\$;W Me*0x<6#9[UqpH/2h97%;-/B+T35Q \$\m;’_-he[uE\$%H) 5a:ZxRW9x=*77w\$2]=*P!RW%.ahT3VQ H0[I:[ file xx.ic: .prot FREELIB 59yUH\\$=’x.3k77*<]8AT]8 <:7-(:9CV+7x15Xj+h’x=5Xj+(2 +4]8 <:7_D:\[2x9Y>/.7q 59y3\#D\$ *y2k=u]PIq:97jH=u1w5Xj+x6 92k#<2FW0’k772<xBU677Q 59y3\#s# r21\$],29b72[4’/RW72wd#\$:O.U + 0sW%5\$;[4sv;9=zV7[WFW[(g8#/’]=AH%T5:7Z [\$%C999A2P!8 <:X2o60’\$ 06(\$_#upe1:pX8 <5ax/toC n90;<0dw0]23G%C z9\$Dh#Sw5a90 ZM*2!M[0 o729!=PAy73x(/1:6[ + 0%2UT%8 _:-x*\$X+q \$9P2y73x(/1:L T#;*9A27!j+(/z \$\$o#(:/b0 o7ZW-9 -PxJ+y a9[\$0\;n90;<0dw0]23G%C z9\$Dh#Sw5a90 Zr ;6 HSPICE® User Guide: Simulation and Analysis B-2008.09 117 Chapter 7: Library and Data Encryption 8-Byte Key Encryption file kk.lib: .LIB NCH .prot FREELIB HO. T,# %fXz>MZWf*-(3_;w6X.*p!Uw.]A+p0.H:N=o>1Q+h(j0 o.H#-/B+(\$;W Me*0x<6#9[UqpH/2h97%;-/B+T35Q \$\m;’_-he[uE\$%H) 5a:ZxRW9x=*77w\$2]=*P!RW%.ahT3VQ H0[I:[ .ENDL .LIB PCH .prot FREELIB HO. T,#t%fXz>MZWf*-(3_;w6X.*p!Uw.]A+p0.H:N=o>1Q+h(j0 o.H#-/B+(\$;W Me*0x<6#9[UqpH/2h97%;-/B+T35Q \$\m;’_-he[uE\$%H) 5a:ZxRW9x=*77w\$2]=*P!RW%.ahT3VQH0[I:[ .ENDL 8-Byte Key Encryption An 8-byte key encryption feature, based on a 56-bit DES, is available in metaencrypt. When using 8-byte encryption you can encrypt files with line lengths of 254 characters or shorter. The encrypted data is in binary format. To encrypt a file, you provide a keyname that can contain alphabetic characters and numbers, and which is no longer than 8 bytes. To use the encrypted file, you must use the .inc command in the main netlist. HSPICE supports, include file (.inc) encryption, when you use 8-byte key encryption. To use this encryption: 1. Insert the data to encrypt, into an include file. 2. Encrypt this file. Follow these rules when you use 8-byte key encryption: ■ ■ 8-byte encryption does NOT support .LIB, .LOAD, or .OPTION SEARCH encryption. Choose another form of encryption for these types of files. ■ 118 8-byte key encryption supports only .inc encryption. Do not include .PROT and .UNPROT when you perform 8-byte encryption. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 7: Library and Data Encryption 8-Byte Key Encryption ■ If keyname is an 8-byte string (combination of characters and numbers), then metaencrypt performs the 8-byte key encryption. ■ In a .sp file, you cannot encrypt the first line because it is the title. You also cannot encrypt the last line because it marks the end of the file. Creating 8-byte key Encryption Use the following syntax to create 8-byte key encryption: metaencrypt -i example.dat -o example.inc -t fGi85H9b In the following example, example.dat contains the data to encrypt. * DFF subckt netlist \$notice no .prot or .unprot used for this method .subckt XGATE control in n_control out m0 in n_control out vdd pmos l=0.90u w=3.4u m1 in control out gnd nmos l=0.90u w=3.4u .ends ..... v14 vdd gnd dc=5 Xi3 net25 net31 net27 dff_nq DFF l=1u wn=3.8u wp=10u Xi2 dff_nq d_output INV wp=26.4u wn=10.6u .ends XGATE Placing an 8-byte key Encrypted File into a HSPICE Netlist The following fragment is an example of placing an 8-byte key encrypted file into an HSPICE Netlist: * example.sp file using encrypted example.dat .Options Post Brief NoMod .Global vdd gnd .lib 'demo.lib' TT .inc 'example.inc' \$ this is the encrypted file ... * .Tran 1n 8n Sweep Optimize = Opt1 + Result = MaxVout \$ Look at measure + Model = OptMod .end HSPICE® User Guide: Simulation and Analysis B-2008.09 119 Chapter 7: Library and Data Encryption Triple DES Public and Random Keys Triple DES Public and Random Keys When using 3DES technology, the metaencrypt command checks for both the encrypt and metaencrypt3des license tokens. During simulation of a 3DES-encrypted netlist, HSPICE requires a hspice3des license token, for which you must meet export compliance guidelines to use HSPICE 3DES. Check with your local sales representative for this special license. Note: Files encrypted with the Triple DES algorithm cannot be read by previous releases of HSPICE. The HSPICE triple DES encryption uses a 192-bit key to achieve a maximum level of security. You can generate the encryption keys for a new algorithm using one of the following options: ■ 256-bit public key With this option, HSPICE generates a 256-bit public key during the encryption process. You need to distribute this key to the customer in order to run a simulation. The encrypted file and the generated public key is 120 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 7: Library and Data Encryption Triple DES Public and Random Keys different every time the encryption is performed, even with the same private key and input file. This allows you to generate different encrypted file and public key combinations for different customers. Your customers cannot access the key used for encryption, but they can run a simulation on a circuit by putting this public key file in the directory from which the simulation is run. Multiple encrypted files are supported. You have to put all relevant public key files in the directory from which the simulation is run. You can also generate these encrypted files with the same private key or different private keys. The actual “key” needs to be a user-generated 192-bit string. For example, the following two files would be encrypted with the same key: metaencrypt -i a.dat -o a.inc -t <privkey> metaencrypt -i b.dat -o b.inc -t <privkey> Two public key files are created: a.inc.key, and b.inc.key. These files are different even if the same private key is used in the encryption. A simulation run with a netlist file containing .include a.inc and .include b.inc commands requires that both key files be in the simulation directory. ■ 192-bit random key With this option, HSPICE does not need an additional public key. The usage model for this option is consistent with other encryption options in previous releases of HSPICE. The encrypted file is different every time encryption is run. Commands Not Supported by 3DES ■ Embedded .INC encryption, which causes confusion in decryption. ■ The file that you are encrypting cannot contain an .inc, .lib, or .load command that calls another file. Creating 3DES Encrypted Files Observe these rules when creating TripleDES encrypted files: ■ You can use embedded .LIB encryption only if you set it up using .prot and .unprot inside of the .lib plus use the -d option. ■ Do not use .OPTION SEARCH, when you encrypt models and subcircuits. (The old metaencryption functionality supported this method.) To directly encrypt subcircuits and model libraries, use the traditional .INC and .LIB encryption method. HSPICE® User Guide: Simulation and Analysis B-2008.09 121 Chapter 7: Library and Data Encryption Triple DES Public and Random Keys Random Key Example For files without embedded .lib, .inc, or .load commands: metaencrypt -i dff.sp -o dff_rand.spe -t randkey Note: This netlist file has no.prot or .unprot commands in it, similar to 8-byte encryption. For files with embedded .lib commands: metaencrypt -i demo.lib -o demo_rand.lib -t randkey + -d ./lib_rand Note: The demo.lib for this has the same .prot/.unprot setup as for traditional freelib. Public Key Example For files without embedded .lib, .inc, or .load commands: metaencrypt -i dff.sp -o dff_priv.spe -t privkey 0123456789ABCDEF9876543210FEDCBA1357924680ACEBDF Note: This netlist file has no .prot or .unprot commands in it, similar to 8-byte encryption. For a file that has an embedded .lib command: metaencrypt -i demo.lib -o demo_priv.lib -t privkey 0123456789ABCDEF9876543210FEDCBA1357924680ACEBDF -d ./lib_priv Note: The demo.lib for this has the same .prot/.unprot setup as for traditional freelib. Placing 3DES Encryption Files into a HSPICE Netlist While using a random or private key method for tripleDES may look similar, the private one requires that the key be included in the same directory. 122 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 7: Library and Data Encryption Troubleshooting Issues Example 1 Random TripleDES * Example netlist for including random TripleDES .Options Post Brief NoMod .Global vdd gnd .lib 'demo_rand.lib' TT \$ bring in the random 3DES lib file, *that looks at the ./lib_rand directory for files .inc 'dff_rand.spe' \$ bring in random 3DES encrypted design *file .... .end Example 2 Private TripleDES * Example netlist for including private TripleDES .Options Post Brief NoMod .Global vdd gnd .lib 'demo_priv.lib' TT \$ bring in private key lib file; the *keys are in the ./lib_priv directory along with the files .inc 'dff_priv.spe' \$ bring in private key encrypted file; *key must be in this same directory (dff_priv.spe.key) ..... .end Troubleshooting Issues ‘Bad encryption format’ or ‘version check failed’ error If you receive new encrypted models from a vendor and are getting a “Bad encryption format’ or “version check failed” error, your models were encrypted with the Triple DES (3DES) encryption technology. Because of export restrictions on the strong encryption technology, a separate license is required. To verify, view the HSPICE listing file to see a failed license checkout attempt: lic: Unable to checkout hspice3des lic: lic: Release hspice3des token(s) lic: feature hspice3des not found 3DES licenses are provided at no charge. Have your site contact call your Synopsys sales representative and request that they add a \$0 triple DES line item, part #4279 to your existing PO. The number of 3DES licenses requested should equal the number of simulations (up to the quantity of HSPICE licenses you own) that you simultaneously simulate using triple DES encrypted models. HSPICE® User Guide: Simulation and Analysis B-2008.09 123 Chapter 7: Library and Data Encryption Troubleshooting Issues **warning** parameters... as an expression containing output signals This warning occurs even when there are no explicit encrypted blocks in the netlist. There are two reasons for this warning message. ■ .protect and .unprotect commands are in the netlist. ■ The results of parameter expressions which contain output signals are not correct. For example: .param myfunc (one,two)='abs (one - two)' .param test=myfunc(v(1),v(2)) .protect .if ( test <= 1 ) .param k='2*1p' .elseif ( test <= 4 ) .param k='8*1p' .else .param k='1*test*1p' .endif .unprotect c1 2 0 c=k 124 HSPICE® User Guide: Simulation and Analysis B-2008.09 Part: 2 Elements and Devices The following chapters/topics are included in this Part: ■ Chapter 8, Elements ■ Chapter 9, Sources and Stimuli ■ Chapter 10, Parameters and Functions ■ Chapter 11, Simulation Output HSPICE® User Guide: Simulation and Analysis B-2008.09 125 126 HSPICE® User Guide: Simulation and Analysis B-2008.09 8 Elements 8 Describes the syntax for the basic elements of a circuit netlist in HSPICE or HSPICE RF. Elements are local and sometimes customized instances of a device model specified in your design netlist. Element names can be up to 1024 characters. For descriptions of the standard device models on which elements (instances) are based, see the HSPICE Reference Manual: Elements and Device Models and the HSPICE Reference Manual: MOSFET Models. For signal integrity applications see the HSPICE User Guide: Signal Integrity. These topics are covered in the following sections: ■ Passive Elements ■ Multi-Terminal Linear Elements ■ Active Elements ■ IBIS Buffers (HSPICE Only) Passive Elements This section describes the passive elements: resistors, capacitors, and inductors. See Multi-Terminal Linear Elements for discussion of the W-, U-, and S-elements. See also, T-element (Ideal Transmission Lines) in the HSPICE User Guide: Signal Integrity. The content of this section includes: ■ Values for Elements ■ Resistor Elements in a HSPICE or HSPICE RF Netlist ■ Linear Resistors HSPICE® User Guide: Simulation and Analysis B-2008.09 127 Chapter 8: Elements Passive Elements ■ Behavioral Resistors in HSPICE or HSPICE RF ■ Frequency-Dependent Resistors ■ Skin Effect Resistors ■ Capacitors ■ Linear Resistors ■ Frequency-Dependent Capacitors ■ Behavioral Resistors in HSPICE or HSPICE RF ■ DC Block Capacitors ■ Charge-Conserved Capacitors ■ Inductors ■ Mutual Inductors ■ Ideal Transformer ■ Linear Inductors ■ Frequency-Dependent Inductors ■ AC Choke Inductors ■ Reluctors Values for Elements HSPICE RF accepts equation-based resistors and capacitors. You can specify the value of a resistor or capacitor as an arbitrary equation, involving node voltages or variable parameters. Unlike HSPICE, you cannot use parameters to indirectly reference node voltages in HSPICE RF. Resistor Elements in a HSPICE or HSPICE RF Netlist Rxxx n1 n2 <mname> Rval [TC1 TC2 TC3] [SCALE=val] [M=val] + [AC=val] [DTEMP=val] [L=val] [W=val] [C=val] + [NOISE=val] Rxxx n1 n2 mname [R=>resistance TC1=val + [<TC2=>val] [<TC=>val] [SCALE=val] [M=val] + [AC=val> [DTEMP=val> [L=val] [W=val] + [C=val] [NOISE=val] 128 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 8: Elements Passive Elements Rxxx n1 n2 R=‘equation’ … Parameter Description Rxxx Resistor element name. Must begin with R, followed by up to 1023 alphanumeric characters. n1 Positive terminal node name. n2 Negative terminal node name. mname Resistor model name. Use this name in elements, to reference a resistor model. TC TC1 alias. The current definition overrides the previous definition. TC1 First-order temperature coefficient for the resistor. See the Passive Device Models chapter in the HSPICE Elements and Device Models Manual for temperature-dependent relations. TC2 Second-order temperature coefficient for the resistor. SCALE Element scale factor; scales resistance and capacitance by its value. Default=1.0. R= resistance Resistance value at room temperature. This can be: ■ ■ ■ ■ ■ a numeric value in ohms a parameter in ohms a function of any node voltages a function of branch currents any independent variables such as time, hertz, and temper M Multiplier to simulate parallel resistors. For example, for two parallel instances of a resistor, set M=2, to multiply the number of resistors by 2. Default=1.0. AC Resistance for AC analysis. Default=Reff. DTEMP Temperature difference between the element and the circuit, in degrees Celsius. Default=0.0. L Resistor length in meters. Default=0.0, if you did not specify L in a resistor model. HSPICE® User Guide: Simulation and Analysis B-2008.09 129 Chapter 8: Elements Passive Elements Parameter Description W Resistor width. Default=0.0, if you did not specify W in the model. C Capacitance connected from node n2 to bulk. Default=0.0, if you did not specify C in a resistor model user-defined Can be a function of any node voltages, element currents, temperature, equation frequency, or time NOISE ■ ■ NOISE=0, do not evaluate resistor noise. NOISE=1, evaluate resistor noise (default). Resistance can be a value (in units of ohms) or an equation. Required parameters are the two nodes, and the resistance or model name. If you specify other parameters, the node and model name must precede those parameters. Other parameters can follow in any order. If you specify a resistor model (see the Passive Device Models chapter in the HSPICE Elements and Device Models Manual), the resistance value is optional. HSPICE Examples In the following example, the R1 resistor connects from the Rnode1 node to the Rnode2 node, with a resistance of 100 ohms. R1 Rnode1 Rnode2 100 The RC1 resistor connects from node 12 to node 17, with a resistance of 1 kilohm, and temperature coefficients of 0.001 and 0. RC1 12 17 R=1k TC1=0.001 TC2=0 The Rterm resistor connects from the input node to ground, with a resistance determined by the square root of the analysis frequency (non-zero for AC analysis only). Rterm input gnd R=’sqrt(HERTZ)’ The Rxxx resistor connects from node 98999999 to node 87654321 with a resistance of 1 ohm for DC and time-domain analyses, and 10 gigohms for AC analyses. Rxxx 98999999 87654321 1 AC=1e10 HSPICE RF Examples Some basic examples for HSPICE RF include: 130 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 8: Elements Passive Elements ■ R1 is a resistor whose resistance follows the voltage at node c. R1 1 0 ‘v(c)’ ■ R2 is a resistor whose resistance is the sum of the absolute values of nodes c and d. R2 1 0 ‘abs(v(c)) + abs(v(d))’ ■ R3 is a resistor whose resistance is the sum of the rconst parameter, and 100 times tx1 for a total of 1100 ohms. .PARAM rconst=100 tx1=10 R3 4 5 ‘rconst + tx1 * 100’ Linear Resistors Rxxx node1 node2 modelname [R =] value [TC1=val] + [TC2=val] [W=val] [L=val] [M=val] + [C=val] [DTEMP=val] [SCALE=val] Parameter Description Rxxx Name of a resistor node1 and node2 Names or numbers of the connecting nodes modelname Name of the resistor model value Nominal resistance value, in ohms R Resistance, in ohms, at room temperature TC1, TC2 Temperature coefficient W Resistor width L Resistor length M Parallel multiplier C Parasitic capacitance between node2 and the substrate DTEMP Temperature difference between element and circuit SCALE Scaling factor HSPICE® User Guide: Simulation and Analysis B-2008.09 131 Chapter 8: Elements Passive Elements Example R1 1 2 10.0 Rload 1 GND RVAL .param rx=100 R3 2 3 RX TC1=0.001 TC2=0 RP X1.A X2.X5.B .5 .MODEL RVAL R In the example above, R1 is a simple 10Ω linear resistor and Rload calls a resistor model named RVAL, which is defined later in the netlist. Note: If a resistor calls a model, then you do not need to specify a constant resistance, as you do with R1. ■ R3 takes its value from the RX parameter, and uses the TC1 and TC2 temperature coefficients, which become 0.001 and 0, respectively. ■ RP spans across different circuit hierarchies, and is 0.5Ω. Behavioral Resistors in HSPICE or HSPICE RF Rxxx n1 n2 . . . [R=] ‘equation’ . . . Note: The equation can be a function of any node voltage or branch current, and any independent variables such as time, hertz, or temper. Example R1 A B R=‘V(A) + I(VDD)’ Frequency-Dependent Resistors Rxxx n1 n2 R=equation [CONVOLUTION=[0|1|2]] [FBASE=value] 132 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 8: Elements Passive Elements + <FMAX=value>> Parameter CONVOLUTION Description Indicates which method is used. ■ ■ ■ FBASE 0: Acts the same as the conventional method. This is the default. 1 : Applies recursive convolution, and if the rational function is not accurate enough, it switches to linear convolution. 2 : Applies linear convolution. Specifies the lower bound of the transient analysis frequency. For CONVOLUTION=1 mode, HSPICE starts sampling at this frequency. For CONVOLUTION=2 mode, HSPICE uses this value as the base frequency point for Inverse Fourier Transformation. For recursive convolution, the default value is 0Hz, and for linear convolution, HSPICE uses the reciprocal of the transient period. FMAX Specifies the possible maximum frequency of interest. The default value is the frequency point where the function reaches close enough to infinity value, assuming that the monotonous function is approaching the infinity value and that it is taken at 10THz. The equation should be a function of HERTZ. If CONVOLUTION is turned on when a HERTZ keyword is not used in the equation, it is automatically be turned off to let the resistor behave as conventional.The equation can be a function of temperature, but it cannot be node voltage or branch current and time. The equation can only be a function of time-independent variables such as hertz, and temperature. Example R1 1 2 r='1.0 + 1e-5*sqrt(HERTZ)' CONVOLUTION=1 Skin Effect Resistors Rxxx n1 n2 R=value Rs=value The Rs indicates the skin effect coefficient of the resistor. HSPICE® User Guide: Simulation and Analysis B-2008.09 133 Chapter 8: Elements Passive Elements The complex impedance of the resistor can be expressed as the following equation: R(f)=Ro + (1+j)*Rs*sqrt(f) The Ro, j, and f are DC resistance, imaginably unit (j^2=-1) and frequency, respectively. Capacitors Cxxx n1 n2 <mname> <C=>capacitance <<TC1=>val> + <<TC2=>val> <SCALE=val> <IC=val> <M=val> + <W=val> <L=val> <DTEMP=val> Cxxx n1 n2 <C=>’equation’ <CTYPE=0|1> + <above_options...> Polynomial form: Cxxx n1 n2 POLY c0 c1... <IC=val> <M=val> Parameter Cxxx Capacitor element name. Must begin with C, followed by up to 1023 alphanumeric characters. n1 Positive terminal node name. n2 Negative terminal node name. mname Capacitance model name. Elements use this name to reference a capacitor. C=capacitance Capacitance at room temperature—a numeric value or a parameter in farads. TC1 First-order temperature coefficient for the capacitor. See the Passive Device Models chapter in the HSPICE Elements and Device Models Manual for temperature-dependent relations. TC2 Second-order temperature coefficient for the capacitor. SCALE 134 Description Element scale parameter, scales capacitance by its value. Default=1.0. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 8: Elements Passive Elements Parameter Description IC Initial voltage across the capacitor, in volts. If you specify UIC in the .TRAN statement, HSPICE or HSPICE RF uses this value as the DC operating point voltage. The .IC statement overrides it. M Multiplier, used to simulate multiple parallel capacitors. Default=1.0 W Capacitor width, in meters. Default=0.0, if you did not specify W in a capacitor model. L Capacitor length, in meters. Default=0.0, if you did not specify L in a capacitor model. DTEMP Element temperature difference from the circuit temperature, in degrees Celsius. Default=0.0. C=’equation’ Capacitance at room temperature, specified as a function of ■ ■ ■ any node voltages any branch currents any independent variables such as time, hertz, and temper CTYPE Determines capacitance charge calculation for elements with capacitance equations. If the C capacitance is a function of V(n1<,n2>), set CTYPE=0. Use this setting correctly, to ensure proper capacitance calculations, and correct simulation results. Default=0. POLY Keyword, to specify capacitance as a non-linear polynomial. c0 c1... Coefficients of a polynomial, described as a function of the voltage across the capacitor. c0 represents the magnitude of the 0th order term, c1 represents the magnitude of the 1st order term, and so on. You cannot use parameters as coefficient values. You can specify capacitance as a numeric value, in units of farads, as an equation, or as a polynomial of the voltage. The only required fields are the two nodes, and the capacitance or model name. ■ If you use the parameter labels, the nodes and model name must precede the labels. Other arguments can follow in any order. ■ If you specify a capacitor model (see the Passive Device Models chapter in the HSPICE Elements and Device Models Manual), the capacitance value is optional. HSPICE® User Guide: Simulation and Analysis B-2008.09 135 Chapter 8: Elements Passive Elements If you use an equation to specify capacitance, the CTYPE parameter determines how HSPICE calculates the capacitance charge. The calculation is different, depending on whether the equation uses a self-referential voltage (that is, the voltage across the capacitor, whose capacitance is determined by the equation). To avoid syntax conflicts, if a capacitor model has the same name as a capacitance parameter, HSPICE or HSPICE RF uses the model name. Example 1 In the following example, C1 assumes its capacitance value from the model, not the parameter. .PARAMETER CAPXX=1 C1 1 2 CAPXX .MODEL CAPXX C CAP=1 Example 2 In the following example, the C1 capacitors connect from node 1 to node 2, with a capacitance of 20 picofarads: C1 1 2 20p In this next example, Cshunt refers to three capacitors in parallel, connected from the node output to ground, each with a capacitance of 100 femtofarads. Cshunt output gnd C=100f M=3 The Cload capacitor connects from the driver node to the output node. The capacitance is determined by the voltage on the capcontrol node, times 1E-6. The initial voltage across the capacitor is 0 volts. Cload driver output C=’1u*v(capcontrol)’ CTYPE=1 IC=0v The C99 capacitor connects from the in node to the out node. The capacitance is determined by the polynomial C=c0 + c1*v + c2*v*v, where v is the voltage across the capacitor. C99 in out POLY 2.0 0.5 0.01 Linear Capacitors Cxxx node1 node2 < modelname > < C=> value < TC1=val > + < TC2=val > <W=val > < L=val > < DTEMP=val > 136 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 8: Elements Passive Elements + < M=val > < SCALE=val > < IC=val > Parameter Description Cxxx Name of a capacitor. Must begin with C, followed by up to 1023 alphanumeric characters. node1 and node2 Names or numbers of connecting nodes. value Nominal capacitance value, in Farads. modelname Name of the capacitor model. C Capacitance, in Farads, at room temperature. TC1, TC2 Specifies the temperature coefficient. W Capacitor width. L Capacitor length. M Multiplier to simulate multiple parallel capacitors. DTEMP Temperature difference between element and circuit. SCALE Scaling factor. IC Initial capacitor voltage. Example Cbypass 1 0 10PF C1 2 3 CBX .MODEL CBX C CB B 0 10P IC=4V CP X1.XA.1 0 0.1P In this example: ■ Cbypass is a straightforward, 10-picofarad (PF) capacitor. ■ C1, which calls the CBX model, does not have a constant capacitance. ■ CB is a 10 PF capacitor, with an initial voltage of 4V across it. ■ CP is a 0.1 PF capacitor. HSPICE® User Guide: Simulation and Analysis B-2008.09 137 Chapter 8: Elements Passive Elements Frequency-Dependent Capacitors You can specify frequency-dependent capacitors using the C=’equation’ with the HERTZ keyword. The HERTZ keyword represents the operating frequency. In time domain analyses, an expression with the HERTZ keyword behaves differently according to the value assigned to the CONVOLUTION keyword. Syntax Cxxx n1 n2 C=’equation’ <CONVOLUTION=[0|1|2] + <FBASE=val> <FMAX=val>> Parameter Description n1 n2 Names or numbers of connecting nodes. equation Expressed as a function of HERTZ. If CONVOLUTION=1 or 2 and HERTZ is not used in the equation, CONVOLUTION is turned off and the capacitor behaves conventionally. The equation can be a function of temperature, but it does not support variables of node voltage, branch current, or time. If these variables exist in the expression and CONVOLUTION=1 or 2, then only their values at the operating point are considered in calculation. CONVOLUTION Specifies the method used. ■ ■ 0 (default): HERTZ=0 in time domain analysis. 1 or 2: performs Inverse Fast Fourier Transformation (IFFT) linear convolution. FBASE Base frequency to use for transient analysis. This value becomes the base frequency point for Inverse Fast Fourier Transformation (IFFT) when CONVOLUTION=1 or 2. If you do not set this value, the base frequency is a reciprocal value of the transient period. FMAX Maximum frequency to use for transient analysis. Used as the maximum frequency point for Inverse Fourier Transformation. If you do not set this value, the reciprocal value of RISETIME is taken. Example C1 1 2 C='1e-6 - HERTZ/1e16' CONVOLUTION=1 fbase=10 + fmax=30meg 138 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 8: Elements Passive Elements Behavioral Capacitors in HSPICE or HSPICE RF Cxxx n1 n2 . . . C=‘equation’ CTYPE=0 or 1 Parameter Description CTYPE Determines the calculation mode for elements that use capacitance equations. Set this parameter carefully, to ensure correct simulation results. HSPICE RF extends the definition and values of CTYPE, relative to HSPICE: ■ ■ ■ CTYPE=0, if C depends only on its own terminal voltages—that is, a function of V(n1<, n2>). CTYPE=1, if C depends only on outside voltages or currents. CTYPE=2, if C depends on both its own terminal and outside voltages. This is the default for HSPICE RF. HSPICE does not support CTYPE=2. You can specify the capacitor value as a function of any node voltage or branch current, and any independent variables such as time, hertz, and temper. Example C1 1 0 C=’1e-9*V(10)’ CTYPE=1 V10 10 0 PWL(0,1v t1,1v t2,4v) DC Block Capacitors Cxxx node1 node2 <C=> INFINITY <IC=val> When the capacitance of a capacitor is infinity, this element is called a “DC block.” In HSPICE, you specify an INFINITY value for such capacitors. HPSICE does not support any other capacitor parameters for DC block elements because HSPICE assumes that an infinite capacitor value is independent of any scaling factors. The DC block acts as an open circuit for all DC analyses. HSPICE calculates the DC voltage across the nodes of the circuit. In all other (non-DC) analyses, a DC voltage source of this value represents the DC block—HSPICE does not allow dv/dt variations. Charge-Conserved Capacitors Cxxx node1 node2 q=’expression’ HSPICE supports AC, DC, TRAN, and PZ analyses for charge-conserved capacitors. HSPICE® User Guide: Simulation and Analysis B-2008.09 139 Chapter 8: Elements Passive Elements The expression supports the following parameters and variables: ■ Parameters • • ■ node voltages branch currents Variables • time • temper • hertz Note: The hertz variable is not supported in transient analyses. Parameters must be used directly in an equation. HSPICE does not support parameters that represent an equation containing variables. Error Handling If you use an unsupported parameter in an expression, HSPICE issues an error message and aborts the simulation. HSPICE ignores unsupported analysis types and then issues warning a message. Limitations capacitors: The following syntax does not support charge-conserving Cxx node1 node2 C=’expression’ Capacitor equations are not implicitly converted to charge equations. Example 1: Capacitance-based Capacitor C1 a b C=‘Co*(1+alpha*V(a,b)’ ctype=0 You can obtain Q by integrating ‘C’ w.r.t V(a,b) Example 2: Charge-based Capacitor C1 a b Q=‘Co*V(a,b)(1+0.5*alpha*V(a,b)) 140 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 8: Elements Passive Elements Example 3: Capacitance-based Capacitor .option list node post r1 1 2 100 r2 3 0 200 Vin 1 0 pulse(0 5v 1ns 2ns 2ns 10ns 20ns) C1 2 3 c='cos(v(2,3)) + v(1,2)’ ctype=2 .tran 1ns 100ns .print tran i(c1) .end Example 4: Charge-based Capacitor .option list node post r1 1 2 100 r2 3 0 200 Vin 1 0 pulse(0 5v 1ns 2ns 2ns 10ns 20ns) C1 2 3 q='sin(v(2,3)) + v(2,3)*v(1,2)' .tran 1ns 100ns .print tran i(c1) .end Inductors General form: Lxxx n1 n2 <L=>inductance <<TC1=>val> + <<TC2=>val> <SCALE=val> <IC=val> <M=val> + <DTEMP=val> <R=val> Lxxx n1 n2 L=‘equation’ <LTYPE=val> <above_options...> Polynomial form: Lxxx n1 n2 POLY c0 c1... <above_options...> Magnetic winding form: Lxxx n1 n2 NT=turns <above_options...> Parameter Description Lxxx Inductor element name. Must begin with L, followed by up to 1023 alphanumeric characters. n1 Positive terminal node name. n2 Negative terminal node name. HSPICE® User Guide: Simulation and Analysis B-2008.09 141 Chapter 8: Elements Passive Elements Parameter Description TC1 First-order temperature coefficient for the inductor. See the Passive Device Models chapter in the HSPICE Elements and Device Models Manual for temperature-dependent relations. TC2 Second-order temperature coefficient for the inductor. SCALE Element scale parameter; scales inductance by its value. Default=1.0. IC Initial current through the inductor, in amperes. HSPICE or HSPICE RF uses this value as the DC operating point current. L=inductance Inductance value. This can be: ■ ■ ■ ■ ■ a numeric value, in henries a parameter in henries a function of any node voltages a function of branch currents any independent variables such as time, hertz, and temper M Multiplier, used to simulate parallel inductors. Default=1.0. DTEMP Temperature difference between the element and the circuit, in degrees Celsius. Default=0.0. R Resistance of the inductor, in ohms. Default=0.0. L=‘equation’ Inductance at room temperature, specified as: ■ ■ ■ a function of any node voltages a function of branch currents any independent variables such as time, hertz, and temper LTYPE POLY 142 Calculates inductance flux for elements, using inductance equations. If the L inductance is a function of I(Lxxx), then set LTYPE=0. Otherwise, set LTYPE=1. Use this setting correctly, to ensure proper inductance calculations, and correct simulation results. Default=0. Keyword that specifies the inductance, calculated by a polynomial. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 8: Elements Passive Elements Parameter Description c0 c1... Coefficients of a polynomial in the current, describing the inductor value. c0 is the magnitude of the 0th order term, c1 is the magnitude of the 1st order term, and so on. NT=turns Number of turns of an inductive magnetic winding. In this syntax, the inductance can be either a value (in units of henries), an equation, a polynomial of the current, or a magnetic winding. Required fields are the two nodes, and the inductance or model name. ■ If you specify parameters, the nodes and model name must be first. Other parameters can be in any order. ■ If you specify an inductor model (see the Passive Device Models chapter in the HSPICE Elements and Device Models Manual), the inductance value is optional. Example 1 In the following example, the L1 inductor connects from the coilin node to the coilout node, with an inductance of 100 nanohenries. L1 coilin coilout 100n Example 2 The Lloop inductor connects from node 12 to node 17. Its inductance is 1 microhenry, and its temperature coefficients are 0.001 and 0. Lloop 12 17 L=1u TC1=0.001 TC2=0 Example 3 The Lcoil inductor connects from the input node to ground. Its inductance is determined by the product of the current through the inductor, and 1E-6. Lcoil input gnd L=’1u*i(input)’ LTYPE=0 Example 4 The L99 inductor connects from the in node to the out node. Its inductance is determined by the polynomial L=c0 + c1*i + c2*i*i, where i is the current through the inductor. The inductor also has a specified DC resistance of 10 ohms. L99 in out POLY 4.0 0.35 0.01 R=10 HSPICE® User Guide: Simulation and Analysis B-2008.09 143 Chapter 8: Elements Passive Elements Example 5 The L inductor connects from node 1 to node, as a magnetic winding element, with 10 turns of wire. L 1 2 NT=10 Mutual Inductors General form: Kxxx Lyyy Lzzz <K=coupling | coupling> Mutual core form: Kaaa Lbbb <Lccc ... <Lddd>> mname <MAG=magnetization> Parameter Kxxx Mutual inductor element name. Must begin with K, followed by up to 1023 alphanumeric characters. Lyyy Name of the first of two coupled inductors. Lzzz Name of the second of two coupled inductors. K=coupling Coefficient of mutual coupling. K is a unitless number, with magnitude > 0. If K is negative, the direction of coupling reverses. This is equivalent to reversing the polarity of either of the coupled inductors. Use the K=coupling syntax when using a parameter value or an equation, and the keyword “k=” can be omitted. Kaaa Saturable core element name. Must begin with K, followed by up to 1023 alphanumeric characters. Lbbb, Lccc, Lddd Names of the windings about the Kaaa core. One winding element is required, and each winding element must use the magnetic winding syntax. All winding elements with the same magnetic core model should be written in one mutual inductor statement in the netlist. mname 144 Description Saturable core model name. (See the Passive Device Models chapter in the HSPICE Elements and Device Models Manual for more information.) HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 8: Elements Passive Elements Parameter Description MAG= Initial magnetization of the saturable core. You can set this to +1, 0, or -1, where +/- 1 refer to positive and negative values of the BS model parameter. (See the Passive Device Models chapter in the HSPICE Elements and Device Models Manual for more information.) magnetization In this syntax, coupling is a unitless value from zero upward, representing the coupling strength. If you use parameter labels, the nodes and model name must be first. Other arguments can be in any order. If you specify an inductor model (see the Passive Device Models chapter in the HSPICE Elements and Device Models Manual), the inductance value is optional. You can determine the coupling coefficient, based on geometric and spatial information. To determine the final coupling inductance, HSPICE or HSPICE RF divides the coupling coefficient by the square-root of the product of the selfinductances. When using the mutual inductor element to calculate the coupling between more than two inductors, HSPICE or HSPICE RF can automatically calculate an approximate second-order coupling. See the third example for a specific situation. Note: The automatic inductance calculation is an estimation, and is accurate for a subset of geometries. The second-order coupling coefficient is the product of the two first-order coefficients, which is not correct for many geometries. Example 1 The Lin and Lout inductors are coupled, with a coefficient of 0.9. K1 Lin Lout 0.9 Example 2 The Lhigh and Llow inductors are coupled, with a coefficient equal to the value of the COUPLE parameter. Kxfmr Lhigh Llow K=COUPLE ■ The K1 mutual inductor couples L1 and L2. ■ The K2 mutual inductor couples L2 and L3. HSPICE® User Guide: Simulation and Analysis B-2008.09 145 Chapter 8: Elements Passive Elements Example 3 The coupling coefficients are 0.98 and 0.87. HSPICE or HSPICE RF automatically calculates the mutual inductance between L1 and L3, with a coefficient of 0.98*0.87=0.853. K1 L1 L2 0.98 K2 L2 L3 0.87 Ideal Transformer Kxxx Li Lj <k=IDEAL | IDEAL> Ideal transformers use the IDEAL keyword with the K element to designate ideal K transformer coupling. This keyword activates the following equation set for non-DC values, which is presented here with multiple coupled inductors. Ij is the current into the first terminal of Lj. V1/sqrt(L1)=V2/sqrt(L2)=V3/sqrt(L3)=V4/sqrt(L4)=... (I1*sqrt(L1) + (I2*sqrt(L2) + (I3*sqrt(L3) + (I4*sqrt(L4) + ...=0 HSPICE can solve any I or V in terms of L ratios. DC is treated as expected— inductors are treated as short circuits. Mutual coupling is ignored for DC. Inductors that use the INFINITY keyword can be coupled with IDEAL K elements. In this situation, all inductors involved must have the INFINITY value, and for K=IDEAL, the ratio of all L values is unity. Then, for two L values: v2= v1 i2 + i1=0 Example 1 This example is a standard 5-pin ideal balun transformer subcircuit. Two pins are grounded for standard operation. With all K values being IDEAL, the absolute L values are not crucial—only their ratios are important. 146 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 8: Elements Passive Elements ** ** all K's ideal ** ** o----in** Lin=1 ** 0 o------** .subckt BALUN1 in Lin in gnd Lo1 out1 gnd Lo2 gnd out2 K12 Lin Lo1 K13 Lin Lo2 K23 Lo1 Lo2 .ends -----o out1 Lo1=.25 -----o 0 Lo2=.25 -----o out2 out1 out2 L=1 L=0.25 L=0.25 IDEAL IDEAL IDEAL Example 2 This example is a 2-pin ideal 4:1 step-up balun transformer subcircuit with shared DC path (no DC isolation). Input and output have a common pin, and both inductors have the same value. Note that Rload=4*Rin. ** ** all K's ideal **in o-------------------o out=in ** L1=1 ** -----o 0 ** L2=1 ** -----o out2 ** ** With all K's ideal, the actual L's values are ** not important -- only their ratio to each other. .subckt BALUN2 in out2 L1 in gnd L=1 L2 gnd out2 L=1 K12 L1 L2 IDEAL .ends Example 3 This example is a 3-pin ideal balun transformer with shared DC path (no DC isolation). All inductors have the same value (here set to unity). HSPICE® User Guide: Simulation and Analysis B-2008.09 147 Chapter 8: Elements Passive Elements ** ** all K's ideal -----o out1 ** Lo2=1 ** -----o 0 ** Lo1=1 ** -----o out2 ** in Lin=1 ** o-------------------o in ** .subckt BALUN3 in out1 out2 Lo2 gnd out1 L=1 Lo1 out2 gnd L=1 Lin in out2 L=1 K12 Lin Lo1 IDEAL K13 Lin Lo2 IDEAL K23 Lo1 Lo2 IDEAL .ends Linear Inductors Lxxx node1 node2 <L => inductance <TC1=val> <TC2=val> + <M=val> <DTEMP=val> <IC=val> Parameter Description Lxxx Name of an inductor. node1 and node2 Names or numbers of the connecting nodes. inductance Nominal inductance value, in Henries. L Inductance, in Henries, at room temperature. TC1, TC2 Temperature coefficient. M Multiplier for parallel inductors. DTEMP Temperature difference between the element and the circuit. IC Initial inductor current. Example: LX A B 1E-9 LR 1 0 1u IC=10mA 148 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 8: Elements Passive Elements ■ LX is a 1 nH inductor. ■ LR is a 1 uH inductor, with an initial current of 10 mA. Frequency-Dependent Inductors You can specify frequency-dependent inductors using the L=’equation’ with the HERTZ keyword. The HERTZ keyword represents the operating frequency. In time domain analyses, an expression with the HERTZ keyword behaves differently according to the value assigned to the CONVOLUTION keyword. Syntax Lxxx n1 n2 L=’equation’ <CONVOLUTION=[0|1|2] <FBASE=value> + <FMAX=value>> Parameter Description Lxxx Inductor element name. Must begin with L, followed by up to 1023 alphanumeric characters n1 n2 Positive and negative terminal node names. equation The equation should be a function of HERTZ. If CONVOLUTION is turned on when a HERTZ keyword is not used in the equation, CONVOLUTION is automatically be turned off and the inductor behaves conventionally.The equation can be a function of temperature, but it does not support variables of node voltage, branch current, or time. If these variables exist in the equation with CONVOLUTION turned on, only their values at the operating point are considered in the calculation. CONVOLUTION Indicates which method is used. ■ ■ ■ 0 (default): Acts the same as the conventional method. 1 : Applies recursive convolution, and if the rational function is not accurate enough, it switches to linear convolution. 2 : Applies linear convolution. HSPICE® User Guide: Simulation and Analysis B-2008.09 149 Chapter 8: Elements Passive Elements Parameter Description FBASE Specifies the lower bound of the transient analysis frequency. ■ ■ ■ ■ FMAX For CONVOLUTION=1 mode, HSPICE starts sampling at this frequency. For CONVOLUTION=2 mode, HSPICE uses this value as the base frequency point for Inverse Fourier Transformation. For recursive convolution, the default value is 0Hz. For linear convolution, HSPICE uses the reciprocal of the transient period. Specifies the possible maximum frequency of interest. The default value is the frequency point where the function reaches close enough to infinity value, assuming that the monotonous function is approaching the infinity value and that it is taken at 10THz. Example L1 1 2 L='0.5n + 0.5n/(1 + HERTZ/1e8)' CONVOLUTION=1 fbase=10 + fmax=30meg AC Choke Inductors Syntax Lxxx node1 node2 <L=> INFINITY <IC=val> When the inductance of an inductor is infinity, this element is called an “AC choke.” In HSPICE, you specify an INFINITY value for inductors. HSPICE does not support any other inductor parameters because it assumes that the infinite inductance value is independent of temperature and scaling factors. The AC choke acts as a short circuit for all DC analyses and HSPICE calculates the DC current through the inductor. In all other (non-DC) analyses, a DC current source of this value represents the choke—HSPICE does not allow di/dt variations. Reluctors Syntax Reluctance Inline Form Lxxx n1p n1n ... nNp nNn + RELUCTANCE=(r1, c1, val1, r2, c2, val2, ... , rm, cm, valm) + <SHORTALL=yes | no> <IGNORE_COUPLING=yes | no> 150 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 8: Elements Passive Elements Reluctance External File Form Lxxx n1p n1n ... nNp nNn RELUCTANCE + FILE=”<filename1>” [FILE=”<filename2>” [...]] + <SHORTALL=yes | no> <IGNORE_COUPLING=yes | no> Parameter Description Lxxx Name of a reluctor. Must begin with L, followed by up to 1023 alphanumeric characters n1p n1n ... nNp nNn Names of the connecting terminal nodes. The number of terminals must be even. Each pair of ports represents the location of an inductor. RELUCTANCE Keyword to specify reluctance (inverse inductance). r1, c1, val1, r2, c2, val2, ... rm, cm, valm Reluctance matrix data. In general, K will be sparse and only non-zero values in the matrix need be given. Each matrix entry is represented by a triplet (r,c,val). The value r and c are integers referring to a pair of inductors from the list of terminal nodes. If there are 2*N terminal nodes, there will be N inductors, and the r and c values must be in the range [1,N]. The val value is a reluctance value for the (r,c) matrix location, and the unit for reluctance is the inverse Henry (H-1). Only terms along and above the diagonal are specified for the reluctance_matrix. The simulator fills in the lower triangle to ensure symmetry. If you specify lower diagonal terms, the simulator converts that entry to the appropriate upper diagonal term. If multiple entries are supplied for the same (r,c) location, then only the first one is used, and a warning will be issued indicating that some entries are ignored. All diagonal entries of the reluctance matrix must be assigned a positive value. The reluctance matrix should be positive definite. FILE=”<filename1>” For the external file format, the data files should contain three columns of data. Each row should contain an (r,c,val) triplet separated by white space. The r, c, and val values may be expressions surrounded by single quotes. Multiple files may be specified to allow the reluctance data to be spread over several files if necessary. HSPICE® User Guide: Simulation and Analysis B-2008.09 151 Chapter 8: Elements Passive Elements Parameter Description SHORTALL ■ ■ IGNORE_COUPLING ■ ■ SHORTALL=yes, all inductors in this model are converted to short circuits, and all reluctance matrix values are ignored. SHORTALL=no (default), inductors are not converted to short circuits, and reluctance matrix values are not ignored. IGNORE_COUPLING=yes, all off-diagonal terms are ignored (that is, set to zero). IGNORE_COUPLING=no (default), off-diagonal terms are not ignored. Example This example has 9 segments (or ports) with 12 nodes, and can potentially generate a 9x9 reluctance matrix with 81 elements. L_ThreeNets a 1 1 2 2 a_1 b 4 4 5 5 b_1 c 7 7 8 8 c_1 + RELUCTANCE=( +1 1 103e9 +1 4 -34.7e9 +1 7 -9.95e9 +4 4 114e9 +4 7 -34.7e9 +7 7 103e9 +2 2 103e9 +2 5 -34.7e9 +2 8 -9.95e9 +5 5 114e9 +5 8 -34.7e9 +8 8 103e9 +3 3 103e9 +3 6 -34.7e9 +3 9 -9.95e9 +6 6 114e9 +6 9 -34.7e9 +9 9 103e9 ) + SHORTALL = no IGNORE_COUPLING = no Alternatively, the same element could be specified by using: L_ThreeNets a 1 1 2 2 a_1 b 4 4 5 5 b_1 c 7 7 8 8 c_1 RELUCTANCE + FILE="reluctance.dat" SHORTALL = no IGNORE_COUPLING = no Where reluctance.dat contains: 152 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 8: Elements Multi-Terminal Linear Elements + + + + + + + + + + + + + + + + + + 1 1 1 4 4 7 2 2 2 5 5 8 3 3 3 6 6 9 1 4 7 4 7 7 2 5 8 5 8 8 3 6 9 6 9 9 103e9 -34.7e9 -9.95e9 114e9 -34.7e9 103e9 103e9 -34.7e9 -9.95e9 114e9 -34.7e9 103e9 103e9 -34.7e9 -9.95e9 114e9 -34.7e9 103e9 The following shows the mapping between the port numbers and node pairs: ------------------------------------------------------------------------------------|Ports | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | |Node pairs | (a,1) | (1,2) |(2,a_1)| (b,4) | (4,5) |(5,b_1)| (c,7) | (7,8) |(8,c_1)| ------------------------------------------------------------------------------------- Multi-Terminal Linear Elements A multi-terminal linear element such as a transmission line is a passive element that connects any two conductors at any distance apart. One conductor sends the input signal through the transmission line, and the other conductor receives the output signal from the transmission line. The signal is voltage between the conductors that is transmitted from one end of the pair to the other end. Examples of transmission lines include: ■ Power transmission lines ■ Telephone lines ■ Waveguides ■ Traces on printed circuit boards and multi-chip modules (MCMs) ■ Bonding wires in semiconductor IC packages ■ On-chip interconnections The following sections discuss: HSPICE® User Guide: Simulation and Analysis B-2008.09 153 Chapter 8: Elements Multi-Terminal Linear Elements ■ W-element (Distributed Transmission Lines) ■ U-element (Lumped Transmission Lines) ■ S-element (Generic Multiport) W-element (Distributed Transmission Lines) The W-element supports five different formats to specify the transmission line properties: ■ Model 1: RLGC-Model specification • • ■ Internally specified in a .model statement Externally specified in a different file Model 2: U-Model specification • • Geometric input (planer, coax, twin-lead) • Measured-parameter input • ■ RLGC input for up to five coupled conductors Skin effect Model 3: Built-in field solver model • Standard format (using geometric data with the W-element) • Tabular format ■ Model 4: Frequency-dependent tabular model ■ Model 5: S-parameter Model W-element Statement The general syntax for a lossy (W-element) transmission line element is: RLGC file form: Wxxx in1 <in2 <...inx>> refin out1 <out2 <...outx>> + refout <RLGCfile=filename> N=val L=val U Model form: Wxxx in1 <in2 <...inx>> refin out1 <out2 <...outx>> + refout <Umodel=modelname> N=val L=val Field solver form: 154 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 8: Elements Multi-Terminal Linear Elements Wxxx in1 <in2 <...inx>> refin out1 <out2 <...outx>> + refout <FSmodel=modelname> N=val L=val Table Model form: Wxxx in1 in2 <...inx>> refin out1 <out2 <...outx>> + refout N=val L=val TABLEMODEL=name S Model form: Wxxx in1 <in2 <...inx>> refin out1 <out2 <...outx>> + refout <Smodel=modelname> <NODEMAP=XiYj...> N=val L=val Parameter Description Wxxx Lossy (W-element) transmission line element name. Must start with W, followed by up to 1023 alphanumeric characters. inx Signal input node for xth transmission line (in1 is required). refin Ground reference for input signal outx Signal output node for the xth transmission line (each input port must have a corresponding output port). refout Ground reference for output signal. N Number of conductors (excluding the reference conductor). L Physical length of the transmission line, in units of meters. RLGCfile=filename File name reference for the file containing the RLGC information for the transmission lines (for syntax, see Using the W-element in the HSPICE Signal Integrity Guide). Umodel=modelname U-model lossy transmission-line model reference name. A lossy transmission line model, used to represent the characteristics of the W-element transmission line. FSmodel= modelname Internal field solver model name. References the PETL internal field solver as the source of the transmission-line characteristics (for syntax, see Using the Field Solver Model section in the HSPICE Signal Integrity Guide). HSPICE® User Guide: Simulation and Analysis B-2008.09 155 Chapter 8: Elements Multi-Terminal Linear Elements Parameter Description NODEMAP String that assigns each index of the S parameter matrix to one of the W-element terminals. This string must be an array of pairs that consists of a letter and a number, (for example, Xn), where ■ X= I, i, N, or n to indicate near end (input side) terminal of the W-element ■ X= O, i, F, or f to indicate far end (output side) terminal of the W-element. The default value for NODEMAP is “I1I2I3...InO1O2O3...On” Smodel S Model name reference, which contains the S-parameters of the transmission lines (for the S Model syntax, see the HSPICE Signal Integrity Guide). TABLEMODEL Name of the frequency-dependent tabular model. The number of ports on a single transmission line is not limited. You must provide one input and output port, the ground references, a model or file reference, a number of conductors, and a length. Example 1 The W1 lossy transmission line connects the in node to the out node: W1 in gnd out gnd RLGCfile=cable.rlgc N=1 L=5 Where, ■ Both signal references are grounded ■ The RLGC file is named cable.rlgc ■ The transmission line is 5 meters long. Example 2 The Wcable element is a two-conductor lossy transmission line: Wcable in1 in2 gnd out1 out2 gnd Umodel=umod_1 N=2 + L=10 Where, ■ ■ 156 in1 and in2 input nodes connect to the out1 and out2 output node Both signal references are grounded. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 8: Elements Multi-Terminal Linear Elements ■ umod_1 references the U-model. ■ The transmission line is 10 meters long. Example 3 The Wnet1 element is a five-conductor lossy transmission line: Wnet1 i1 i2 i3 i4 i5 gnd o1 gnd o3 gnd o5 gnd + FSmodel=board1 N=5 L=1m Where, ■ The i1, i2, i3, i4 and i5 input nodes connect to the o1, o3, and o5 output nodes. ■ The i5 input and three outputs (o1, o3, and o5) are all grounded. ■ board1 references the Field Solver model. ■ The transmission line is 1 millimeter long. Example 4: S Model Example Wnet1 i1 i2 gnd o1 o2 gnd + Smodel=smod_1 nodemap=i1i2o1o2 + N=2 L=10m Where, ■ in1 and in2 input nodes connect to the out1 and out2 output node. ■ Both signal references are grounded. ■ smod_1 references the S Model. ■ The transmission line is 10 meters long. You can specify parameters in the W-element card in any order. You can specify the number of signal conductors, N, after the node list. You can also mix nodes and parameters in the W-element card. You can specify only one of the RLGCfile, FSmodel, Umodel, or Smodel models, in a single W-element card. Figure 16 shows node numbering for the element syntax. HSPICE® User Guide: Simulation and Analysis B-2008.09 157 Chapter 8: Elements Multi-Terminal Linear Elements N+1 conductor line [i1]1 1.1 [i ] 12 1.2 [i1]N 1.N 1’ [v1]1 R(f), L(f), G(f), C(f) [v1]2 Signal Conductors [v2]2 . . . . . . [v1]N + _ [i2]2 . . . Reference conductor 2.1 2.2 [i2]N 2.N [v2]N + _ 2’ x 0 Figure 16 [i2]1 [v2]1 Terminal Node Numbering for the W-element For additional information about the W-element, see the W-element Modeling of Coupled Transmission Lines chapter in the HSPICE User Guide: Signal Integrity. U-element (Lumped Transmission Lines) Uxxx in1 <in2 <...in5>> refin out1 <out2 <...out5>> + refout mname L=val <LUMPS=val> Parameter Uxxx Lossy (U-element) transmission line element name. Must begin with U, followed by up to 1023 alphanumeric characters. inx Signal input node for the xth transmission line (in1 is required). refin Ground reference for the input signal. outx Signal output node for the xth transmission line (each input port must have a corresponding output port). refout Ground reference for the output signal. mname 158 Description Model reference name for the U-model lossy transmission-line. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 8: Elements Multi-Terminal Linear Elements Parameter Description L Physical length of the transmission line, in units of meters. LUMPS Number of lumped-parameter sections used to simulate the element. In this syntax, the number of ports on a single transmission line is limited to five in and five out. One input and output port, the ground references, a model reference, and a length are all required. Example 1 The U1 transmission line connects the in node to the out node: U1 in gnd out gnd umodel_RG58 L=5 ■ Both signal references are grounded. ■ umodel_RG58 references the U-model. ■ The transmission line is 5 meters long. Example 2 The Ucable transmission line connects the in1 and in2 input nodes to the out1 and out2 output nodes: Ucable in1 in2 gnd out1 out2 gnd twistpr L=10 ■ Both signal references are grounded. ■ twistpr references the U-model. ■ The transmission line is 10 meters long. Example 3 The Unet1 element is a five-conductor lossy transmission line: Unet1 i1 i2 i3 i4 i5 gnd o1 gnd o3 gnd o5 gnd Umodel1 L=1m ■ The i1, i2, i3, i4, and i5 input nodes connect to the o1, o3, and o5 output nodes. ■ The i5 input, and the three outputs (o1, o3, and o5) are all grounded. ■ Umodel1 references the U-model. ■ The transmission line is 1 millimeter long. HSPICE® User Guide: Simulation and Analysis B-2008.09 159 Chapter 8: Elements Multi-Terminal Linear Elements S-element (Generic Multiport) The S-element uses the following parameters to define a frequency-dependent, multi-terminal network: ■ S (scattering) ■ Y (admittance) You can use an S-element in the following types of analyses: ■ DC ■ AC ■ Transient ■ Small Signal For a description of the S-parameter and SP model analysis, see the S-parameter Modeling Using the S-element chapter in the HSPICE Signal Integrity Guide. Group Delay Handler in Time Domain Analysis The S-element accepts a constant group delay matrix in time-domain analysis. You can also express a weak dependence of the delay matrix on the frequency, as a combination of the constant delay matrix and the phase shift value at each frequency point. To activate or deactivate this delay handler, specify the DELAYHANDLE keyword in the S model statement. The delay matrix is a constant matrix, which HSPICE RF extracts using finite difference calculation at selected target frequency points. HSPICE RF obtains the ϒ ( i, j ) delay matrix component as: ω d θ Sij d θ Sij 1 ϒ ( i, j ) = ------------- = ------ ⋅ ------------ω 2π df dω ■ ■ 160 f is the target frequency, which you can set using DELAYFREQ=val. The default target frequency is the maximum frequency point. θ Sij is the phase of Sij. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 8: Elements Multi-Terminal Linear Elements After time domain analysis obtains the group delay matrix, the following equation eliminates the delay amount from the frequency domain systemtransfer function: y ′ mn ( ω) = y mn ( ω) × e j ωΤ mn The convolution process then uses the following equation to calculate the delay: T i k ( t ) = ( y ′ k1 ( t ), y ′ k2 ( t ), … y ′ kN ( t ) ) × ⎛ v 1 ( t – T ), v 2 ( t – T ), … v Nt – T ⎞ , , ⎝ K1 K2 KN⎠ Preconditioning S-parameters Certain S-parameters, such as series inductor (2-port), show a singularity when converting S to Y parameters. To avoid this singularity, the S-element preconditions S matrices by adding kRref series resistance: S ′ = [ kI + ( 2 – k ) S ] [ ( 2 + k ) I – kS ] –1 ■ Rref is the reference impedance vector. ■ k is the preconditioning factor. To compensate for this modification, the S-element adds a negative resistor (-kRref) to the modified nodal analysis (NMA) matrix, in actual circuit compensation. To specify this preconditioning factor, use the <PREFAC=val> keyword in the S model statement. The default preconditioning factor is 0.75. HSPICE® User Guide: Simulation and Analysis B-2008.09 161 Chapter 8: Elements Active Elements preconditioning S S kRref NMA stamp kRref Y’ Y’ Y Figure 17 Preconditioning S-parameters Active Elements This section describes the active elements: diodes and transistors. Diode Element Geometric (LEVEL=1) or Non-Geometric (LEVEL=3) form: Dxxx nplus nminus mname <<AREA=>area> <<PJ=>val> + <WP=val> <LP=val> <WM=val> <LM=val> <OFF> + <IC=vd> <M=val> <DTEMP=val> Dxxx nplus nminus mname <W=width> <L=length> <WP=val> + <LP=val> <WM=val> <LM=val> <OFF> <IC=vd> <M=val> + <DTEMP=val> Fowler-Nordheim (LEVEL=2) form: 162 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 8: Elements Active Elements Dxxx nplus nminus mname <W=val <L=val>> <WP=val> + <OFF> <IC=vd> <M=val> Parameter Description Dxxx Diode element name. Must begin with D, followed by up to 1023 alphanumeric characters. nplus Positive terminal (anode) node name. The series resistor for the equivalent circuit is attached to this terminal. nminus Negative terminal (cathode) node name. mname Diode model name reference. AREA Area of the diode (unitless for LEVEL=1 diode, and square meters for LEVEL=3 diode). This affects saturation currents, capacitances, and resistances (diode model parameters are IK, IKR, JS, CJO, and RS). The SCALE option does not affect the area factor for the LEVEL=1 diode. Default=1.0. Overrides AREA from the diode model. If you do not specify the AREA, HSPICE or HSPICE RF calculates it from the width and length. PJ Periphery of junction (unitless for LEVEL=1 diode, and meters for LEVEL=3 diode). Overrides PJ from the diode model. If you do not specify PJ, HSPICE or HSPICE RF calculates it from the width and length specifications. WP Width of polysilicon capacitor, in meters (for LEVEL=3 diode only). Overrides WP in the diode model. Default=0.0. LP Length of polysilicon capacitor, in meters (for LEVEL=3 diode only). Overrides LP in the diode model. Default=0.0. WM Width of metal capacitor, in meters (for LEVEL=3 diode only). Overrides WM in the diode model. Default=0.0. LM Length of metal capacitor, in meters (for LEVEL=3 diode only). Overrides LM in the diode model. Default=0.0. OFF Sets the initial condition for this element to OFF, in DC analysis. Default=ON. HSPICE® User Guide: Simulation and Analysis B-2008.09 163 Chapter 8: Elements Active Elements Parameter Description IC=vd Initial voltage, across the diode element. Use this value when you specify the UIC option in the .TRAN statement. The .IC statement overrides this value. M Multiplier, to simulate multiple diodes in parallel. The M setting affects all currents, capacitances, and resistances. Default=1. DTEMP The difference between the element temperature and the circuit temperature, in degrees Celsius. Default=0.0. W Width of the diode, in meters (LEVEL=3 diode model only) L Length of the diode, in meters (LEVEL=3 diode model only) You must specify two nodes and a model name. If you specify other parameters, the nodes and model name must be first and the other parameters can appear in any order. Example 1 The D1 diode, with anode and cathode, connects to nodes 1 and 2. Diode1 specifies the diode model. D1 1 2 diode1 Example 2 The Dprot diode, with anode and cathode, connects to both the output node and ground, references the firstd diode model, and specifies an area of 10 (unitless for LEVEL=1 model). The initial condition has the diode OFF. Dprot output gnd firstd 10 OFF Example 3 The Ddrive diode, with anode and cathode, connects to the driver and output nodes. The width and length are 500 microns. This diode references the model_d diode model. Ddrive driver output model_d W=5e-4 L=5e-4 IC=0.2 Bipolar Junction Transistor (BJT) Element Qxxx nc nb ne <ns> mname <area> <OFF> + <IC=vbeval,vceval> <M=val> <DTEMP=val> 164 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 8: Elements Active Elements Qxxx nc nb ne <ns> mname <AREA=area> <AREAB=val> + <AREAC=val> <OFF> <VBE=vbeval> <VCE=vceval> + <M=val> <DTEMP=val> Parameter Description Qxxx BJT element name. Must begin with Q, then up to 1023 alphanumeric characters. nc Collector terminal node name. nb Base terminal node name. ne Emitter terminal node name. ns Substrate terminal node name, which is optional. You can also use the BULK parameter to set this name in the BJT model. mname BJT model name reference. area, AREA=area Emitter area multiplying factor, which affects currents, resistances, and capacitances. Default=1.0. OFF Sets initial condition for this element to OFF, in DC analysis. Default=ON. IC=vbeval, Initial internal base-emitter voltage (vbeval) and collector-emitter vceval, VBE, voltage (vceval). HSPICE or HSPICE RF uses this value when VCE the .TRAN statement includes UIC. The .IC statement overrides it. M Multiplier, to simulate multiple BJTs in parallel. The M setting affects all currents, capacitances, and resistances. Default=1. DTEMP The difference between the element temperature and the circuit temperature, in degrees Celsius. Default=0.0. AREAB Base area multiplying factor, which affects currents, resistances, and capacitances. Default=AREA. AREAC Collector area multiplying factor, which affects currents, resistances, and capacitances. Default=AREA. The only required fields are the collector, base, and emitter nodes, and the model name. The nodes and model name must precede other fields in the netlist. HSPICE® User Guide: Simulation and Analysis B-2008.09 165 Chapter 8: Elements Active Elements Example 1 In the Q1 BJT element: Q1 1 2 3 model_1 ■ The collector connects to node 1. ■ The base connects to node 2. ■ The emitter connects to node 3. ■ model_1 references the BJT model. Example 2 In the following Qopamp1 BJT element: Qopamp1 c1 b3 e2 s 1stagepnp AREA=1.5 AREAB=2.5 AREAC=3.0 ■ The collector connects to the c1 node. ■ The base connects to the b3 node. ■ The emitter connects to the e2 node. ■ The substrate connects to the s node. ■ 1stagepnp references the BJT model. ■ The AREA area factor is 1.5. ■ The AREAB area factor is 2.5. ■ The AREAC area factor is 3.0. Example 3 In the Qdrive BJT element: Qdrive driver in output model_npn 0.1 ■ ■ The base connects to the in node. ■ The emitter connects to the output node. ■ model_npn references the BJT model. ■ 166 The collector connects to the driver node. The area factor is 0.1. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 8: Elements Active Elements JFETs and MESFETs Jxxx nd ng ns <nb> mname <<<AREA>=area | <W=val> + <L=val>> <OFF> <IC=vdsval,vgsval> <M=val> + <DTEMP=val> Jxxx nd ng ns <nb> mname <<<AREA>=area> | <W=val> + <L=val>> <OFF> <VDS=vdsval> <VGS=vgsval> + <M=val> <DTEMP=val> Parameter Description Jxxx JFET or MESFET element name. Must begin with J, followed by up to 1023 alphanumeric characters. nd Drain terminal node name ng Gate terminal node name ns Source terminal node name nb Bulk terminal node name, which is optional. mname JFET or MESFET model name reference area, AREA=area Area multiplying factor that affects the BETA, RD, RS, IS, CGS, and CGD model parameters. Default=1.0, in units of square meters. W FET gate width in meters L FET gate length in meters OFF Sets initial condition to OFF for this element, in DC analysis. Default=ON. IC=vdsval, vgsval, VDS, VGS Initial internal drain-source voltage (vdsval) and gate-source voltage (vgsval). Use this argument when the .TRAN statement contains UIC. The .IC statement overrides it. M Multiplier to simulate multiple JFETs or MESFETs in parallel. The M setting affects all currents, capacitances, and resistances. Default=1. HSPICE® User Guide: Simulation and Analysis B-2008.09 167 Chapter 8: Elements Active Elements Parameter Description DTEMP The difference between the element temperature and the circuit temperature, in degrees Celsius. Default=0.0. Only drain, gate, and source nodes, and model name fields are required. Node and model names must precede other fields. Example 1 In the J1 JFET element: J1 1 2 3 model_1 ■ The drain connects to node 1. ■ The source connects to node 2. ■ The gate connects to node 3. ■ model_1 references the JFET model. Example 2 In the following Jopamp1 JFET element: Jopamp1 d1 g3 s2 b 1stage AREA=100u ■ The drain connects to the d1 node. ■ The source connects to the g3 node. ■ The gate connects to the s2 node. ■ 1stage references the JFET model. ■ The area is 100 microns. Example 3 In the Jdrive JFET element: Jdrive driver in output model_jfet W=10u L=10u ■ ■ The source connects to the in node. ■ The gate connects to the output node. ■ model_jfet references the JFET model. ■ The width is 10 microns. ■ 168 The drain connects to the driver node. The length is 10 microns. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 8: Elements Active Elements MOSFETs Mxxx nd ng ns <nb> mname <<L=>length> <<W=>width> + <AD=val> AS=val> <PD=val> <PS=val> + <NRD=val> <NRS=val> <RDC=val> <RSC=val> <OFF> + <IC=vds,vgs,vbs> <M=val> <DTEMP=val> + <GEO=val> <DELVTO=val> .OPTION WL Mxxx nd ng ns <nb> mname <width> <length> <other_options...> Parameter Description Mxxx MOSFET element name. Must begin with M, followed by up to 1023 alphanumeric characters. nd Drain terminal node name. ng Gate terminal node name. ns Source terminal node name. nb Bulk terminal node name, which is optional. To set this argument in the MOSFET model, use the BULK parameter. mname MOSFET model name reference or subckt name if .OPTION MACMOD is set. L MOSFET channel length, in meters. This parameter overrides .OPTION DEFL, with a maximum value of 0.1m. Default=DEFL. W MOSFET channel width, in meters. This parameter overrides .OPTION DEFW. Default=DEFW. AD Drain diffusion area. Overrides .OPTION DEFAD. Default=DEFAD, if you set the ACM=0 model parameter. AS Source diffusion area. Overrides .OPTION DEFAS. Default=DEFAS, if you set the ACM=0 model parameter. PD Perimeter of drain junction, including channel edge. Overrides.OPTION DEFPD. Default=DEFAD, if you set the ACM=0 or 1 model parameter. Default=0.0, if you set ACM=2 or 3. HSPICE® User Guide: Simulation and Analysis B-2008.09 169 Chapter 8: Elements Active Elements Parameter Description PS Perimeter of source junction, including channel edge. Overrides .OPTION DEFPS. Default=DEFAS, if you set the ACM=0 or 1 model parameter. Default=0.0, if you set ACM=2 or 3. NRD Number of squares of drain diffusion for resistance calculations. Overrides .OPTION DEFNRD. Default=DEFNRD, if you set ACM=0 or 1 model parameter. Default=0.0, if you set ACM=2 or 3. NRS Number of squares of source diffusion for resistance calculations. Overrides .OPTION DEFNRS. Default=DEFNRS when you set the MOSFET model parameter ACM=0 or 1. Default=0.0, when you set ACM=2 or 3. RDC Additional drain resistance due to contact resistance, in units of ohms. This value overrides the RDC setting in the MOSFET model specification. Default=0.0. RSC Additional source resistance due to contact resistance, in units of ohms. This value overrides the RSC setting in the MOSFET model specification. Default=0.0. OFF Sets initial condition for this element to OFF, in DC analysis. Default=ON. This command does not work for depletion devices. IC=vds, vgs, vbs Initial voltage across external drain and source (vds), gate and source (vgs), and bulk and source terminals (vbs). Use these arguments with .TRAN UIC. .IC statements override these values. M Multiplier, to simulate multiple MOSFETs in parallel. Affects all channel widths, diode leakages, capacitances, and resistances. Default=1. DTEMP The difference between the element temperature and the circuit temperature, in degrees Celsius. Default=0.0. GEO Source/drain sharing selector for a MOSFET model parameter value of ACM=3. Default=0.0. DELVTO Zero-bias threshold voltage shift. Default=0.0. The only required fields are the drain, gate and source nodes, and the model name. The nodes and model name must precede other fields in the netlist. If you did not specify a label, use the second syntax with the .OPTION WL statement, to exchange the width and length options. 170 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 8: Elements Active Elements Example In the following M1 MOSFET element: M1 1 2 3 model_1 ■ The drain connects to node 1. ■ The gate connects to node 2. ■ The source connects to node 3. ■ model_1 references the MOSFET model. In the following Mopamp1 MOSFET element: Mopamp1 d1 g3 s2 b 1stage L=2u W=10u ■ The drain connects to the d1 node. ■ The gate connects to the g3 node. ■ The source connects to the s2 node. ■ 1stage references the MOSFET model. ■ The length of the gate is 2 microns. ■ The width of the gate is 10 microns. In the following Mdrive MOSFET element: Mdrive driver in output bsim3v3 W=3u L=0.25u DTEMP=4.0 ■ The drain connects to the driver node. ■ The gate connects to the in node. ■ The source connects to the output node. ■ bsim3v3 references the MOSFET model. ■ The length of the gate is 3 microns. ■ The width of the gate is 0.25 microns. ■ The device temperature is 4 ° Celsius higher than the circuit temperature. Extended MOSFET Element Support Using .OPTION MACMOD Use option MACMOD to enable HSPICE MOSFET to access a subckt definition when no model reference exists. .OPTION MACMOD syntax is: .OPTION MACMOD= [1|2|3|0] HSPICE® User Guide: Simulation and Analysis B-2008.09 171 Chapter 8: Elements Active Elements When macmod=1, HSPICE seeks a subckt definition for the M*** element if no model reference exists. The desired subckt name must match (case insensitive) the mname field in the M*** instance statement. In addition, the number of terminals of the subckt must match with the M*** element referencing it; otherwise HSPICE aborts the simulation based on no definition for the M*** element. The following limitations apply when macmod=1: 1. Element template output does not support MOSFET elements which use subckt definitions. 2. This feature will not support a MOSFET element whose mname is defined by a string parameter. 3. The number of terminals for a HSPICE MOSFET element must be within the range of 3-7; any number of terminals that is out of this range will cause the simulation to fail. When macmod=2, HSPICE seeks a MOSFET model definition when it cannot find matching subckt or Verilog-A definition for an X-element. The targeted MOSFET MODEL card could be either HSPICE built-in MOSFET model or CMI MOSFET model. If the model card that matched with the X-element reference name is not a type of MOSFET models, simulator errors out with message of reference not found. The following limitations apply when macmod=2: 1. The feature of “string parameter supported in MOSFET model name” is not applied to X-elements that are mapped to MOSFET model cards; i.e., reference name of the X-element must be constant string characters. 2. Subckt direct port probing command, isub() is not supported on Xelements mapped to MOSFET model cards. 3. HSPICE MOSRA analysis may not be performed on the X-elements, even when they direct map to MOSFET model cards. When macmod=3, HSPICE enables both of the above features; HSPICE seeks a .subckt definition for an M-element if there is no matching model reference; HSPICE seeks a .model MOSFET definition for an X-element if there is no matching .subckt or Verilog-A definition. Usage considerations and limitations remain the same for both features, respectively. 172 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 8: Elements Active Elements Note: When MACMOD=2 or 3, for the X-element that maps to an M-element, if it has an instance parameter named ‘Multi’ (case insensitive), then ‘Multi’ is aliased to the ‘M’ factor, the M (multiply) parameter. When macmod=0, if there is no .option MACMOD in the input files or MACMOD=0, then neither of the above two features is enabled; HSPICE ignores the MACMOD option when any value other than 1|2|3|0 is set. The MACMOD option is a global option; if there are multiple MACMOD options in one simulation, HSPICE uses the value of the last MACMOD option. Example 1 ** .option MACMOD=1 M1 net1 net2 net3 net4 nch l=0.2u w=0.2u p1=1 .model nch nmos level=49 …. .subckt nch d g s b w=1 l=1 p1=gp1 .if (p1 > 0) Mnch d g s b model_1 w=w l=l .else Mnch d g s b model_2 w=w l=l .endif .ends In Example 1, extended MOSFET is turned on. However, because the mname in a.MODEL statement matches the mname of the M1 element, element M1uses model nch rather than the subckt definition. The extra instance parameter p1 is ignored. Example 2 ** .option MACMOD .param gp1=1 gp2=2 gp3=3 M1 net1 net2 net3 net4 nch l=0.2u w=0.2u p1=gp1 p2=gp2 p3=gp3 .subckt nch d g s b w=1 l=1 p1=gp1 p2=gp2 p3=gp3 .if (p1 > 0 && p2==1 && p3 ==1) Mnch d g s b model_1 w=w l=l .else if ( p1 == 0 && p2 ==1 && p3 ==1) Mnch d g s b model_2 w=w l=l .else Mnch d g s b model_3 w=w l=l .endif .ends .model model_1 nmos level=49 ... .model model_2 nmos level=53 ... .model model_3 nmos level=54 ... HSPICE® User Guide: Simulation and Analysis B-2008.09 173 Chapter 8: Elements Active Elements In Example 2, extended MOSFET element support is turned on; since there is no matching .MODEL statement, M1 uses subckt definition nch; after evaluation, M1 results in a MOSFET element using MOSFET model model_3. Example 3 ** .option MACMOD .param gp1=1 gp2=2 gp3=3 M1 net1 net2 net3 net4 nch l=0.2u w=0.2u p1=gp1 p2=gp2 p3=gp3 .subckt nch d g s b w=1 l=1 p1=gp1 p2=gp2 p3=gp3 .if (p1 > 0 && p2==1 && p3 ==1) Mnch d g s b model_1 w=w l=l .else if ( p1 == 0 && p2 ==1 && p3 ==1) Mnch d g s b model_2 w=w l=l .else Mnch d g s b model_3 w=w l=l .endif C1 g 0 1p .ends Example 3 shows extended MOSFET element support turned on. Instance M1 uses macro model nch, which is a subckt definition that consists of one MOSFET device and one capacitor. MACMOD Option Limitations ■ The number of terminals for M*** must be within the range of 3 to 7. A number of terminals outside of that range cause the simulation to fail. ■ This feature does not support a MOSFET element whose mname is defined by a string parameter. ■ The MACMOD option only applies to HSPICE MOSFET elements. ■ Element template output does not support MOSFET elements which use subckt definitions. For example, if Example 3 includes the output command: .PRINT LX8(M1) LV9(M1) —then HSPICE ignores the above output command. Because M1 is using a subckt definition, it is no longer a HSPICE primitive MOSFET device. 174 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 8: Elements Active Elements ■ The desired subckt name must match the mname field in the M*** instance statement. The match of subckt name and the mname field is case insensitive. ■ The .MODEL definition will always be used over a subckt definition even when .OPTION MACMOD is on. Direct X-Element Mapping to a MOSFET Model Card HSPICE will look for a MOSFET model definition when it cannot find a matching subckt or Verilog-A definition for an X-element. This applies mainly to a CMI model, which is turned on only when the .option CMIFLAG is set; Subckt or Verilog-A module definitions will always take preference over the CMI model card. The X-elements that are mapped to model cards are treated as HSPICE MOSFET devices with certain usage considerations and limitations described in the following sections. For information about the HSPICE CMI, contact your Synopsys support team. Considerations Syntax check rules of MOSFET devices will be applied to the X-elements directly mapping to MOSFET model cards, such as: 1. The valid instance parameter list of that X-element will then be the valid instance parameter list of the particular MOSFET model defined in the mapping model card, any invalid instance parameter of that X-element will be ignored; any undefined instance parameter comparing with the corresponding MOSFET model, is set to default values of the mapping MOSFET model; implicit instance parameters of the mapping MOSFET model are applied to such X-elements instead of the implicit parameter set of a conventional X-element. 2. MOSFET instance parameters are device native parameters, not the netlist parameter, so they cannot be overridden by the .PARAM netlist commands; such instance parameter rules are applied to X-elements with direct mapping to MOSFET model cards, i.e., instance parameters of such an Xelement become native device parameters, thus cannot be overridden by netlist .PARAM commands. 3. The number of terminals of the X-element must be in the valid range of its mapping MOSFET model; or simulator exits with an error message. HSPICE® User Guide: Simulation and Analysis B-2008.09 175 Chapter 8: Elements IBIS Buffers (HSPICE Only) Limitations 1. The feature of “string parameter supported on MOSFET model name” is not applied to X-elements that are mapped to MOSFET model cards. In other words, a reference name of the X-element must be written as constant string characters. 2. The Subckt direct port probing command, Isub() is not supported on Xelements mapped to MOSFET model cards. 3. HSPICE MOSRA analysis may not be performed on the X-elements, even if they directly map to MOSFET model cards. IBIS Buffers (HSPICE Only) The general syntax of a B-element card for IBIS I/O buffers is: bxxx node_1 node_2 ... node_N + file='filename' model='model_name' + keyword_1=value_1 ... [keyword_M=value_M] Parameter Description bname Buffer name, and starts with the letter B, which can be followed by up to 1023 alphanumeric characters. node_1 node_2 ... node_N List of I/O buffer external nodes. The number of nodes and their meaning are specific to different buffer types. file=’filename’ Name of the IBIS file. model=’model_name’ Name of the model. keyword_i=value_i Assigns a value of value_i to the keyword_i keyword. Specify optional keywords in brackets ( [ ] ). For more information about IBIS keywords, see Specifying Common Keywords in the HSPICE User Guide: Signal Integrity. Example B1 nd_pc nd_gc nd_in nd_out_of_in + buffer=1 + file='test.ibs' + model='IBIS_IN' 176 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 8: Elements IBIS Buffers (HSPICE Only) ■ This example represents an input buffer named B1. ■ The four terminals are named nd_pc, nd_gc, nd_in and nd_out_of_in. ■ The IBIS model named IBIS_IN is located in the IBIS file named test.ibs. Note: HSPICE connects the nd_pc and nd_gc nodes to the voltage sources. Do not manually connect these nodes to voltage sources. For more examples, see the Modeling Input/Output Buffers Using IBIS Files chapter in the HSPICE User Guide: Signal Integrity. HSPICE® User Guide: Simulation and Analysis B-2008.09 177 Chapter 8: Elements IBIS Buffers (HSPICE Only) 178 HSPICE® User Guide: Simulation and Analysis B-2008.09 9 9 Sources and Stimuli Describes element and model statements for independent sources, dependent sources, analog-to-digital elements, and digital-to-analog elements supported by HSPICE and HSPICE RF. This chapter also explains each type of element and model statement and provides explicit formulas and examples to show how various combinations of parameters affect the simulation. These topics are discussed in the following sections: ■ Independent Source Elements ■ Independent Source Functions ■ Voltage and Current Controlled Elements ■ Voltage-Dependent Voltage Sources — E-elements ■ Current-Dependent Current Sources — F-elements ■ Voltage-Dependent Current Sources — G-elements ■ Current-Dependent Voltage Sources — H-elements ■ Specifying a Digital Vector File and Mixed Mode Stimuli Independent Source Elements Use independent source element statements to specify DC, AC, transient, and mixed independent voltage and current sources. Depending on the analysis performed, the associated analysis sources are used. The value of the DC source is overridden by the zero time value of the transient source when a transient operating point is calculated. HSPICE® User Guide: Simulation and Analysis B-2008.09 179 Chapter 9: Sources and Stimuli Independent Source Elements Source Element Conventions You do not need to ground voltage sources. HSPICE assumes that positive current flows from the positive node, through the source, to the negative node. A positive current source forces current to flow out of the n+ node, through the source, and into the n- node. You can use parameters as values in independent sources. Do not use any of the following reserved keywords to identify these parameters: AC, ACI, AM, DC, EXP, PAT, PE, PL, PU, PULSE, PWL, R, RD, SFFM, or SIN Independent Source Element Syntax Vxxx n+ n- [[DC=] dcval tranfun [AC=acmag acphase]] Ixxx n+ n- [[DC=] dcval tranfun [AC=acmag acphase]] + [M=val] Parameter Vxxx Independent voltage source element name. Must begin with V, followed by up to 1023 alphanumeric characters. Ixxx Independent current source element name. Must begin with I, followed by up to 1023 alphanumeric characters. n+ Positive node. n- Negative node. DC=dcval DC source keyword and value, in volts. The tranfun value at time zero overrides the DC value. Default=0.0. tranfun Transient source function (one or more of: AM, DC, EXP, PAT, PE, PL, PU, PULSE, PWL, SFFM, SIN). The functions specify the characteristics of a time-varying source. See the individual functions for syntax. AC AC source keyword for use in AC small-signal analysis. acmag Magnitude (RMS) of the AC source, in volts. acphase 180 Description Phase of the AC source, in degrees. Default=0.0. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Independent Source Elements Parameter Description M Multiplier, to simulate multiple parallel current sources. HSPICE or HSPICE RF multiplies source current by M. Default=1.0. Example 1 VX 1 0 5V Where, ■ The VX voltage source has a 5-volt DC bias. ■ The positive terminal connects to node 1. ■ The negative terminal is grounded. Example 2 VB 2 0 DC=VCC Where, ■ The VCC parameter specifies the DC bias for the VB voltage source. ■ The positive terminal connects to node 2. ■ The negative terminal is grounded. Example 3 VH 3 6 DC=2 AC=1,90 Where, ■ The VH voltage source has a 2-volt DC bias, and a 1-volt RMS AC bias, with 90 degree phase offset. ■ The positive terminal connects to node 3. ■ The negative terminal connects to node 6. Example 4 IG 8 7 PL(1MA 0S 5MA 25MS) Where, ■ The piecewise-linear relationship defines the time-varying response for the IG current source, which is 1 milliamp at time=0, and 5 milliamps at 25 milliseconds. ■ The positive terminal connects to node 8. ■ The negative terminal connects to node 7. HSPICE® User Guide: Simulation and Analysis B-2008.09 181 Chapter 9: Sources and Stimuli Independent Source Elements Example 5 VCC in out VCC PWL 0 0 10NS VCC 15NS VCC 20NS 0 Where, ■ The VCC parameter specifies the DC bias for the VCC voltage source. ■ The piecewise-linear relationship defines the time-varying response for the VCC voltage source, which is 0 volts at time=0, VCC from 10 to 15 nanoseconds, and back to 0 volts at 20 nanoseconds. ■ The positive terminal connects to the in node. ■ The negative terminal connects to the out node. ■ HSPICE or HSPICE RF determines the operating point for this source, without the DC value (the result is 0 volts). Example 6 VIN 13 2 0.001 AC 1 SIN (0 1 1MEG) Where, ■ The VIN voltage source has a 0.001-volt DC bias, and a 1-volt RMS AC bias. ■ The sinusoidal time-varying response ranges from 0 to 1 volts, with a frequency of 1 megahertz. ■ The positive terminal connects to node 13. ■ The negative terminal connects to node 2. Example 7 ISRC 23 21 AC 0.333 45.0 SFFM (0 1 10K 5 1K) Where, ■ The ISRC current source has a 1/3-amp RMS AC response, with a 45degree phase offset. ■ The frequency-modulated, time-varying response ranges from 0 to 1 volts, with a carrier frequency of 10 kHz, a signal frequency of 1 kHz, and a modulation index of 5. ■ The positive terminal connects to node 23. ■ The negative terminal connects to node 21. Example 8 VMEAS 12 9 Where, 182 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Independent Source Elements ■ The VMEAS voltage source has a 0-volt DC bias. ■ The positive terminal connects to node 12. ■ The negative terminal connects to node 9. DC Sources For a DC source, you can specify the DC current or voltage in different ways: V1 V1 I1 I1 1 1 1 1 0 0 0 0 DC=5V 5V DC=5mA 5mA ■ The first two examples specify a DC voltage source of 5 V, connected between node 1 and ground. ■ The third and fourth examples specify a 5 mA DC current source, between node 1 and ground. The direction of current in both sources is from node 1 to ground. AC Sources AC current and voltage sources are impulse functions, used for an AC analysis. To specify the magnitude and phase of the impulse, use the AC keyword. V1 1 0 AC=10V,90 VIN 1 0 AC 10V 90 The preceding two examples specify an AC voltage source, with a magnitude of 10 V and a phase of 90 degrees. To specify the frequency sweep range of the AC analysis, use the .AC analysis statement. Transient Sources For transient analysis, you can specify the source as a function of time. The following functions are available: ■ Trapezoidal pulse (PULSE function) ■ Sinusoidal (SIN function) ■ Exponential (EXP function) HSPICE® User Guide: Simulation and Analysis B-2008.09 183 Chapter 9: Sources and Stimuli Independent Source Elements ■ Piecewise linear (PWL function) ■ Single-frequency FM (SFFM function) ■ Single-frequency AM (AM function) ■ Pattern (PAT function) ■ Pseudo Random-Bit Generator Source (PRBS function) Mixed Sources Mixed sources specify source values for more than one type of analysis. For example, you can specify a DC source, an AC source, and a transient source, all of which connect to the same nodes. In this case, when you run specific analyses, HSPICE or HSPICE RF selects the appropriate DC, AC, or transient source. If the mixed source DC value is missing, the zero-time value of its transient source will be used as the DC value by default. Otherwise, for DC analysis, the DC source value is used by the program, and is selected for operating point calculation for all analysis except TRAN; for TRAN analysis, an additional operating point is calculation with the zero-time source transient value. Example VIN 13 2 0.5 AC 1 SIN (0 1 1MEG) Where, ■ DC source of 0.5 V ■ AC source of 1 V ■ Transient damped sinusoidal source Each source connects between nodes 13 and 2. For DC analysis, the program uses its dc value 0.5v, and this operating point is selected for the coming AC analysis. For transient analysis, another operating point is calculated by using zero source value because the sinusoidal source is zero at time zero. Port Element The port element (P-element) identifies the ports used in .LIN analysis. Each port element requires a unique port number. If your design uses N port 184 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Independent Source Elements elements, your netlist must contain the sequential set of port numbers, 1 through N (for example, in a design containing 512 ports, you must number each port sequentially, 1 to 512). Each port has an associated system impedance, zo. If you do not explicitly specify the system impedance, the default is 50 ohms. The port element behaves as either a noiseless impedance or a voltage source in series with the port impedance for all other analyses (DC, AC, or TRAN). ■ You can use this element as a pure terminating resistance or as a voltage or power source. ■ You can use the RDC, RAC, RHB, RHBAC, and RTRAN values to override the port impedance value for a particular analysis. The port element accepts transient waveforms AM, EXP, PULSE, PWL, SFFM, SIN, and, for signal integrity usage, the PAT source. Pxxx p n port=portnumber + \$ **** Voltage or Power Information ******** + [DC mag] [AC mag phase] [HBAC mag phase] + [HB mag phase harm tone modharm modtone] + [transient_waveform] [TRANFORHB=[0|1]] + [DCOPEN=[0|1]] + \$ **** Source Impedance Information ******** + [Z0=val] [RDC=val] [RAC=val] + [RHBAC=val] [RHB=val] [RTRAN=val] + \$ **** Power Switch ******** + [power=[0|1|2|W|dbm]] Parameter Description port=portnumber The port number. Numbered sequentially beginning with 1 with no shared port numbers. DC mag DC voltage or power source value. AC mag phase AC voltage or power source value. HBAC mag phase (HSPICE RF) HBAC voltage or power source value. HSPICE® User Guide: Simulation and Analysis B-2008.09 185 Chapter 9: Sources and Stimuli Independent Source Elements Parameter Description HB mag phase harm tone modharm modtone (HSPICE RF) HB voltage, current, or power source value. Multiple HB specifications with different harm, tone, modharm, and modtone values are allowed. ■ ■ ■ phase is in degrees harm and tone are indices corresponding to the tones specified in the .HB statement. Indexing starts at 1 (corresponding to the first harmonic of a tone). modtone and modharm specify sources for multi-tone simulation. A source specifies a tone and a harmonic, and up to 1 offset tone and harmonic (modtone for tones and modharm for harmonics). The signal is then described as: V(or I)=mag*cos(2*pi* (harm*tone+modharm*modtone)*t + phase) transient_waveform (Transient analysis) Voltage or power source waveform. Any one of waveforms: AM, EXP, PULSE, PWL, SFFM, SIN, or PRBS. Multiple transient descriptions are not allowed. TRANFORHB=[0|1] ■ 186 (HSPICE RF) 0 (default): The transient description is ignored if an HB value is given or a DC value is given. If no DC or HB value is given and TRANFORHB=0, then HB analysis treats the source as a DC source, and the DC source value is the time=0 value. ■ 1: HB analysis uses the transient description if its value is VMRF, SIN, PULSE, PWL, or LFSR. If the type is a nonrepeating PWL source, then the time=infinity value is used as a DC analysis source value. For example, the following statement is treated as a DC source with value=1 for HB analysis: v1 1 0 PWL (0 0 1n 1 1u 1) + TRANFORHB=1 In contrast, the following statement is a 0V DC source: v1 1 0 PWL (0 0 1n 1 1u 1) + TRANFORHB=0 The following statement is treated as a periodic source with a 1us period that uses PWL values: v1 1 0 PWL (0 0 1n 1 0.999u 1 1u 0) R + TRANFORHB=1 To override the global TRANFORHB option, explicitly set TRANFORHB for a voltage or current source. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Independent Source Elements Parameter Description DCOPEN Switch for open DC connection when DC mag is not set. ■ ■ z0=val> 0 (default): P element behaves as an impedance termination. 1 : P element is considered an open circuit in DC operating point analysis. DCOPEN=1 is mainly used in .LIN analysis so the P element will not affect the self-biasing device under test by opening the termination at the operating point. (LIN analysis) System impedance used when converting to a power source, inserted in series with the voltage source. Currently, this only supports real impedance. ■ When power=0, z0 defaults to 0. When power=1, z0 defaults to 50 ohms. You can also enter zo=val. ■ RDC=val (DC analysis) Series resistance (overrides z0). RAC=val (AC analysis) Series resistance (overrides z0). RHBAC=val (HSPICE RF HBAC analysis) Series resistance (overrides z0). RHB=val (HSPICE RF HB analysis) Series resistance (overrides z0). RTRAN=val (Transient analysis) Series resistance (overrides z0). power=[0 | 1 | 2 | W | dbm] (HSPICE RF) power switch ■ When 0 (default), element treated as a voltage or current source. ■ When 1 or W, element treated as a power source, realized as a voltage source with a series impedance. In this case, the source value is interpreted as RMS available power in units of Watts. ■ When 2 or dbm, element treated as a power source in series with the port impedance. Values are in dbms. You can use this parameter for transient analysis if the power source is either DC or SIN. Example For example, the following port element specifications identify a 2-port network with 50-Ohm reference impedances between the “in” and “out” nodes. P1 in gnd port=1 z0=50 P2 out gnd port=2 z0=50 HSPICE® User Guide: Simulation and Analysis B-2008.09 187 Chapter 9: Sources and Stimuli Independent Source Functions Computing scattering parameters requires z0 reference impedance values. The order of the port parameters (in the P Element) determines the order of the S, Y, and Z parameters. Unlike the .NET command, the .LIN command does not require you to insert additional sources into the circuit. To calculate the requested transfer parameters, HSPICE automatically inserts these sources as needed at the port terminals. You can define an unlimited number of ports. Independent Source Functions HSPICE or HSPICE RF uses the following types of independent source functions: ■ Trapezoidal pulse (PULSE function) ■ Sinusoidal (SIN function) ■ Exponential (EXP function) ■ Piecewise linear (PWL function) ■ Single-frequency FM (SFFM function) ■ Single-frequency AM (AM function) ■ Pattern (PAT function) ■ Pseudo Random-Bit Generator Source (PRBS function) HSPICE also provides a data-driven version of PWL (not supported in HSPICE RF). If you use the data-driven PWL, you can reuse the results of an experiment or of a previous simulation, as one or more input sources for a transient simulation. If you use the independent sources supplied with HSPICE or HSPICE RF, you can specify several useful analog and digital test vectors for steady state, time domain, or frequency domain analysis. For example, in the time domain, you can specify both current and voltage transient waveforms, as exponential, sinusoidal, piecewise linear, AM, or single-sided FM functions, and pattern (for HSPICE signal integrity). Trapezoidal Pulse Source HSPICE or HSPICE RF provides a trapezoidal pulse source function, which starts with an initial delay from the beginning of the transient simulation interval, to an onset ramp. During the onset ramp, the voltage or current changes 188 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Independent Source Functions linearly from its initial value to the pulse plateau value. After the pulse plateau, the voltage or current moves linearly along a recovery ramp back to its initial value. The entire pulse repeats, with a period named per, from onset to onset. Vxxx n+ n- PU[LSE] [(]v1 v2 [td [tr [tf [pw [per]]]]] [)] + [PERJITTER=val [SEED=val]] Ixxx n+ n- PU[LSE] [(]v1 v2 [td [tr [tf [pw [per]]]]] [)] + [PERJITTER=val [SEED=val]] Parameter Description Vxxx, Ixxx Independent voltage source, which exhibits the pulse response. PULSE Keyword for a pulsed time-varying source. The short form is PU. v1 Initial value of voltage or current before the pulse onset (units: volts/amps). v2 Pulse plateau value (units of volts or amps). td Delay (propagation) time in seconds from the beginning of the transient interval to the first onset ramp. Default=0.0 tr Duration of the onset ramp (in seconds) from the initial value to the pulse plateau value (reverse transit time). Default=TSTEP. tf Duration of the recovery ramp (in seconds) from the pulse plateau back to the initial value (forward transit time). Default=TSTEP. pw Pulse width (the width of the plateau portion of the pulse), in seconds. Default=TSTOP. per Pulse repetition period, in seconds. Default=TSTOP. perjitter RMS value for period jitter, adjusts the magnitude of the random time. seed Used to generate random number sequences with different seed value. The value is a negative integer, defaults to -1. Table 11 Time-Value Relationship for a PULSE Source Time Value 0 v1 HSPICE® User Guide: Simulation and Analysis B-2008.09 189 Chapter 9: Sources and Stimuli Independent Source Functions Table 11 Time-Value Relationship for a PULSE Source (Continued) Time Value td v1 td + tr v2 td + tr + pw v2 td + tr + pw + tf v1 tstop v1 Linear interpolation determines the intermediate points. Note: TSTEP is the printing increment, and TSTOP is the final time. Effect of Jitter on the PULSE Source The effect of jitter on the PULSE source results in random shifts of the rise and fall transitions that normally take place at: RISE edge: td + n ⋅ T 0 ≤ t ≤ td + n ⋅ T 0 FALL edge: td + pw + n ⋅ T 0 ≤ t ≤ td+ tr + pw + tf + n ⋅ T 0 The jitter effect is equivalent to introducing random shifts in the period 0 T consistent with the 1st order jitter model based on Period Jitter, also according to the expression for period variations T 0 →T j = T 0 + Δ T ( t ) . The first period of the PULSE source is also guaranteed to be that specified in the syntax, yet all subsequent pulse periods are random according to T 0 + Δ T ( t ) . The PULSE source with jitter will still maintain constant rise and fall times. This creates some uncertainty in how the pulse width ( pw ) varies as the period varies due to jitter. HSPICE RF uses a special calculation that holds the rise and fall times ( tr and tf ) constant, and also holds the 50% Duty Cycle constant. Note that the 50% duty cycle is defined based on the halfway points on the rise and fall times. The result is that the pulse width ( pw ) change due to jitter variations is given by: 190 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Independent Source Functions Tj Tj 1 pw j = pw ⋅ ⎛ -----⎞ + -- ⋅ ( t r + tf ) ⋅ ⎛ ----- – 1⎞ ⎝ T 0⎠ 2 ⎝ T0 ⎠ Also, this sets the minimum period for a PULSE source with jitter to be tr + tf , resulting in the extreme case of a sawtooth waveform. A Gaussian random number generator is used to compute the random Δ T ( t ) variations after each leading edge of the clock sources. For flexibility, the SEED parameter (integer) is supported for generating different random number sequences when different SEED integers are used for initialization. Example 1 The following example shows the pulse source, connected between node 3 and node 0. In the pulse: ■ The output high voltage is 1 V. ■ The output low voltage is -1 V. ■ The delay is 2 ns. ■ The rise and fall time are each 2 ns. ■ The high pulse width is 50 ns. ■ The period is 100 ns. ■ The RMS value for period jitter is 10ns. ■ The seed is -1. VIN 3 0 PULSE (-1 1 2NS 2NS 2NS 50NS 100NS) perjitter=10ns seed=-1 Example 2 The following example is a pulse source, which connects between node 99 and node 0. The syntax shows parameter values for all specifications. V1 99 0 PU lv hv tdlay tris tfall tpw tper Example 3 The following example shows an entire netlist, which contains a PULSE voltage source. In the source: ■ The initial voltage is 1 volt. ■ The pulse voltage is 2 volts. ■ The delay time, rise time, and fall time are each 5 nanoseconds. HSPICE® User Guide: Simulation and Analysis B-2008.09 191 Chapter 9: Sources and Stimuli Independent Source Functions ■ The pulse width is 20 nanoseconds. ■ The pulse period is 50 nanoseconds. This example is based on demonstration netlist pulse.sp, which is available in directory \$installdir/demo/hspice/sources: file pulse.sp test of pulse .option post .tran .5ns 75ns vpulse 1 0 pulse( v1 v2 td tr tf pw per ) r1 1 0 1 .param v1=1v v2=2v td=5ns tr=5ns tf=5ns pw=20ns per=50ns .end Figure 18 shows the result of simulating this netlist, in HSPICE or HSPICE RF. Figure 18 Pulse Source Function Sinusoidal Source Function HSPICE or HSPICE RF provides a damped sinusoidal source function, which is the product of a dying exponential with a sine wave. To apply this waveform, you must specify: 192 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Independent Source Functions ■ Sine wave frequency ■ Exponential decay constant ■ Beginning phase ■ Beginning time of the waveform Vxxx n+ n- SIN [(] vo va [freq [td [q [j]]]] [)] + [[PERJITTER=val] [SEED=val]] Ixxx n+ n- SIN [(] vo va [freq [td [q [j]]]] [)] + [[PERJITTER=val] [SEED=val]] Parameter Description Vxxx, Ixxx Independent voltage source that exhibits the sinusoidal response. SIN Keyword for a sinusoidal time-varying source. vo Voltage or current offset, in volts or amps. va Voltage or current peak value (vpeak), in volts or amps. freq Source frequency in Hz. Default=1/TSTOP. td Time (propagation) delay before beginning the sinusoidal variation, in seconds. Default=0.0. Response is 0 volts or amps, until HSPICE or HSPICE RF reaches the delay value, even with a non-zero DC voltage. q Damping factor, in units of 1/seconds. Default=0.0. j Phase delay, in units of degrees. Default=0.0. perjitter RMS value for period jitter, used to adjust the magnitude of the random time. seed Used to generate random number sequences with different seed value. The value is a negative integer, defaults to -1. HSPICE® User Guide: Simulation and Analysis B-2008.09 193 Chapter 9: Sources and Stimuli Independent Source Functions The following table of expressions defines the waveform shape: Table 12 Waveform Shape Expressions Time Value 0 to td 2⋅ Π⋅ ϕ vo + va ⋅ SIN ⎛ ------------------------ ⎞ ⎝ 360 ⎠ td to tstop vo + va ⋅ Exp [ – ( T ime – td ) ⋅ q ] ⋅ ⎧ SIN ⎨ 2 ⋅ Π ⋅ ⎩ j freq ⋅ ( time – td + x ( t ) ) + -------- ⎫ 360 ⎬ ⎭ Where q and j are the damping factor and phase delay in the syntax. In these expressions, TSTOP is the final time. Example VIN 3 0 SIN (0 1 100MEG 1NS 1e10) This damped sinusoidal source connects between nodes 3 and 0. In this waveform: ■ Peak value is 1 V. ■ Offset is 0 V. ■ Frequency is 100 MHz. ■ Time delay is 1 ns. ■ Damping factor is 1e10. ■ Phase delay is zero degrees. See Figure 19 on page 195 for a plot of the source output. 194 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Independent Source Functions Figure 19 Sinusoidal Source Function This example is based on demonstration netlist sin.sp, which is available in directory \$<installdir>/demo/hspice/sources: *file: sin.spsinusoidal source .options post .param v0=0 va=1 freq=100meg delay=2n theta=5e7 phase=0 v 1 0 sin(v0 va freq delay theta phase) r101 .tran .05n 50n .end Table 13 SIN Voltage Source Parameter Value initial voltage 0 volts pulse voltage 1 volt delay time 2 nanoseconds frequency 100 MHz HSPICE® User Guide: Simulation and Analysis B-2008.09 195 Chapter 9: Sources and Stimuli Independent Source Functions Table 13 SIN Voltage Source Parameter Value damping factor 50 MHz Exponential Source Function HSPICE or HSPICE RF provides a exponential source function, in an independent voltage or current source. Vxxx n+ n- EXP <(> v1 v2 <td1 <t1 <td2 <t2>>>> <)> Ixxx n+ n- EXP <(> v1 v2 <td1 <t1 <td2 <t2>>>> <)> Parameter Description Vxxx, Ixxx Independent voltage source, exhibiting an exponential response. EXP Keyword for an exponential time-varying source. v1 Initial value of voltage or current, in volts or amps. v2 Pulsed value of voltage or current, in volts or amps. td1 Rise delay time, in seconds. Default=0.0. td2 Fall delay time, in seconds. Default=td1+TSTEP. t1 Rise time constant, in seconds. Default=TSTEP. t2 Fall time constant, in seconds. Default=TSTEP. TSTEP is the printing increment, and TSTOP is the final time. 196 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Independent Source Functions The following table of expressions defines the waveform shape: Table 14 Waveform Shape Definitions Time Value 0 to td1 v1 td1 to td2 v1 + (v2 – v1) ⋅ 1 – exp ⎛ – Time – td 1⎞ -------------------------⎝ ⎠ τ 1 td2 to tstop v1 + (v2 – v1) ⋅ 1 – exp ⎛ – ( Time – td 1 )⎞ + ------------------------------⎝ ⎠ τ 1 (v1 – v2) ⋅ ( Time – td 2 ) 1 – exp ⎛ – ------------------------------- ⎞ ⎝ ⎠ τ2 Example VIN 3 0 EXP (-4 -1 2NS 30NS 60NS 40NS) The above example describes an exponential transient source, which connects between nodes 3 and 0. In this source: ■ Initial t=0 voltage is -4 V. ■ Final voltage is -1 V. ■ Waveform rises exponentially from -4 V to -1 V with a time constant of 30 ns. ■ At 60 ns, the waveform starts dropping to -4 V again, with a time constant of 40 ns. HSPICE® User Guide: Simulation and Analysis B-2008.09 197 Chapter 9: Sources and Stimuli Independent Source Functions Figure 20 Exponential Source Function This example is based on demonstration netlist exp.sp, which is available in directory \$installdir/demo/hspice/sources: *file: exp.spexponential independant source .options post .param v0=-4 va=-1 td1=5n tau1=30n tau2=40n td2=80n v 1 0 exp(v0 va td1 tau1 td2 tau2) r101 .tran .05n 200n .end This example shows an entire netlist, which contains an EXP voltage source. In this source: ■ ■ Final voltage is -1 V. ■ Waveform rises exponentially from -4 V to -1 V with a time constant of 30 ns. ■ 198 Initial t=0 voltage is -4 V. At 80 ns, the waveform starts dropping to -4 V again, with a time constant of 40 ns. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Independent Source Functions Piecewise Linear Source HSPICE or HSPICE RF provides a piecewise linear source function, in an independent voltage or current source. General Form Vxxx n+ n- PWL <(> t1 v1 <t2 v2 t3 v3…> <R <=repeat>> + <TD=delay> <)> Ixxx n+ n- PWL <(> t1 v1 <t2 v2 t3 v3…> <R <=repeat>> + <TD=delay> <)> MSINC and ASPEC Form Vxxx n+ n- PL <(> v1 t1 <v2 t2 v3 t3…> <R <=repeat>> + <TD=delay> <)> Ixxx n+ n- PL <(> v1 t1 <v2 t2 v3 t3…> <R <=repeat>> + <TD=delay> <)> Parameter Description Vxxx, Ixxx Independent voltage source; uses a piecewise linear response. PWL Keyword for a piecewise linear time-varying source. v1 v2 … vn Current or voltage values at the corresponding timepoint. t1 t2 … tn Timepoint values, where the corresponding current or voltage value is valid. R=repeat Keyword and time value to specify a repeating function. With no argument, the source repeats from the beginning of the function. repeat is the time, in units of seconds, which specifies the start point of the waveform to repeat. This time needs to be less than the greatest time point, tn. TD=delay Time, in units of seconds, which specifies the length of time to delay (propagation delay) the piecewise linear function. HSPICE® User Guide: Simulation and Analysis B-2008.09 199 Chapter 9: Sources and Stimuli Independent Source Functions ■ Each pair of values (t1, v1) specifies that the value of the source is v1 (in volts or amps), at time t1. ■ Linear interpolation between the time points determines the value of the source, at intermediate values of time. ■ The PL form of the function accommodates ASPEC style formats, and reverses the order of the time-voltage pairs to voltage-time pairs. ■ If you do not specify a time-zero point, HSPICE or HSPICE RF uses the DC value of the source, as the time-zero source value. HSPICE or HSPICE RF does not force the source to terminate at the TSTOP value, specified in the .TRAN statement. If the slope of the piecewise linear function changes below a specified tolerance, the timestep algorithm might not choose the specified time points as simulation time points. To obtain a value for the source voltage or current, HSPICE or HSPICE RF extrapolates neighboring values. As a result, the simulated voltage might deviate slightly from the voltage specified in the PWL list. To force HSPICE or HSPICE RF to use the specified values, use .OPTION SLOPETOL, which reduces the slope change tolerance. R causes the function to repeat. You can specify a value after this R, to indicate the beginning of the function to repeat. The repeat time must equal a breakpoint in the function. For example, if t1=1, t2=2, t3=3, and t4=4, then the repeat value can be 1, 2, or 3. Specify TD=val to cause a delay at the beginning of the function. You can use TD with or without the repeat function. Example This example is based on demonstration netlist pwl.sp, which is available in directory \$<installdir>/demo/hspice/sources: file pwl.sp repeated piecewise linear source .option post .tran 5n 500n v1 1 0 pwl 60n 0v, 120n 0v, 130n 5v, 170n 5v, 180n 0v, r r1 1 0 1 v2 2 0 pl 0v 60n, 0v 120n, 5v 130n, 5v 170n, 0v 180n, r 60n r2 2 0 1 .end This example shows an entire netlist, which contains two piecewise linear voltage sources. The two sources have the same function: 200 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Independent Source Functions ■ First is in normal format. The repeat starts at the beginning of the function. ■ Second is in ASPEC format. The repeat starts at the first timepoint. See Figure 21 for the difference in responses. Figure 21 Results of Using the Repeat Function Data-Driven Piecewise Linear Source HSPICE provides a data-driven piecewise linear source function in an independent voltage or current source. Vxxx n+ n- PWL (TIME, PV) Ixxx n+ n- PWL (TIME, PV) .DATA dataname TIME PV t1 v1 t2 v2 t3 v3 t4 v4 .... .ENDDATA HSPICE® User Guide: Simulation and Analysis B-2008.09 201 Chapter 9: Sources and Stimuli Independent Source Functions .TRAN DATA=datanam Parameter Description TIME Parameter name for time value, provided in a .DATA statement. PV Parameter name for amplitude value, provided in a .DATA statement. Use with a .DATA statement that contains time-value pairs. For each tn-vn (time-value) pair that you specify in the .DATA block, the data-driven PWL function outputs a current or voltage of the specified tn duration and with the specified vn amplitude. This source enables simulation results reuse as an input source in another simulation. Transient analysis must be data-driven. Example This example is based on demonstration netlist datadriven_pwl.sp, which is available in directory \$<installdir>/demo/hspice/sources: *DATA DRIVEN PIECEWISE LINEAR SOURCE .options list node post V1 1 0 PWL(TIME, pv1) R1 1 0 1 V2 2 0 PWL(TIME, pv2) R2 2 0 1 .DATA dsrc TIME pv1 pv2 0n 5v 0v 5n 0v 5v 10n 0v 5v .ENDDATA .TRAN DATA=dsrc .print v(1) v(2) .END This example is an entire netlist, containing two data-driven, piecewise linear voltage sources. The .DATA statement contains the two sets of values referenced in the pv1 and pv2 sources. The .TRAN statement references the data name; there should be no time in .TRAN because time has been included in DATA. Single-Frequency FM Source HSPICE or HSPICE RF provides a single-frequency FM source function, in an independent voltage or current source. 202 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Independent Source Functions Vxxx n+ n- SFFM <(> vo va <fc <mdi <fs>>> <)> Ixxx n+ n- SFFM <(> vo va <fc <mdi <fs>>> <)> Parameter Description Vxxx, Ixxx Independent voltage source, which exhibits the frequencymodulated response. SFFM Keyword for a single-frequency, frequency-modulated, time-varying source. vo Output voltage or current offset, in volts or amps. va Output voltage or current amplitude, in volts or amps. fc Carrier frequency, in Hz. Default=1/TSTOP. mdi Modulation index, which determines the magnitude of deviation from the carrier frequency. Values normally lie between 1 and 10. Default=0.0. fs Signal frequency, in Hz. Default=1/TSTOP. The following expression defines the waveform shape: s ourcevalue = vo + va ⋅ SIN [ 2 ⋅ π ⋅ fc ⋅ Time + mdi ⋅ SIN ( 2 ⋅ π ⋅ fs ⋅ Time ) ] Example This example is based on demonstration netlist sffm.sp, which is available in directory \$<installdir>/demo/hspice/sources: *file: sffm.spfrequency modulation source .options post vsff1 15 0 dc 3v sffm(0v 1v 20k 10 5k) rssf1 15 0 1 .tran .001ms .5ms .probe tran v(15) .end This example shows an entire netlist, which contains a single-frequency, frequency-modulated voltage source. In this source. ■ The offset voltage is 0 volts. ■ The maximum voltage is 1 millivolt. HSPICE® User Guide: Simulation and Analysis B-2008.09 203 Chapter 9: Sources and Stimuli Independent Source Functions ■ The carrier frequency is 20 kHz. ■ The signal is 5 kHz, with a modulation index of 10 (the maximum wavelength is roughly 10 times as long as the minimum). Figure 22 Single Frequency FM Source Single-Frequency AM Source HSPICE or HSPICE RF provides a single-frequency AM source function in an independent voltage or current source. Vxxx n+ n- AM < (> sa oc fm fc <td> <)> Ixxx n+ n- AM < (> sa oc fm fc <td> <)> Parameter Vxxx, Ixxx Independent voltage source, which exhibits the amplitude-modulated response. AM 204 Description Keyword for an amplitude-modulated, time-varying source. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Independent Source Functions sa Signal amplitude, in volts or amps. Default=0.0. fc Carrier frequency, in hertz. Default=0.0. fm Modulation frequency, in hertz. Default=1/TSTOP. oc Offset constant, a unitless constant that determines the absolute magnitude of the modulation. Default=0.0. td Delay time (propagation delay) before the start of the signal, in seconds. Default=0.0. The following expression defines the waveform shape: s ourcevalue = sa ⋅ { + SIN [ 2 ⋅ π ⋅ fm ⋅ ( Time – td ) ] }⋅ SIN [ 2 ⋅ π ⋅ fc ⋅ ( Time – td ) ] oc Example This example is based on demonstration netlist amsrc.sp, which is available in directory \$<installdir>/demo/hspice/sources: *file amsrc.sp amplitude modulation .option post .tran .01m 20m v1 1 0 am(10 1 100 1k 1m) r1 1 0 1 v2 2 0 am(2.5 4 100 1k 1m) r2 2 0 1 v3 3 0 am(10 1 1k 100 1m) r3 3 0 1 .end This example shows an entire netlist, which contains three amplitudemodulated voltage sources. ■ In the first source: • Amplitude is 10. • Offset constant is 1. • Carrier frequency is 1 kHz. • Modulation frequency of 100 Hz. • Delay is 1 millisecond. HSPICE® User Guide: Simulation and Analysis B-2008.09 205 Chapter 9: Sources and Stimuli Independent Source Functions ■ In the second source, only the amplitude and offset constant differ from the first source: • • Offset constant is 4. • Carrier frequency is 1 kHz. • Modulation frequency of 100 Hz. • ■ Amplitude is 2.5. Delay is 1 millisecond. The third source exchanges the carrier and modulation frequencies, compared to the first source: • Amplitude is 10. • Offset constant is 1. • Carrier frequency is 100 Hz. • Modulation frequency of 1 kHz. • Delay is 1 millisecond. Figure 23 206 Amplitude Modulation Plot HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Independent Source Functions Pattern Source HSPICE or HSPICE RF provides a pattern source function, in an independent voltage or current source. The pattern source function uses four states, '1','0','m', and 'z', which represent the high, low, middle voltage, or current and high impedance state respectively. The series of these four states is called a “bstring.” Vxxx n+ n- PAT <(> vhi vlo td tr tf + <R=repeat> <)> tsample data <RB=val> Ixxx n+ n- PAT <(> vhi vlo td tr tf + <R=repeat> <)> tsample data <RB=val> Parameter Description Vxxx, Ixxx Independent voltage source that exhibits a pattern response. PAT Keyword for a pattern time-varying source. vhi High voltage or current value for pattern sources (units of volts or amps). vlo Low voltage or current value for pattern sources (units of volts or amps). td Delay (propagation) time in seconds from the beginning of the transient interval to the first onset ramp. It can be negative. The state in the delay time is the same as the first state specified in data. tr Duration of the onset ramp (in seconds) from the low value to the high value (reverse transit time). tf Duration of the recovery ramp (in seconds) from the high value back to the low value (forward transit time). tsample Time spent at '0' or '1' or 'M' or 'Z' pattern value (in seconds). HSPICE® User Guide: Simulation and Analysis B-2008.09 207 Chapter 9: Sources and Stimuli Independent Source Functions Parameter Description data String of '1' ,'0','M', 'Z' representing a pattern source. The first alphabet must be 'B', which represents it is a binary bit stream. This series is called b-string. '1' represents the high voltage or current value, '0' is the low voltage or current value, 'M' represents the value which is equal to 0.5*(vhi+vlo).'Z' represents the high impedance state (only for voltage source). RB Keyword to specify the starting bit when repeating. The repeat data starts from the bit indicated by RB. RB must be an integer. If the value is larger than the length of the b-string, an error is reported. If the value is less than 1, it is set to 1 automatically. R=repeat Keyword to specify how many times to execute the repeating operation be executed. With no argument, the source repeats from the beginning of the b-string. If R=-1, it means the repeating operation will continue forever. R must be an integer and if it is less than -1, it will be set to 0 automatically. The time from 0 to the first transition is: tdelay+N*tsample-tr(tf)/2 ■ N is the number of the same bit from the beginning. ■ If the first transition is rising, this equation uses tr. ■ If the first transition is falling, it uses tf. Example The following example shows a pattern source with two b-strings: *FILE: pattern source gereral form v1 1 0 pat (5 0 0n 1n 1n 5n b1011 r=1 rb=2 b0m1z) r1 1 0 1 In this pattern: ■ ■ Low voltage is 0 v ■ Time delay is 0 n ■ Rise time is 1 n ■ Fall time is 1 n ■ 208 High voltage is 5 v Sample time is 5 n HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Independent Source Functions The first b-string is 1011, which repeats once and then repeats from the second bit, which is 0. The second b-string is 0m1z. Since neither R and RB is specified here, they are set to the default value, which is R=0, RB=1. Example The following b-string and its repeat time R and repeating start bit RB cannot use a parameter—it is considered as a undivided unit in HSPICE and can only be defined in a .PAT command. *FILE:pattern source using parameter .param td=40ps tr=20ps tf=80ps tsample=400ps VIN 1 0 PAT (2 0 td tr tf tsample b1010110 r=2) r1 1 0 1 In this pattern: ■ High voltage is 2 V. ■ Low voltage is 0 V. ■ Time delay is 40 ps. ■ Rise time is 20 ps. ■ Fall time is 80 ps. ■ Sample time is 400 ps. ■ Data is 1010110. Nested-Structure Pattern Source HSPICE provides Nested Structure (NS) for the pattern source function to construct complex waveforms. NS is a combination of a b-string and other nested structures defined in a .PAT command, which is explained later in this section. The following general syntax is for an NS pattern source. Vxxx n+ n- PAT + [component 1 Ixxx n+ n- PAT + [component 1 <(> ... <(> ... vhi vlo td tr tf tsample component n] <RB=val> <R=repeat> <)> vhi vlo td tr tf tsample component n] <RB=val> <R=repeat> <) > Parameter Description component Component is the element that makes up NS, which can be a b-string or a patname defined in other PAT commands. Brackets ( [ ] ) must be used. HSPICE® User Guide: Simulation and Analysis B-2008.09 209 Chapter 9: Sources and Stimuli Independent Source Functions Parameter Description RB=val Keyword to specify the starting component when repeating. The repeat data starts from the component indicated by RB. RB must be an integer. If RB is larger than the length of the NS, an error is reported. If RB is less than 1, it is automatically set to 1. R=repeat Keyword to specify how many times the repeating operation is executed. With no argument, the source repeats from the beginning of the NS. If R=-1, the repeating operation continues indefinitely. R must be an integer, and if it is less than -1, it is automatically set to 0. If the component is a b-string, it can also be followed by R=repeat and RB=val to specify the repeat time and repeating start bit. Example *FILE: Pattern source using nested structure v1 1 0 pat (5 0 0n 1n 1n 5n [b1011 r=1 rb=2 b0m1z] r=2 rb=2) r1 1 0 1 When expanding the nested structure, you get the pattern source like this: 'b1011 r=1 rb=2 b0m1z b0m1z b0m1z' The whole NS repeats twice, and each time it repeats from the second b0m1z component. Pattern-Command Driven Pattern Source The following general syntax is for including a pattern-command driven pattern source in an independent voltage or current source. The RB and R of a b-string or NS can be reset in an independent source. With no argument, the R and RB are the same when defined in the pattern command. Vxxx n+ n- PAT <(> vhi vlo td tr tf tsample PatName <RB=val> + <R=repeat> <)> Ixxx n+ n- PAT <(> vhi vlo td tr tf tsample Patname <RB=val> + <R=repeat> <)> Additional syntax applies to the .PAT-command driven pattern source: .PAT <PatName>=data <RB=val> <R=repeat> .PAT <patName>=[component 1 ... component n] <RB=val> <R=repeat> 210 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Independent Source Functions The PatName is the pattern name that has an associated b-string or nested structure. Example 1 v1 1 0 pat (5 0 0n 1n 1n 5n a1 a2 r=2 rb=2) .PAT a1=b1010 r=1 rb=1 .PAT a2=b0101 r=1 rb=1 The final pattern source is: b1010 r=1 rb=1 b0101 r=2 rb=2 When the independent source uses the pattern command to specify its pattern source, r and rb can be reset. Example 2 *FILE 2: Pattern source driven by pattern command v1 1 0 pat (5 0 0n 1n 1n 5n [a1 b0011] r=1 rb=1) .PAT a1=[b1010 b0101] r=0 rb=1 The final pattern source is: b1010 b0101 b0011 b1010 b0101 b0011 The a1 is a predefined NS, and it can be referenced by pattern source. Pseudo Random-Bit Generator Source HSPICE or HSPICE RF Pseudo Random Bit Generator Source (PRBS) function, in an independent voltage or current source. This function can be used in several applications from cryptography and bit-error-rate measurement, to wireless communication systems employing spread spectrum or CDMA techniques. In general, PRBS uses a Linear Feedback Shift Register (LFSR) to generate a pseudo random bit sequence. Vxxx n+ n- LFSR <(> vlow vhigh tdelay trise tfall rate seed <[> + taps <]> <rout=val> <)> Ixxx n+ n- LFSR <(> vlow vhigh tdelay trise tfall rate seed <[> + taps <]> <rout=val> <)> Parameter Description LFSR Specifies the voltage or current source as PRBS. HSPICE® User Guide: Simulation and Analysis B-2008.09 211 Chapter 9: Sources and Stimuli Independent Source Functions Parameter Description vlow The minimum voltage or current level. vhigh The maximum voltage or current level. tdelay Specifies the initial time delay to the first transition. trise Specifies the duration of the onset ramp (in seconds) from the initial value to the pulse plateau value (reverse transit time). tfall Specifies the duration of the recovery ramp (in seconds) from the pulse plateau back to the initial value (forward transit time). rate The bit rate. seed The initial value loaded into the shift register. taps The bits used to generate feedback. rout The output resistance. Example 1 The following example shows the pattern source that is connected between node in and node gnd: vin in gnd LFSR (0 1 1m 1n 1n 10meg 1 [5, 2] rout=10) Where, ■ The output low voltage is 0 , and the output high voltage is 1 v. ■ The delay time is 1 ms. ■ The rise and fall times are each 1 ns. ■ The bit rate is 10meg bits/s. ■ The seed is 1. ■ The taps are [5, 2]. ■ The output resistance is 10 ohm. ■ The output from the LFSR is: 1000010101110110001111100110100... Example 2 The following example shows the pattern source connected between node 1 and node 0: 212 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Independent Source Functions .PARAM td1=2.5m tr1=2n vin 1 0 LFSR (2 4 td1 tr1 1n 6meg 2 [10, 5, 3, 2]) Where, ■ The output low voltage is 2 v, and the output high voltage is 4 v. ■ The delay is 2.5 ms. ■ The rise time is 2 ns, and the fall time is 1 ns. ■ The bit rate is 6meg bits/s. ■ The seed is 2. ■ The taps are [10, 5, 3, 2]. ■ The output resistance is 0 ohm. Example 3 This example is based on demonstration netlist prbs.sp, which is available in directory \$installdir/demo/hspice/sources: * prbs.sp .OPTION POST .TRAN 0.5n 50u V1 1 0 LFSR (0 1 1u 1n 1n 10meg 1 [5, 2] rout=10) R1 1 0 1 .END Example 4 To generate a PRBS source that includes jitter, use the following steps: 1. Construct your usual linear feedback shift register (LFSR) generator. 2. Construct a matching (T,tr,tf) PULSE source as a clock, but add jitter to it with the PERJITTER keyword. 3. Use the PULSE source to gate (buffer) the LFSR output (through an ideal AND gate, VCCS, or similar function). Linear Feedback Shift Register A LFSR consists of several simple-shift registers in which a binary-weighted modulo-2 sum of the taps is fed back to the input. The modulo-2 sum of two1bit binary numbers yields 0 if the two numbers are identical and 1 if the differ is 0+0=0, 0+1=1, or 1+1=0. HSPICE® User Guide: Simulation and Analysis B-2008.09 213 Chapter 9: Sources and Stimuli Independent Source Functions g(0) g(1) g(2) g(m-1) g(m) D(n) input D(n-1) Figure 24 D(n-2) D(2) D(1) output LFSR Diagram For any given tap, the weight “gi” is either 0, (meaning “no connection”), or 1, (meaning it is fed back). Two exceptions are g0 and gm, which are always 1 and therefore always connected. The gm is not really a feedback connection, but rather an input of the shift register that is assigned a feedback weight for mathematical purposes. The maximum number of bits is defined by the first number in your TAPS definition. For example [23, 22, 21, 20, 19, 7] denotes a 23 stage LFSR. The TAPS definition is a specific feedback tap sequence that generates an M-Sequence PRB. The LFSR stages limit is between 2 and 30. The seed cannot be set to zero; HSPICE reports an error and exits the simulation if you set the seed to zero. Conventions for Feedback Tap Specification A given set of feedback connections can be expressed in a convenient and easy-to-use shorthand form with the connection numbers listed within a pair of brackets. The g0 connection is implied and not listed since it is always connected. Although gm is also always connected, it is listed in order to convey the shift register size (number of registers). The following line is a set of feedback taps where j is the total number of feedback taps (not including g0), f(1)=m is the highest-order feedback tap (and the size of the LFSR), and f(j) are the remaining feedback taps: [f(1), f(2), f(3), ..., f(j)] Example The following line shows that the number of registers is 7 and the total number of feedback taps is 4: 214 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Voltage and Current Controlled Elements [7, 3, 2, 1] The following feedback input applies for this specification: D(n)=[D(n-7)+D(n-3)+D(n-2)+D(n-1)] mod 2 Voltage and Current Controlled Elements HSPICE or HSPICE RF provides two voltage-controlled and two currentcontrolled elements, known as E, G, H, and F Elements. You can use these controlled elements to model: ■ MOS transistors ■ bipolar transistors ■ tunnel diodes ■ SCRs ■ analog functions, such as: • operational amplifiers • summers • comparators • voltage-controlled oscillators • modulators • switched capacitor circuits Depending on whether you used the polynomial or piecewise linear functions, the controlled elements can be: ■ Linear functions of controlling-node voltages. ■ Non-linear functions of controlling-node voltages. ■ Linear functions of branch currents. ■ Non-linear functions of branch currents. The functions of the E, F, G, and H controlled elements are different. ■ The E-element can be: • A voltage-controlled voltage source • A behavioral voltage source HSPICE® User Guide: Simulation and Analysis B-2008.09 215 Chapter 9: Sources and Stimuli Voltage and Current Controlled Elements • • An ideal transformer. • An ideal delay element. • ■ An ideal op-amp. A piecewise linear, voltage-controlled, multi-input AND, NAND, OR, or NOR gate. The F-element can be: • • An ideal delay element. • ■ A current-controlled current source. A piecewise linear, current-controlled, multi-input AND, NAND, OR, or NOR gate. The G-element can be: • • A behavioral current source. • A voltage-controlled resistor. • A piecewise linear, voltage-controlled capacitor. • An ideal delay element. • ■ A voltage-controlled current source. A piecewise linear, multi-input AND, NAND, OR, or NOR gate. The H-element can be: • A current-controlled voltage source. • An ideal delay element. • A piecewise linear, current-controlled, multi-input AND, NAND, OR, or NOR gate. The next section describes polynomial and piecewise linear functions. Later sections describe element statements for linear or nonlinear functions. For detailed PWL examples, see PWL/DATA/VEC Converter on page 338. Polynomial Functions You can use the controlled element statement to define the controlled output variable (current, resistance, or voltage), as a polynomial function of one or more voltages or branch currents. You can select several polynomial equations, using the POLY(NDIM) parameter in the E, F, G, or H-element statement. 216 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Voltage and Current Controlled Elements Syntax can be either POLY=INTEGER_NUMBER or POLY(INTEGER_NUMBER) For example, either of the following are legitimate statements for an E-element instance with the POLY function: E1 e1 0 POLY=2 e11 0 e12 0 123 or E1 e1 0 POLY(2) e11 0 e12 0 123 Polynomial values can be: Value Description POLY(1) One-dimensional equation (function of one controlling variable). POLY(2) Two-dimensional equation (function of two controlling variables). POLY(3) Three-dimensional equation (function of three controlling variables). POLY(n) Multi-dimensional equation (function of n controlling variables). Each polynomial equation includes polynomial coefficient parameters (P0, P1 … Pn), which you can set to explicitly define the equation. One-Dimensional Function If the function is one-dimensional (a function of one branch current or node voltage), the following expression determines the FV function value: FV = P 0 + ( P 1 ⋅ FA ) + ( P 2 ⋅ FA 2 ) + ( P 3 ⋅ FA 3 ) + ( P 4 ⋅ FA 4 ) + ( P 5 ⋅ FA 5 ) + … Parameter Description FV Controlled voltage or current from the controlled source. P0. . .PN Coefficients of a polynomial equation. FA Controlling branch current, or nodal voltage. HSPICE® User Guide: Simulation and Analysis B-2008.09 217 Chapter 9: Sources and Stimuli Voltage and Current Controlled Elements Note: If you specify one coefficient in a one-dimensional polynomial, HSPICE or HSPICE RF assumes that the coefficient is P1 (P0=0.0). Use this as input for linear controlled sources. The following controlled source statement is a one-dimensional function. This voltage-controlled voltage source connects to nodes 5 and 0. E1 5 0 POLY(1) 3 2 1 2.5 In the above source statement, the single-dimension polynomial function parameter, POLY(1), informs HSPICE or HSPICE RF that E1 is a function of the difference of one nodal voltage pair. In this example, the voltage difference is between nodes 3 and 2, so FA=V(3,2). The dependent source statement then specifies that P0=1 and P1=2.5. From the one-dimensional polynomial equation above, the defining equation for V(5,0) is: V ( 5, 0 ) = 1 + 2.5 ⋅ V (3,2) You can also express V(5,0) as E1: E 1 = 1 + 2.5 ⋅ V (3,2) Two-Dimensional Function If the function is two-dimensional (that is, a function of two node voltages or two branch currents), the following expression determines FV: 2 2 FV = P 0 + ( P 1 ⋅ FA ) + ( P 2 ⋅ FB ) + ( P 3 ⋅ FA ) + ( P 4 ⋅ FA ⋅ FB ) + ( P 5 ⋅ FB ) 3 2 2 3 + ( P 6 ⋅ FA ) + ( P 7 ⋅ FA ⋅ FB ) + ( P 8 ⋅ FA ⋅ FB ) + ( P 9 ⋅ FB ) + ... For a two-dimensional polynomial, the controlled source is a function of two nodal voltages or currents. To specify a two-dimensional polynomial, set POLY(2) in the controlled source statement. For example, generate a voltage-controlled source that specifies the controlled voltage, V(1,0), as: V ( 1, 0 ) = 3 ⋅ V (3,2) + 4 ⋅ V (7,6) 2 or E 1 = 3 ⋅ V (3,2) + 4 ⋅ V (7,6) 2 To implement this function, use this controlled-source element statement: 218 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Voltage and Current Controlled Elements E1 1 0 POLY(2) 3 2 7 6 0 3 0 0 0 4 This example specifies a controlled voltage source, which connects between nodes 1 and 0. Two differential voltages control this voltage source: ■ Voltage difference between nodes 3 and 2. ■ Voltage difference between nodes 7 and 6. That is, FA=V(3,2), and FB=V(7,6). The polynomial coefficients are: ■ P0=0 ■ P1=3 ■ P2=0 ■ P3=0 ■ P4=0 ■ P5=4 Three-Dimensional Function For a three-dimensional polynomial function, with FA, FB, and FC as its arguments, the following expression determines the FV function value: FV = P 0 + ( P 1 ⋅ FA ) + ( P 2 ⋅ FB ) + ( P 3 ⋅ FC ) + ( P 4 ⋅ FA 2 ) + ( P 5 ⋅ FA ⋅ FB ) + ( P 6 ⋅ FA ⋅ FC ) + ( P 7 ⋅ FB 2 ) + ( P 8 ⋅ FB ⋅ FC ) + ( P 9 ⋅ FC 2 ) + ( P 10 ⋅ FA 3 ) + ( P 11 ⋅ FA 2 ⋅ FB ) + ( P 12 ⋅ FA 2 FC ) + ( P 13 ⋅ FA ⋅ FB 2 ) + ( P 14 ⋅ FA ⋅ FB ⋅ FC ) + ( P 15 ⋅ FA ⋅ FC 2 ) + ( P 16 ⋅ FB 3 ) + ( P 17 ⋅ FB 2 ⋅ FC ) + ( P 18 ⋅ FB ⋅ FC 2 ) + ( P 19 ⋅ FC 3 ) + ( P 20 ⋅ FA 4 ) + … For example, generate a voltage-controlled source that specifies the voltage as: V ( 1, 0 ) = 3 ⋅ V (3,2) + 4 ⋅ V (7,6) 2 + 5 ⋅ V (9,8) 3 or E 1 = 3 ⋅ V (3,2) + 4 ⋅ V (7,6) 2 + 5 ⋅ V (9,8) 3 The resulting three-dimensional polynomial equation is: FA = V (3,2) FB = V (7,6) HSPICE® User Guide: Simulation and Analysis B-2008.09 219 Chapter 9: Sources and Stimuli Voltage and Current Controlled Elements FC = V (9,8) P1 = 3 P7 = 4 P 19 = 5 Substitute these values into the voltage controlled voltage source statement: E1 1 0 POLY(3) 3 2 7 6 9 8 0 3 0 0 0 0 0 4 0 0 0 0 0 0 +000005 The preceding example specifies a controlled voltage source, which connects between nodes 1 and 0. Three differential voltages control this voltage source: ■ Voltage difference between nodes 3 and 2. ■ Voltage difference between nodes 7 and 6. ■ Voltage difference between nodes 9 and 8. That is: ■ FA=V(3,2) ■ FB=V(7,6) ■ FC=V(9,8) The statement defines the polynomial coefficients as: ■ P1=3 ■ P7=4 ■ P19=5 ■ Other coefficients are zero. N-Dimensional Function An N-dimensional polynomial function can be expressed as: k FV = p 0 + ∑( pij Fx1 + p2 j Fx2 + ____ + pij Fxk ) j j–1 where, Fx 1 , F x 2 , … … k ,represent the k independent controlling branch …F current, or nodal voltage, and p ij , i = 1, 2, … k = 1, 2, … n are the … … coefficients. 220 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Power Sources Piecewise Linear Function You can use the one-dimensional piecewise linear (PWL) function to model special element characteristics, such as those of: ■ tunnel diodes ■ silicon-controlled rectifiers ■ diode breakdown regions To describe the piecewise linear function, specify measured data points. Although data points describe the device characteristic, HSPICE or HSPICE RF automatically smooths the corners, to ensure derivative continuity. This, in turn, results in better convergence. The DELTA parameter controls the curvature of the characteristic at the corners. The smaller the DELTA, the sharper the corners are. The maximum DELTA is limited to half of the smallest breakpoint distance. If the breakpoints are sufficiently separated, specify the DELTA to a proper value. ■ You can specify up to 100 point pairs. ■ You must specify at least two point pairs (each point consists of an x and a y coefficient). To model bidirectional switch or transfer gates, G-elements use the NPWL and PPWL functions, which behave the same way as NMOS and PMOS transistors. You can also use the piecewise linear function to model multi-input AND, NAND,OR, and NOR gates. In this usage, only one input determines the state of the output. ■ In AND and NAND gates, the input with the smallest value determines the corresponding output of the gates. ■ In OR and NOR gates, the input with the largest value determines the corresponding output of the gates. Power Sources This section describes independent sources and controlled sources. HSPICE® User Guide: Simulation and Analysis B-2008.09 221 Chapter 9: Sources and Stimuli Power Sources Independent Sources A power source is a special kind of voltage or current source, which supplies the network with a pre-defined power that varies by time or frequency. The source produces a specific input impedance. To apply a power source to a network, you can use either: ■ A Norton-equivalent circuit (if you specify this circuit and a current source)— the I (current source) element, or ■ A Thevenin-equivalent circuit (if you specify this circuit and a voltage source)—the V (voltage source) element. As with other independent sources, simulation assumes that positive current flows from the positive node, through the source, to the negative node. A power source is a time-variant or frequency-dependent utility source; therefore, the value/phase can be a function of either time or frequency. A power source is a subclass of the independent voltage/current source, with some additional keywords or parameters: ■ You can use I and V elements in DC, AC, and transient analysis. The I and V elements can be data-driven. Supported formats include: ■ PULSE, a trapezoidal pulse function. ■ PWL, a piecewise linear function, with repeat function. ■ PL, a piecewise linear function. PWL and PL are the same piecewise linear function, except PL uses the v1 t1 pair instead of the t1 v1 pair. ■ SIN, a damped sinusoidal function. ■ EXP, an exponential function. ■ SFFM, a single-frequency FM function. ■ AM, an amplitude-modulation function. Using the Keyword POWER If you use the POWERkeyword in the netlist, then a simulation recognizes a current/voltage source as a power source: Vxxx node+ node- power=<powerVal <powerFun>> imp=value1 + imp_ac=value2,value3 powerFun=<FREQ <TIME>>(...) Ixxx node+ node- power=<powerVal <powerFun>> imp=value1 222 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Power Sources + imp_ac=value2,value3 powerFun=<FREQ <TIME>>(...) Parameter Description powerVal A constant power source supplies the available power. If you specify POWER_DB, then the value is in decibels; otherwise, it is in Watts*POWER_SCAL, where POWER_SCAL is a scaling factor that you specify in a SCALE option (default=1). powerFun This function name indicates the time-variant or frequency-variant power source. In this equation, powerFun defines the functional dependence on time or frequency. ■ ■ If the function name for powerFun is FREQ, then it is a frequency power source: FREQ(freq1, val1, freq2, val2,...) If the function name for powerFun is TIME, then it is a piece-wise time variant function: TIME(t1, val1, t2, val2...) imp= DC impedance value. imp_ac= Magnitude and phase offset (in degrees) of AC impedance. Example 1 V11 10 20 power=5 imp=5K This example applies a 5-decibel/unit power source to node 10 and node 20, in a Thevenin-equivalent manner. The impedance of this power source is 5k Ohms. Example 2 Iname 1 0 power=20 imp=9MEG This example applies a 20-decibel/unit power source to node 1 and to ground, in a Norton-equivalent manner. The source impedance is 9 mega-ohms. Example 3 V5 6 0 power=FREQ(10HZ, 2, 10KHZ, 0.01) imp=2MEG imp_ac=(100K, 60) V5 6 0 power=func1 imp=2MEG imp_ac=(100K, 60DEC) + func1=FREQ(10HZ, 2, 10KHZ, 0.01) In the two preceding examples, a power source operates at two different frequencies, with two different values: ■ At 10 Hz, the power value is 2 decibel/unit. ■ At 10 kHz, the power value is 0.01 decibel/unit. HSPICE® User Guide: Simulation and Analysis B-2008.09 223 Chapter 9: Sources and Stimuli Power Sources Also in these examples: ■ The DC impedance is 2 mega-ohms. ■ The AC impedance is 100 kilo-ohms. ■ The phase offset is 60 degrees. Power Calculation The POWER keyword is used to calculate the total dissipated power of the circuit. For example, if you have a top level circuit as follows: ******************************** vvdd vdd 0 5 vin in 0 pulse(0 5 0 1n 1n 4n 10n) rout out 0 10k cout out 0 cload x1 in out inv .subckt inv in out mn out in 0 0 nch W=10u L=1u mp out in vdd vdd pch W=10u L=1u .ends ******************************** ...you need to use .PRINT TRAN POWER to calculate the total circuit power. The total circuit POWER will be p(rout)+p(cout)+p(x1). This can also be verified in HSPICE with the following statement, .print tran tot_pwr=par('(p(rout)+p(cout)+p(x1))') Note that HSPICE does not add the power of each independent source (V & I). Subcircuit Power Calculation To print or probe an element or subcircuit power, use the variables, P(element_name) or P(instance_name_of_subckt). For example, if you have the following subcircuit: x1 in out inv .subckt inv in out mn out in 0 0 nch W=10u L=1u mp out in vdd vdd pch W=10u L=1u .ends 224 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Voltage-Dependent Voltage Sources — E-elements ...you can use .PRINT TRAN P(x1) to calculate the subcircuit power. The subcircuit power of P(x1) will be the sum of p(x1.mn) and p(x1.mp). This can be verified by using the following statement: .print tran p_x1=par('p(x1.mn)+p(x1.mp)') Measuring Leakage Power When you probe P(Instance_name), beginning with HSPICE version A2007.12, HSPICE includes the gate tunneling current in the power function calculations. In prior releases, the power calculation function in HSPICE did not include gate tunneling induced power dissipation. Troubleshooting Differences in Rise/Fall Power Input Signals You may note a difference between the AVG power calculations for the rise time and fall time for input signals. There should not be a difference, but if you measure the AVG subcircuit power by using P(Instance_name) for an inverter subcircuit, for example, you may note that HSPICE excludes the energy stored in the output and includes the energy discharged from the capacitor for fall time. If there is any difference in the measured results, then try running the simulation with the most accurate settings by setting .OPTION RUNLVL=6. In addition, you can set .OPTION DELMAX to the minimum rise or fall time of your circuit. Controlled Sources In addition to independent power sources, you can also create four types of controlled sources: ■ Voltage-controlled voltage source (VCVS), or E-element ■ Current-controlled current source (CCCS), or F-element ■ Voltage-controlled current source (VCCS), or G-element ■ Current-controlled voltage source (CCVS), or H-element Voltage-Dependent Voltage Sources — E-elements This section explains E-element syntax statements, and defines their parameters. HSPICE® User Guide: Simulation and Analysis B-2008.09 225 Chapter 9: Sources and Stimuli Voltage-Dependent Voltage Sources — E-elements Exxx n+ n- [VCCS|LEVEL=0] in+ in- ... ■ LEVEL=0 is an interchangeable function keyword, such as VCAP or VCCS, etc. ■ LEVEL=1 is an OpAmp. ■ LEVEL=2 is a Transformer. See also Using G- and E-elements in Chapter 29, Modeling Filters and Networks. Voltage-Controlled Voltage Source (VCVS) Linear Exxx n+ n- [VCVS] in+ in- gain [MAX=val] [MIN=val] + [SCALE=val] [TC1=val] [TC2=val] [ABS=1] [IC=val] For a description of these parameters, see E-element Parameters on page 233. Polynomial (POLY) Exxx n+ n- [VCVS] POLY(NDIM) in1+ in1- ... + inndim+ inndim-TC1=val [TC2=val] [SCALE=val] + [MAX=val] [MIN=val] [ABS=1] p0 p1… [IC=val] In this syntax, dim (dimensions) ≤3. For a description of these parameters, see E-element Parameters on page 233. For a description of possible POLY syntaxes, see Polynomial Functions on page 216. Piecewise Linear (PWL) Exxx n+ n- [VCVS] PWL(1) in+ in- [DELTA=val] + [SCALE=val] [TC1=val] [TC2=val] x1,y1 x2,y2 + x100,y100 [IC=val] ... For a description of these parameters, see E-element Parameters on page 233. Multi-Input Gates Exxx n+ n- [VCVS] gatetype(k) in1+ in1- ... inj+ inj+ [DELTA=val] [TC1=val] [TC2=val] [SCALE=val] + x1,y1 ... x100,y100 [IC=val] 226 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Voltage-Dependent Voltage Sources — E-elements In this syntax, gatetype(k) can be AND, NAND, OR, or NOR gates. For a description of these parameters, see E-element Parameters on page 233. Delay Element Exxx n+ n- [VCVS] DELAY in+ in- TD=val [SCALE=val> + [TC1=val] [TC2=val] [NPDELAY=val] For a description of these parameters, see E-element Parameters on page 233. Laplace Transform Voltage Gain H(s): Exxx n+ n- LAPLACE in+ in- k0, k1, ..., kn / d0, d1, ..., dm + [SCALE=val] [TC1=val] [TC2=val] For a description of these parameters, see E-element Parameters on page 233. Transconductance H(s): Gxxx n+ n- LAPLACE in+ in- k0, k1, ..., kn / d0, d1, ..., dm + [SCALE=val] [TC1=val] [TC2=val] [M=val] H(s) is a rational function, in the following form: k 0 + k 1 s + …+ k n s n H ( s ) = -----------------------------------------------d 0 + d 1 s + …+ d m s m You can use parameters to define the values of all coefficients (k0, k1, ..., d0, d1, ...). For a description of the G-element parameters, see G-element Parameters on page 250. Example Glowpass 0 out LAPLACE in 0 1.0 / 1.0 2.0 2.0 1.0 Ehipass out 0 LAPLACE in 0 0.0,0.0,0.0,1.0 / 1.0,2.0,2.0,1.0 The Glowpass element statement describes a third-order low-pass filter, with the transfer function: 1 H ( s ) = ---------------------------------------1 + 2s + 2 s2 + s3 The Ehipass element statement describes a third-order high-pass filter, with the transfer function: HSPICE® User Guide: Simulation and Analysis B-2008.09 227 Chapter 9: Sources and Stimuli Voltage-Dependent Voltage Sources — E-elements s3 H ( s ) = ---------------------------------------1 + 2s + 2 s2 + s3 Pole-Zero Function Voltage Gain H(s): Exxx n+ n- POLE in+ in- a az1, fz1, ..., azn, fzn / b, + ap1, fp1, ..., apm, fpm <SCALE=val> <TC1=val> + <TC2=val> For a description of these parameters, see E-element Parameters on page 233. Transconductance H(s): Gxxx n+ n- POLE in+ in- a az1, fz1, ..., azn, fzn / b, + ap1, fp1, ..., apm, fpm <SCALE=val> <TC1=val> + <TC2=val> <M=val> The following equation defines H(s) in terms of poles and zeros: ( a ⋅ ( s + αz 1 – j 2 π f z 1 )… s + αzn – j 2 πf zn ) ( s + αzn + j 2 πf zn ) H ( s ) = ---------------------------------------------------------------------------------------------------------------------------------------------------b ⋅ ( s + αp 1 – j 2 π f p 1 )… s + αpm – j 2 π f pm ) ( s + αpm + j 2 π f pm ) ( The complex poles or zeros are in conjugate pairs. The element description specifies only one of them, and the program includes the conjugate. You can use parameters to specify the a, b, α, and f values. For a description of the G-element parameters, see G-element Parameters on page 250. Example Ghigh_pass 0 out POLE in 0 1.0 0.0,0.0 / 1.0 0.001,0.0 Elow_pass out 0 POLE in 0 1.0 / 1.0, 1.0,0.0 0.5,0.1379 The Ghigh_pass statement describes a high-pass filter, with the transfer function: 1.0 ⋅ ( s + 0.0 + j ⋅ 0.0 ) H ( s ) = --------------------------------------------------------------1.0 ⋅ ( s + 0.001 + j ⋅ 0.0 ) The Elow_pass statement describes a low-pass filter, with the transfer function: 1.0 H ( s ) = ----------------------------------------------------------------------------------------------------------------------------------------------------------1.0 ⋅ ( s + 1 ) ( s + 0.5 + j 2 π ⋅ 0.1379 ) ( s + 0.5 – ( j 2 π ⋅ 0.1379 ) ) 228 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Voltage-Dependent Voltage Sources — E-elements Frequency Response Table Voltage Gain H(s): Exxx n+ n- FREQ in+ in- f1, a1, f1, ..., fi, ai, f1 + <DELF=val> <MAXF=val> <SCALE=val> <TC1=val> + <TC2=val> <LEVEL=val> <ACCURACY=val> For a description of these parameters, see E-element Parameters on page 233 Transconductance H(s): Gxxx n+ n- FREQ in+ in- f1, a1, f1, ..., fi, ai, f1 + <DELF=val> <MAXF=val> <SCALE=val> <TC1=val> + <TC2=val> <M=val> <LEVEL=val> <ACCURACY=val> Where, ■ Each fi is a frequency point, in hertz. ■ ai is the magnitude, in dB. ■ f1 is the phase, in degrees. At each frequency, HSPICE or HSPICE RF uses interpolation to calculate the network response, magnitude, and phase. HSPICE or HSPICE RF interpolates the magnitude (in dB) logarithmically, as a function of frequency. It also interpolates the phase (in degrees) linearly, as a function of frequency. ai – ak H ( j 2 πf ) = ⎛ ---------------------------- ⎞ ( log f – log f i ) + a i ⎝ log f i – log f k⎠ φi – φk ∠H ( j 2 π f ) = ⎛ ------------- ⎞ ( f – f i ) + φi ⎝ fi – fk ⎠ For a description of the G-element parameters, see G-element Parameters on page 250. Example Eftable output + 1.0k -3.97m + 2.0k -2.00m + 3.0k 17.80m + ...... ... + 10.0k -53.20 0 FREQ input 293.7 211.0 82.45 0 -1125.5 HSPICE® User Guide: Simulation and Analysis B-2008.09 229 Chapter 9: Sources and Stimuli Voltage-Dependent Voltage Sources — E-elements ■ The first column is frequency, in hertz. ■ The second column is magnitude, in dB. ■ The third column is phase, in degrees. Set the LEVEL to 1 for a high-pass filter. Set the last frequency point to the highest frequency response value that is a real number, with zero phase. You can use parameters to set the frequency, magnitude, and phase, in the table. Foster Pole-Residue Form Gain E(s) form Exxx n+ n+ (Re{A1}, + (Re{A2}, + (Re{A3}, + ... FOSTER in+ in- k0 Im{A1})/ (Re{p1}, Im{A2})/ (Re{p2}, Im{A3})/ (Re{p3}, k1 Im{p1}) Im{p2}) Im{p3}) For a description of these parameters, see E-element Parameters on page 233. Transconductance G(s) form Gxxx n+ n+ (Re{A1}, + (Re{A2}, + (Re{A3}, + ... FOSTER in+ in- k0 Im{A1})/ (Re{p1}, Im{A2})/ (Re{p2}, Im{A3})/ (Re{p3}, k1 Im{p1}) Im{p2}) Im{p3}) In the above syntax, parenthesis , commas, and slashes are separators—they have the same meaning as a space. A pole-residue pair is represented by four numbers (real and imaginary part of the residue, then real and imaginary part of the pole). You must make sure that Re[pi]<0; otherwise, the simulations will certainly diverge. Also, it is a good idea to assure passivity of the model (for an N-port admittance matrix Y, Re{Y} should be positive-definite), or the simulation is likely to diverge). For a description of the G-element parameters, see G-element Parameters on page 250. Example To represent a G(s) in the form, 230 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Voltage-Dependent Voltage Sources — E-elements ( 0.001 – j 0.006 ) 0.0008 s + ---------------------------- + -------------------------------------------------------------------- + 10 8 10 s – ( – 1 × 10 + j 1.8 × 10 ) s + 1 × 10 ( 0.001 + j 0.006 ) ------------------------------------------------------------------8 10 s – ( – 1 × 10 – j 1.8 × 10 ) G ( s ) = 0.001 + 1 × 10 – 12 You would input: G1 1 0 FOSTER 2 0 0.001 1e-12 +(0.0004, 0)/(-1e10, 0) (0.001, -0.006)/(-1e8, 1.8e10) Note: In the case of a real poles, half the residue value is entered because it is essentially applied twice. In the above example, the first pole-residue pair is real, but is written as “A1/(s-p1)+A1/(s-p1)”; therefore, 0.0004 is entered rather than 0.0008. Behavioral Voltage Source (Noise Model) You can implement a behavioral voltage noise source with an E-element. As noise elements, these are two-terminal elements that represent a noise source connected between two specified nodes. Exxx n+ n- noise=’expression’ Where, Exxx is the voltage-controlled element name, which must being with “E”, followed by up to 1023 alphanumeric characters. n+ is the positive node. n- is the negative node. noise=’expression’ can contain the bias, frequency, or other parameters. Data form Exxx n+ n- noise data=dataname .DATA dataname + pname1 pname2 + freq1 noise1 + freq2 noise2 + ... .enddata The data form defines a basic frequency-noise table. The .DATA statement contains two parameters: frequency and noise to specify the noise value at HSPICE® User Guide: Simulation and Analysis B-2008.09 231 Chapter 9: Sources and Stimuli Voltage-Dependent Voltage Sources — E-elements each frequency point. The unit for frequency is hertz, and the unit for noise is V2/Hz. Ideal Op-Amp Exxx n+ n- OPAMP in+ inYou can also substitute LEVEL=1 in place of OPAMP: Exxx n+ n- in+ in- level=1 For a description of these parameters, see E-element Parameters. Ideal Transformer Exxx n+ n- TRANSFORMER in+ in- k You can also substitute LEVEL=2 in place of TRANSFORMER: Exxx n+ n- in+ in- level=2 k For a description of these parameters, see E-element Parameters. VCVS (op-amp) with Gain = g + V2 V1 Equivalent HSPICE model <=> V2 V2=g*V2 Ideal transformer with ratio K I1 V1 Figure 25 232 + - V1 k:1 .. Equivalent HSPICE model I2 I1 I2 V2 <=> V1 I1=k*I2 + - V2 V1=k*V2 Equivalent VCVS and Ideal Transformer HSPICE Models HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Voltage-Dependent Voltage Sources — E-elements E-element Parameters The E-element parameters are described in the following list. Parameter Description ABS Output is an absolute value, if ABS=1. DELAY Keyword for the delay element. Same as for the voltage-controlled voltage source, except it has an associated propagation delay, TD. This element adjusts propagation delay in macro (subcircuit) modeling. DELAY is a reserved word; do not use it as a node name. DELTA Controls the curvature of the piecewise linear corners. This parameter defaults to one-fourth of the smallest distance between breakpoints. The maximum is one-half of the smallest distance between breakpoints. Exxx Voltage-controlled element name. Must begin with E, followed by up to 1023 alphanumeric characters. gain Voltage gain. gatetype(k) Can be AND, NAND, OR, or NOR. k represents the number of inputs of the gate. x and y represent the piecewise linear variation of output, as a function of input. In multi-input gates, only one input determines the state of the output. IC Initial condition: initial estimate of controlling voltage value(s). If you do not specify IC, default=0.0. in +/- Positive or negative controlling nodes. Specify one pair for each dimension. k Ideal transformer turn ratio: V(in+,in-) = k ⋅ V(n+,n-) or, number of gates input. MAX Maximum output voltage value. The default is undefined, and sets no maximum value. MIN Minimum output voltage value. The default is undefined, and sets no minimum value. HSPICE® User Guide: Simulation and Analysis B-2008.09 233 Chapter 9: Sources and Stimuli Voltage-Dependent Voltage Sources — E-elements Parameter Description n+/- Positive or negative node of a controlled element. NDIM Number of polynomial dimensions. If you do not set POLY(NDIM), HSPICE or HSPICE RF assumes a one-dimensional polynomial. NDIM must be a positive number. NPDELAY Sets the number of data points to use in delay simulations. The default value is the larger of either 10, or the smaller of TD/tstep and tstop/tstep. That is, min 〈 TD, tstop〉 NPDELAY default = max -------------------------------------------, 10 tstep The .TRAN statement specifies tstep and tstop values. LEVEL=<x> Interchangeable function keyword such as VCCS, VCAP, etc. OPAMP or Level=1 The keyword for an ideal op-amp element. OPAMP is a HSPICE reserved word; do not use it as a node name. P0, P1 … The polynomial coefficients. If you specify one coefficient, HSPICE or HSPICE RF assumes that it is P1 (P0=0.0), and that the element is linear. If you specify more than one polynomial coefficient, the element is nonlinear, and P0, P1, P2 ... represent them (see Polynomial Functions on page 216). POLY Keyword for the polynomial function. If you do not specify POLY(ndim), HSPICE assumes a one-dimensional polynomial. Ndim must be a positive number. PWL Keyword for the piecewise linear function. SCALE Multiplier for the element value. TC1,TC2 First-order and second-order temperature coefficients. Temperature changes update the SCALE: SCALEeff = SCALE ⋅ ( 1 + TC 1 ⋅ Δ t + TC 2 ⋅ Δ t 2 ) TD 234 Keyword for the time (propagation) delay. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Voltage-Dependent Voltage Sources — E-elements Parameter Description TRANSFORMER or LEVEL=2 Keyword for an ideal transformer. TRANSFORMER is a reserved word; do not use it as a node name. VOL Voltage output that flows from n+ to n-. The expression that you define can be a function of: ■ ■ ■ ■ ■ node voltages branch currents time (time variable) temperature (temper variable) frequency (hertz variable) VCVS Keyword for a voltage-controlled voltage source. VCVS is a reserved word; do not use it as a node name. x1,... Controlling voltage across the in+ and in- nodes. The x values must be in increasing order. y1,... Corresponding element values of x. E-element Examples Ideal OpAmp You can use the voltage-controlled voltage source to build a voltage amplifier, with supply limits. ■ The output voltage across nodes 2,3 is v(14,1) * 2. ■ The value of the voltage gain parameter is 2. ■ The MAX parameter sets a maximum E1 voltage of 5 V. ■ The MIN parameter sets a minimum E1 voltage output of -5 V. Example If V(14,1)=-4V, then HSPICE or HSPICE RF sets E1 to -5V, and not -8V as the equation suggests. Eopamp 2 3 14 1 MAX=+5 MIN=-5 2.0 To specify a value for polynomial coefficient parameters, use the following format: HSPICE® User Guide: Simulation and Analysis B-2008.09 235 Chapter 9: Sources and Stimuli Voltage-Dependent Voltage Sources — E-elements .PARAM CU=2.0 E1 2 3 14 1 MAX=+5 MIN=-5 CU Voltage Summer An ideal voltage summer specifies the source voltage, as a function of three controlling voltage(s): ■ V(13,0) ■ V(15,0) ■ V(17,0) To describe a voltage source, the voltage summer uses this value: V (13,0) + V (15,0) + V (17,0) This example represents an ideal voltage summer. It initializes the three controlling voltages for a DC operating point analysis, to 1.5, 2.0, and 17.25 V. EX 17 0 POLY(3) 13 0 15 0 17 0 0 1 1 1 IC=1.5,2.0,17.25 Polynomial Function A voltage-controlled source can also output a non-linear function, using a onedimensional polynomial. This example does not specify the POLY parameter, so HSPICE or HSPICE RF assumes it is a one-dimensional polynomial—that is, a function of one controlling voltage. The equation corresponds to the element syntax. Behavioral equations replace this older method. V (3,4)=10.5 + 2.1 *V(21,17) + 1.75 *V(21,17)2” E2 3 4 POLY 21 17 10.5 2.1 1.75 E2 3 4 VOLT=“10.5 + 2.1 *V(21,17) + 1.75 *V(21,17)2” E2 3 4 POLY 21 17 10.5 2.1 1.75 Zero-Delay Inverter Gate Use a piecewise linear transfer function to build a simple inverter, with no delay. Einv out 0 PWL(1) in 0 .7v,5v 1v,0v Delayed and Inverted Signal You can use an E-element to invert a signal to generate a signal which is delayed and the inverse of another signal. Use the following syntax to generate a signal which is delayed (TD) and is the inverse of the input signal (in). 236 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Voltage-Dependent Voltage Sources — E-elements .option list node post Vin in 0 pwl(0 0 10n 0 13n 2v 23n 2v 24n 0v) \$\$ input signal to be inverted and delayed Edelay in_delay 0 DELAY in 0 TD=2n \$\$ signal "in_delay" is the "in" signal delayed by TD Edelay_inv out_inv 0 PWL(1) in1 0 0v 2v 2v 0v \$\$ signal "out_inv" is the inverted and delayed "in" signal .tran .1n 30n .print v(in_delay) v(out_inv) v(in) .end Differential Amplifiers and Opamp Signals Defining a differential voltage source to use with differential amplifiers or opamps can be achieved with E-elements. E-elements can be used to provide differential signals to drive circuits requiring differential signals. ******spice definition***** VID 7 0 DC 0 ac=1 SIN (0 0.70 1MEG) E+ in+ 10 7 0 0.5 \$ differential signal 1, level can be varied by changing gain E- in- 10 7 0 -0.5 \$ differential signal 2 VIC 10 0 DC 0.3V \$VIC is the common mode signal source For a full netlist differential block analysis example, see also: \$installdir/demo/hspice/behave/diff1.sp. Ideal Transformer If the turn ratio is 10 to 1, the voltage relationship is V(out)=V(in)/10. Etrans out 0 TRANSFORMER in 0 10 You can also substitute LEVEL=2 in place of TRANSFORMER: Etrans out 0 in 0 level=2 10 Voltage-Controlled Oscillator (VCO) The VOL keyword defines a single-ended input, which controls output of a VCO. Example 1 In this example, the voltage at the control node controls the frequency of the sinusoidal output voltage at the out node. v0 is the DC offset voltage, and gain is the amplitude. The output is a sinusoidal voltage, whose frequency is specified in freq · control. Evco out 0 VOL=’v0+gain*SIN(6.28 freq*v(control)*TIME)’ HSPICE® User Guide: Simulation and Analysis B-2008.09 237 Chapter 9: Sources and Stimuli Voltage-Dependent Voltage Sources — E-elements Note: This equation is valid only for a steady-state VCO (fixed voltage). If you sweep the control voltage, this equation does not apply. Example 2 In this example, a Verilog-A module is used to control VCO output by tracking phase to ensure continuity. `include "disciplines.vams" module vco(vin, vout); inout vin, vout; electrical vin, vout; parameter real amp = 1.0; parameter real offset = 1.0; parameter real center_freq = 1G; parameter real vco_gain = 1G; real phase; analog begin phase = idt(center_freq + vco_gain*V(vin), 0.0); V(vout) <+ offset+amp*sin(6.2831853*phase); end endmodule Example 3 This example is a controlled-source equivalent of the Verilog-A module shown in the previous example. Like the previous example, it establishes a continuous phase and therefore, a continuous output voltage. .subckt vco in out amp=1 offset=1 center_freq=1 vco_gain=1 .ic v(phase)=0 cphase phase 0 1e-10 g1 0 phase cur='1e-10*(center_freq+vco_gain*v(in))' eout out 0 vol='offset+amp*sin(6.2831853*v(phase))' .ends Example 4 In this example, controlled-sources are used to control VCO output. 238 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Voltage-Dependent Voltage Sources — E-elements .param pi=3.1415926 .param twopi='2*pi' .subckt vco in inb out outb f0=100k kf=50k out_off=0.0 out_amp=1.0 gs 0 s poly(2) c 0 in inb 0 'twopi*1e-9*f0' 0 0 'twopi*1e-9*kf' gc c 0 poly(2) s 0 in inb 0 'twopi*1e-9*f0' 0 0 'twopi*1e-9*kf' cs s 0 1e-9 ic=0 cc c 0 1e-9 ic=1 eout out 0 vol='out_off+(out_amp*v(s))' eoutb outb 0 vol='out_off+(out_amp*v(c))' .ic v(c)=1 v(s)=0 .ends Using the E-element for AC Analysis The following equation describes an E-element: E1 ee 0 vol=f(v(1), v(2)) In an AC analysis, voltage is computed as follows: v(ee)=A * delta_v1 + B * delta_v2 Where, ■ A is the derivative of f(v(1), v(2)) to v(1) at the operating point ■ B is the derivative of f(v(1), v(2)) to v(2) at the operating point ■ delta_v1 is the AC voltage variation of v(1) ■ delta_v2 is the AC voltage variation of v(2) Example This example is based on demonstration netlist eelm.sp, which is available in directory \$<installdir>/demo/hspice/sources: HSPICE® User Guide: Simulation and Analysis B-2008.09 239 Chapter 9: Sources and Stimuli Current-Dependent Current Sources — F-elements ***************************************************** ****** E element for AC analysis .option post .op *CASE1-Mixed and zero time unit has zero value(tran) v_n1 n1 gnd dc=6.0 pwl 0.0 6.0 1.0n 6.0 ac 5.0 v_n2 n2 gnd dc=4.0 pwl 0.0 4.0 1.0n 6.0 ac 2.0 e1 n3 gnd vol='v(n1)+v(n2)' e2 n4 gnd vol='v(n1)*v(n2)' r1 n1 gnd 1 r2 n2 gnd 1 r3 n3 gnd 1 r4 n4 gnd 1 .tran 10p 3n .ac dec 1 1 100meg .print ac v(n?) .end ***************************************************** The AC voltage of node n3 is: v(n3)=1.0 *v(n1)(ac) = 1.0 * 5.0 + = 7.0 (v) + 1.0 * v(n2)(ac) 1.0 * 2.0 The AC voltage of node n4 is: v(n4)=v(n2)(op) * v(n1)(ac) + v(n1)(op) * v(n2)(ac) = 4.0 * 5.0 + 6.0 * 2.0 = 32.0 (v) Current-Dependent Current Sources — F-elements This section explains the F-element syntax and parameters. Note: G-elements with algebraics make F-elements obsolete. You can still use Felements for backward-compatibility with existing designs. Current-Controlled Current Source (CCCS) Syntax Linear Fxxx n+ n- <CCCS> vn1 gain <MAX=val> <MIN=val> <SCALE=val> 240 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Current-Dependent Current Sources — F-elements + <TC1=val> <TC2=val> <M=val> <ABS=1> <IC=val> Polynomial (POLY) Fxxx n+ n- <CCCS> POLY(ndim) vn1 <... vnndim> <MAX=val> + <MIN=val> <TC1=val> <TC2=val> <SCALE=val> <M=val> + <ABS=1> p0 <p1…> <IC=val> In this syntax, dim (dimensions) ≤3. Piecewise Linear (PWL) Fxxx n+ n- <CCCS> PWL(1) vn1 <DELTA=val> <SCALE=val> + <TC1=val> <TC2=val> <M=val> x1,y1 ... x100,y100 <IC=val> Multi-Input Gates Fxxx n+ n- <CCCS> gatetype(k) vn1, ... vnk <DELTA=val> + <SCALE=val> <TC1=val> <TC2=val> <M=val> <ABS=1> + x1,y1 ... x100,y100 <IC=val> In this syntax, gatetype(k) can be AND, NAND, OR, or NOR gates. Delay Element Note: G-elements with algebraics make F-elements obsolete. You can still use Felements for backward-compatibility with existing designs. Fxxx n+ n- <CCCS> DELAY vn1 TD=val <SCALE=val> + <TC1=val><TC2=val> NPDELAY=val F-element Parameters The F-element parameters are described in the following list. Parameter Description ABS Output is an absolute value, if ABS=1. CCCS Keyword for current-controlled current source. CCCS is a HSPICE reserved keyword; do not use it as a node name. HSPICE® User Guide: Simulation and Analysis B-2008.09 241 Chapter 9: Sources and Stimuli Current-Dependent Current Sources — F-elements Parameter Description DELAY Keyword for the delay element. Same as for a current-controlled current source, but has an associated propagation delay, TD. Adjusts the propagation delay in the macro model (subcircuit) process. DELAY is a reserved word; do not use it as a node name. DELTA Controls the curvature of piecewise linear corners. The default is 1/4 of the smallest distance between breakpoints. The maximum is 1/2 of the smallest distance between breakpoints. Fxxx Element name of the current-controlled current source. Must begin with F, followed by up to 1023 alphanumeric characters. gain Current gain. gatetype(k) AND, NAND, OR, or NOR. k is the number of inputs for the gate. x and y are the piecewise linear variation of the output, as a function of input. In multi-input gates, only one input determines the output state. Do not use the above keywords as node names. IC Initial condition (estimate) of the controlling current(s), in amps. If you do not specify IC, the default=0.0. M Number of replications of the element, in parallel. MAX Maximum output current. Default=undefined; sets no maximum. MIN Minimum output current. Default=undefined; sets no minimum. n+/- Connecting nodes for a positive or negative controlled source. NDIM Number of polynomial dimensions. If you do not specify POLY(NDIM), HSPICE or HSPICE RF assumes a one-dimensional polynomial. NDIM must be a positive number. NPDELAY Number of data points to use in delay simulations. The default value is the larger of either 10, or the smaller of TD/tstep and tstop/tstep. That min 〈 TD, tstop〉 is, NPDELAY default = max ------------------------------------------- , 10 The .TRAN tstep statement specifies the tstep and tstop values. 242 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Current-Dependent Current Sources — F-elements Parameter Description P0, P1 … The polynomial coefficients. If you specify one coefficient, HSPICE or HSPICE RF assumes it is P1 (P0=0.0), and the source element is linear. If you specify more than one polynomial coefficient, then the source is non-linear, and HSPICE or HSPICE RF assumes that the polynomials are P0, P1, P2 … See Polynomial Functions on page 216. POLY Keyword for the polynomial function. If you do not specify POLY(ndim), HSPICE assumes that this is a one-dimensional polynomial. Ndim must be a positive number. PWL Keyword for the piecewise linear function. SCALE Multiplier for the element value. TC1,TC2 First-order and second-order temperature coefficients. Temperature changes update the SCALE: SCALEeff = SCALE ⋅ ( 1 + TC 1 ⋅ Δ t + TC 2 ⋅ Δ t 2 ) TD Keyword for the time (propagation) delay. vn1 … Names of voltage sources, through which the controlling current flows. Specify one name for each dimension. x1,... Controlling current, through the vn1 source. Specify the x values in increasing order. y1,... Corresponding output current values of x. F-element Examples Example 1 This example describes a current-controlled current source, connected between nodes 13 and 5. The current, which controls the value of the controlled source, flows through the voltage source named VSENS. F1 13 5 VSENS MAX=+3 MIN=-3 5 Note: To use a current-controlled current source, you can place a dummy independent voltage source into the path of the controlling current. HSPICE® User Guide: Simulation and Analysis B-2008.09 243 Chapter 9: Sources and Stimuli Voltage-Dependent Current Sources — G-elements The defining equation is: I ( F 1 ) = 5 ⋅ I ( VSENS ) ■ Current gain is 5. ■ Maximum current flow through F1 is 3 A. ■ Minimum current flow is -3 A. If I(VSENS)=2 A, then this examples sets I(F1) to 3 amps, not 10 amps (as the equation suggests). You can define a parameter for the polynomial coefficient(s): .PARAM VU=5 F1 13 5 VSENS MAX=+3 MIN=-3 VU Example 2 This example is a current-controlled current source, with the value: I(F2)=1e-3 + 1.3e-3 ⋅ I(VCC) Current flows from the positive node, through the source, to the negative node. The positive controlling-current flows from the positive node, through the source, to the negative node of vnam (linear), or to the negative node of each voltage source (nonlinear). F2 12 10 POLY VCC 1MA 1.3M Example 3 This example is a delayed, current-controlled current source. Fd 1 0 DELAY vin TD=7ns SCALE=5 Example 4 This example is a piecewise-linear, current-controlled current source. Filim 0 out PWL(1) vsrc -1a,-1a 1a,1a Voltage-Dependent Current Sources — G-elements This section explains G-element syntax statements, and their parameters. Gxxx n+ n- <VCCS|LEVEL=0> in+ in- ... ■ ■ 244 LEVEL=0 is a Voltage-Controlled Current Source (VCCS). LEVEL=1 is a Voltage-Controlled Resistor (VCR). HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Voltage-Dependent Current Sources — G-elements ■ LEVEL=2 is a Voltage-Controlled Capacitor (VCCAP), Negative Piece-Wise Linear (NPWL). ■ LEVEL=3 is a VCCAP, Positive Piece-Wise Linear (PPWL). See also Using G- and E-elements. Voltage-Controlled Current Source (VCCS) Linear Gxxx n+ n- <VCCS> in+ in- transconductance <MAX=val> + <MIN=val> <SCALE=val> <M=val> <TC1=val> <TC2=val> + <ABS=1> <IC=val> For a description of the G-element parameters, see G-element Parameters on page 250. Polynomial (POLY) Gxxx n+ n- <VCCS> POLY(NDIM) in1+ in1- ... <inndim+ inndim-> + <MAX=val> <MIN=val> <SCALE=val> <M=val> <TC1=val> + <TC2=val> <ABS=1> P0<P1…> <IC=vals> For a description of the G-element parameters, see G-element Parameters on page 250. For a description of possible POLY syntaxes, see Polynomial Functions on page 216. Piecewise Linear (PWL) Gxxx n+ n- <VCCS> PWL(1) in+ in- <DELTA=val> + <SCALE=val> <M=val> <TC1=val> <TC2=val> + x1,y1 x2,y2 ... x100,y100 <IC=val> <SMOOTH=val> Gxxx n+ n- <VCCS> NPWL(1) in+ in- <DELTA=val> + <SCALE=val> <M=val> <TC1=val><TC2=val> + x1,y1 x2,y2 ... x100,y100 <IC=val> <SMOOTH=val> Gxxx n+ n- <VCCS> PPWL(1) in+ in- <DELTA=val> + <SCALE=val> <M=val> <TC1=val> <TC2=val> + x1,y1 x2,y2 ... x100,y100 <IC=val> <SMOOTH=val> For a description of the G-element parameters, see G-element Parameters on page 250. HSPICE® User Guide: Simulation and Analysis B-2008.09 245 Chapter 9: Sources and Stimuli Voltage-Dependent Current Sources — G-elements Multi-Input Gate Gxxx n+ n- <VCCS> gatetype(k) in1+ in1- ... + ink+ ink- <DELTA=val> <TC1=val> <TC2=val> <SCALE=val> + <M=val> x1,y1 ... x100,y100<IC=val> In this syntax, gatetype(k) can be AND, NAND, OR, or NOR gates. For a description of the G-element parameters, see G-element Parameters on page 250. Delay Element Gxxx n+ n- <VCCS> DELAY in+ in- TD=val <SCALE=val> + <TC1=val> <TC2=val> NPDELAY=val For a description of the G-element parameters, see G-element Parameters on page 250. Laplace Transform For details, see Laplace Transform on page 227. Pole-Zero Function For details, see Pole-Zero Function on page 228. Frequency Response Table For details, see Frequency Response Table on page 229. Foster Pole-Residue Form For details, see Foster Pole-Residue Form on page 230. Behavioral Current Source (Noise Model) Expression form gxxx node1 node2 noise=’noise_expression’ The xxx parameter can be set with a value up to 1024 characters. The node1 and node2 are the positive and negative nodes that connect to the noise source. The noise expression can contain the bias, frequency, or other parameters, and involve node voltages and currents through voltage sources. 246 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Voltage-Dependent Current Sources — G-elements For a description of the G-element parameters, see G-element Parameters on page 250. This syntax creates a simple two-terminal current noise source, whose value is described in A2/Hz. The output noise generated from this noise source is: noise_expression*H H is the transfer function from the terminal pair (node1,node2) to the circuit output, where the output noise is measured. You can also implement a behavioral noise source with an E-element. As noise elements, they are two-terminal elements that represent a noise source connected between two specified nodes. gname node1 node2 node3 node4 noise=’expression’ This syntax produces a noise source correlation between the terminal pairs (node1 node2) and (node3 node4). The resulting output noise is computed as: noise_expression*sqrt(H1*H2*) ■ H1 is the transfer function from (node1,node2) to the output. ■ H2 is the transfer function from (node3,node4) to the output. The noise expression can involve node voltages and currents through voltage sources. Data form Gxxx node1 node2 noise data=dataname .DATA dataname + pname1 pname2 + freq1 noise1 + freq2 noise2 + ... .enddata The data form defines a basic frequency-noise table. The .DATA statement contains two parameters: frequency and noise to specify the noise value at each frequency point. The unit for frequency is hertz, and the unit for noise is A2/Hz. For a description of the G-element parameters, see G-element Parameters on page 250. HSPICE® User Guide: Simulation and Analysis B-2008.09 247 Chapter 9: Sources and Stimuli Voltage-Dependent Current Sources — G-elements Example The following netlist shows a 1000 ohm resistor (g1) using a G-element. The g1noise element, placed in parallel with the g1 resistor, delivers the thermal noise expected from a resistor. The r1 resistor is included for comparison: The noise due to r1 should be the same as the noise due to g1noise. * Resistor implemented using g-element v1 1 0 1 r1 1 2 1k g1 1 2 cur='v(1,2)*0.001' g1noise 1 2 + noise='4*1.3806266e-23*(TEMPER+273.15)*0.001' rout 2 0 1meg .ac lin 1 100 100 .noise v(2) v1 1 .end Voltage-Controlled Resistor (VCR) Linear Gxxx n+ n- VCR in+ in- transfactor <MAX=val> <MIN=val> + <SCALE=val> <M=val> <TC1=val> <TC2=val> <IC=val> For a description of the G-element parameters, see G-element Parameters on page 250. Polynomial (POLY) Gxxx n+ n- VCR POLY(NDIM) in1+ in1- ... + <inndim+ inndim-> <MAX=val> <MIN=val><SCALE=val> + <M=val> <TC1=val> <TC2=val> P0 <P1…> <IC=vals> For a description of the G-element parameters, see G-element Parameters on page 250. Piecewise Linear (PWL) Gxxx n+ n- VCR PWL(1) in+ in- <DELTA=val> <SCALE=val> + <M=val> <TC1=val> <TC2=val> x1,y1 x2,y2 ... x100,y100 + <IC=val> <SMOOTH=val> Gxxx n+ n- VCR NPWL(1) in+ in- <DELTA=val> <SCALE=val> + <M=val> <TC1=val> <TC2=val> x1,y1 x2,y2 ... x100,y100 248 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Voltage-Dependent Current Sources — G-elements + <IC=val> <SMOOTH=val> Gxxx n+ n- VCR PPWL(1) in+ in- <DELTA=val> <SCALE=val> + <M=val> <TC1=val> <TC2=val> x1,y1 x2,y2 ... x100,y100 + <IC=val> <SMOOTH=val> For a description of the G-element parameters, see G-element Parameters on page 250. Multi-Input Gates Gxxx n+ n- VCR gatetype(k) in1+ in1- ... ink+ ink+ <DELTA=val> <TC1=val> <TC2=val> <SCALE=val> <M=val> + x1,y1 ... x100,y100 <IC=val> For a description of the G-element parameters, see G-element Parameters on page 250. Voltage-Controlled Capacitor (VCCAP) Gxxx n+ n- VCCAP PWL(1) in+ in<DELTA=val> + <SCALE=val> <M=val> <TC1=val> <TC2=val> + x1,y1 x2,y2 ... x100,y100 <IC=val> <SMOOTH=val> HSPICE or HSPICE RF uses either LEVEL=2 (NPWL) or LEVEL=3 (PPWL), based on the relationship of the (n+, n-) and (in+, in-) nodes. For a description of the G-element parameters, see G-element Parameters on page 250. Use the NPWL and PPWL functions to interchange the n+ and n- nodes, but use the same transfer function. The following summarizes this action: NPWL Function For the in- node connected to n+: ■ If v(n+,n-) < 0, then the controlling voltage is v(in+,in-). ■ Otherwise, the controlling voltage is v(in+,n-). For the in- node connected to n-: ■ If v(n+,n-) > 0, then the controlling voltage is v(in+,in-). ■ Otherwise, the controlling voltage is v(in+,n+). HSPICE® User Guide: Simulation and Analysis B-2008.09 249 Chapter 9: Sources and Stimuli Voltage-Dependent Current Sources — G-elements PPWL Function For the in- node, connected to n+: ■ If v(n+,n-) > 0, then the controlling voltage is v(in+,in-). ■ Otherwise, the controlling voltage is v(in+,n-). For the in- node, connected to n-: ■ If v(n+,n-) < 0, then the controlling voltage is v(in+,in-). ■ Otherwise, the controlling voltage is v(in+,n+). If the in- node does not connect to either n+ or n-, then HSPICE or HSPICE RF changes NPWL and PPWL to PWL. G-element Parameters The G-element parameters described in the following list. Parameter Description ABS Output is an absolute value, if ABS=1. CUR, VALUE, NOISE Current output that flows from n+ to n-. The expression that you define can be a function of: ■ ■ ■ ■ ■ node voltages branch currents time (time variable) temperature (temper variable) frequency (hertz variable) DELAY DELTA Controls curvature of piecewise linear corners. Defaults to 1/4 of the smallest distance between breakpoints. Maximum is 1/2 of the smallest distance between breakpoints. Gxxx 250 Keyword for the delay element. Same as in the voltage-controlled current source, but has an associated propagation delay, TD. Adjusts propagation delay in macro (subcircuit) modeling. DELAY is a keyword; do not use it as a node name. Name of the voltage-controlled element. Must begin with G, followed by up to 1023 alphanumeric characters. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Voltage-Dependent Current Sources — G-elements Parameter Description gatetype(k) AND, NAND, OR, or NOR. The k parameter is the number of inputs of the gate. x and y represent the piecewise linear variation of the output, as a function of the input. In multi-input gates, only one input determines the state of the output. LEVEL=<x> Function keyword such as VCCS, VCAP, etc. IC Initial condition. Initial estimate of the value(s) of controlling voltage(s). If you do not specify IC, the default=0.0. in +/- Positive or negative controlling nodes. Specify one pair for each dimension. M Number of replications of the elements in parallel. MAX Maximum value of the current or resistance. The default is undefined, and sets no maximum value. MIN Minimum value of the current or resistance. The default is undefined, and sets no minimum value. n+/- Positive or negative node of the controlled element. NDIM Number of polynomial dimensions. If you do not specify POLY(NDIM), HSPICE assumes a one-dimensional polynomial. NDIM must be a positive number. NPDELAY Sets the number of data points to use in delay simulations. The default value is the larger of either 10, or the smaller of TD/tstep and tstop/tstep. That is, min 〈 TD, tstop〉 NPDELAY default = max ------------------------------------------- , 10 . tstep The .TRAN statement specifies the tstep and tstop values. NPWL Models symmetrical bidirectional switch/transfer gate, NMOS. HSPICE® User Guide: Simulation and Analysis B-2008.09 251 Chapter 9: Sources and Stimuli Voltage-Dependent Current Sources — G-elements Parameter Description P0, P1 … The polynomial coefficients. ■ ■ If you specify one coefficient, HSPICE or HSPICE RF assumes that it is P1 (P0=0.0), and the element is linear. If you specify more than one polynomial coefficient, the element is non-linear, and the coefficients are P0, P1, P2 ... (see Polynomial Functions on page 216). POLY Keyword for the polynomial dimension function. If you do not specify POLY(ndim), HSPICE assumes that it is a one-dimensional polynomial. Ndim must be a positive number. PWL Keyword for the piecewise linear function. PPWL Models symmetrical bidirectional switch/transfer gate, PMOS. SCALE Multiplier for the element value. SMOOTH For piecewise-linear, dependent-source elements, SMOOTH selects the curve-smoothing method. A curve-smoothing method simulates exact data points that you provide. You can use this method to make HSPICE or HSPICE RF simulate specific data points, which correspond to either measured data or data sheets. Choices for SMOOTH are 1 or 2: ■ ■ TC1,TC2 Selects the smoothing method used in Hspice versions before release H93A. Use this method to maintain compatibility with simulations that you ran, using releases older than H93A. Selects the smoothing method, which uses data points that you provide. This is the default for Hspice versions starting with release H93A. First-order and second-order temperature coefficients. Temperature changes update the SCALE: SCALEeff = SCALE ⋅ ( 1 + TC 1 ⋅ Δ t + TC 2 ⋅ Δ t 2 ) . TD Keyword for the time (propagation) delay. transconductance Voltage-to-current conversion factor. transfactor 252 Voltage-to-resistance conversion factor. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Voltage-Dependent Current Sources — G-elements Parameter Description VCCAP Keyword for voltage-controlled capacitance element. VCCAP is a reserved HSPICE keyword; do not use it as a node name. VCCS Keyword for the voltage-controlled current source. VCCS is a reserved HSPICE keyword; do not use it as a node name. VCR Keyword for the voltage controlled resistor element. VCR is a reserved HSPICE keyword; do not use it as a node name. x1,... Controlling voltage, across the in+ and in- nodes. Specify the x values in increasing order. y1,... Corresponding element values of x. G-element Examples Modeling Switches You can model a switch to be open or closed based on simulation time or a pair of controlling nodes. Switch Example 1: Time-varying switch—use the built-in function TIME to change the value of R from 0 (closed) to 100g ohm (open) when the simulator reaches time value T1: R1 n1 n2 '100g*(TIME <= T1)' As long as TIME ≤ T1, the expression evaluates to zero and so does the resistor (switch) value. The resistor could easily be rewritten to switch from closed to open: R1 n1 n2 '100g*(TIME >= T1)' Switch example 2: Voltage-controlled switch—use a voltage-controlled resistor and the PWL (piece-wise linear) function. The point-value pair represents the controlling input and output resistance respectively G_Switch n1 n2 VCR PWL(1) c1 c2 0v,100g 1v,1p HSPICE® User Guide: Simulation and Analysis B-2008.09 253 Chapter 9: Sources and Stimuli Voltage-Dependent Current Sources — G-elements where: n1 and n2 are the poles of the switch, and c1 and c2 are the control nodes. In the following sample netlist, the switch is controlled by the PWL voltage source to switch at 1us: * g-element switch .option post V_ctrl c1 0 PWL (0 0v .99u .001v 1u 1v) G_Switch n1 n2 VCR PWL(1) c1 0 0v,100g 1v,1p V_ref n1 0 10v R_load n2 0 100 .tran .1u 2u .end Switch example 3—A voltage-controlled resistor represents a basic switch characteristic. The resistance between nodes 2 and 0 varies linearly from 10 meg to 1 m ohms, when voltage across nodes 1 and 0 varies between 0 and 1 volt. The resistance remains at 10 meg when below the lower voltage limit, and at 1 m ohms when above the upper voltage limit. Gswitch 2 0 VCR PWL(1) 1 0 0v,10meg 1v,1m Switch-Level MOSFET To model a switch level n-channel MOSFET, use the N-piecewise linear resistance switch. The resistance value does not change when you switch the d and s node positions. Gnmos d s VCR NPWL(1) g s LEVEL=1 0.4v,150g + 1v,10meg 2v,50k 3v,4k 5v,2k Runtime Current Source with Equation Containing Output Variable HSPICE does not support a runtime output variable such as v(gate) in the example equation that follows. If the .DATA block has a runtime current source (I-element) where an equation contains runtime output variable such as v(gate), as in this example equation, I0 1 0 '(1-a0*v(gate))/b0' vg gate 0 '(gt_vl)' \$ (gt_vl) —then the recommended method is to use the G-element: g0 1 0 cur='((1-(a0*v(gate)))/b0)' 254 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Voltage-Dependent Current Sources — G-elements Voltage-Controlled Capacitor The capacitance value across the (out,0) nodes varies linearly (from 1 p to 5 p), when voltage across the ctrl,0 nodes varies between 2 v and 2.5 v. The capacitance value remains constant at 1 picofarad when below the lower voltage limit, and at 5 picofarads when above the upper voltage limit. Gcap out 0 VCCAP PWL(1) ctrl 0 2v,1p 2.5v,5p Zero-Delay Gate To implement a two-input AND gate, use an expression and a piecewise linear table. ■ The inputs are voltages at the a and b nodes. ■ The output is the current flow from the out to 0 node. ■ HSPICE or HSPICE RF multiplies the current by the SCALE value—which in this example, is the inverse of the load resistance, connected across the out,0 nodes. Gand out 0 AND(2) a 0 b 0 SCALE=’1/rload’ 0v,0a 1v,.5a + 4v,4.5a 5v,5a Delay Element A delay is a low-pass filter type delay, similar to that of an opamp. In contrast, a transmission line has an infinite frequency response. A glitch input to a G delay attenuates in a way that is similar to a buffer circuit. In this example, the output of the delay element is the current flow from the out node to the 1 node with a value equal to the voltage across the (in, 0) nodes, multiplied by the SCALE value, and delayed by the TD value. Gdel out 0 DELAY in 0 TD=5ns SCALE=2 NPDELAY=25 Diode Equation To model forward-bias diode characteristics from node 5 to ground use a runtime expression. The saturation current is 1e-14 amp and the thermal voltage is 0.025 v. Gdio 5 0 CUR=’1e-14*(EXP(V(5)/0.025)-1.0)’ HSPICE® User Guide: Simulation and Analysis B-2008.09 255 Chapter 9: Sources and Stimuli Current-Dependent Voltage Sources — H-elements Diode Breakdown You can model the diode breakdown region to a forward region. When voltage across a diode is above or below the piecewise linear limit values (-2.2v, 2v), the diode current remains at the corresponding limit values (-1a, 1.2a). Gdiode 1 0 PWL(1) 1 0 -2.2v,-1a -2v,-1pa .3v,.15pa +.6v,10ua 1v,1a 2v,1.2a Triodes Both of the following voltage-controlled current sources implement a basic triode. ■ The first example uses the poly(2) operator, to multiply the anode and grid voltages together, and to scale by .02. ■ The second example uses the explicit behavioral algebraic description. gt i_anode cathode poly(2) anode,cathode + grid,cathode 0 0 0 0 .02 gt i_anode cathode + cur=’20m*v(anode,cathode)*v(grid,cathode)’ Behavioral Noise Model The following netlist shows a 1000 Ohm resistor (g1) implemented using a Gelement. The g1noise element, placed in parallel with the g1 resistor, delivers the thermal noise expected from a resistor. The r1 resistor is included for comparison: the noise due to r1 should be the same as the noise due to g1noise. * Resistor implemented using g-element v1 1 0 1 r1 1 2 1k g1 1 2 cur='v(1,2)*0.001' g1noise 1 2 noise='sqrt(4*1.3806266e-23*(TEMPER+273.15)*0.001)' rout 2 0 1meg .ac lin 1 100 100 .noise v(2) v1 1 .end Current-Dependent Voltage Sources — H-elements This section explains H-element syntax statements, and defines their parameters. 256 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Current-Dependent Voltage Sources — H-elements Note: E-elements with algebraics make H-elements obsolete. You can still use H-elements for backward-compatibility with existing designs. Current-Controlled Voltage Source (CCVS) Linear Hxxx n+ n- <CCVS> vn1 transresistance <MAX=val> <MIN=val> + <SCALE=val> <TC1=val><TC2=val> <ABS=1> <IC=val> Polynomial (POLY) Hxxx n+ n- <CCVS> POLY(NDIM) vn1 <... vnndim> + <MAX=val><MIN=val> <TC1=val> <TC2=val> <SCALE=val> + <ABS=1> P0 <P1…> <IC=val> Piecewise Linear (PWL) Hxxx n+ n- <CCVS> PWL(1) vn1 <DELTA=val> <SCALE=val> + <TC1=val> <TC2=val> x1,y1 ... x100,y100 <IC=val> Multi-Input Gate Hxxx n+ n- gatetype(k) vn1, ...vnk <DELTA=val> <SCALE=val> + <TC1=val> <TC2=val> x1,y1 ... x100,y100 <IC=val> In this syntax, gatetype(k) can be AND, NAND, OR, or NOR gates. Delay Element Note: E-elements with algebraics make CCVS elements obsolete. You can still use CCVS elements for backward-compatibility with existing designs. Hxxx n+ n- <CCVS> DELAY vn1 TD=val <SCALE=val> <TC1=val> + <TC2=val> <NPDELAY=val> HSPICE® User Guide: Simulation and Analysis B-2008.09 257 Chapter 9: Sources and Stimuli Current-Dependent Voltage Sources — H-elements Parameter ABS Output is an absolute value, if ABS=1. CCVS Keyword for the current-controlled voltage source. CCVS is a HSPICE reserved keyword; do not use it as a node name. DELAY Keyword for the delay element. Same as for a current-controlled voltage source, but has an associated propagation delay, TD. Use this element to adjust the propagation delay in the macro (subcircuit) model process. DELAY is a HSPICE reserved keyword; do not use it as a node name. DELTA Controls curvature of piecewise linear corners. The default is 1/4 of the smallest distance between breakpoints. Maximum is 1/2 of the smallest distance between breakpoints. gatetype(k) Can be AND, NAND, OR, or NOR. The k value is the number of inputs of the gate. The x and y terms are the piecewise linear variation of the output, as a function of the input. In multi-input gates, one input determines the output state. Hxxx Element name of current-controlled voltage source. Must start with H, followed by up to 1023 alphanumeric characters. IC Initial condition (estimate) of the controlling current(s), in amps. If you do not specify IC, the default=0.0. MAX Maximum voltage. Default is undefined; sets no maximum. MIN Minimum voltage. Default is undefined; sets no minimum. n+/- Connecting nodes for positive or negative controlled source. NDIM 258 Description Number of polynomial dimensions. If you do not specify POLY(NDIM), HSPICE or HSPICE RF assumes a one-dimensional polynomial. NDIM must be a positive number. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Current-Dependent Voltage Sources — H-elements Parameter Description NPDELAY Number of data points to use in delay simulations. The default value is the larger of either 10, or the smaller of TD/tstep and tstop/tstep. min 〈 TD, tstop〉 tstep That is: NPDELAY default = max ------------------------------------------- , 10 . The .TRAN statement specifies the tstep and tstop values. P0, P1 . . . Polynomial coefficients. ■ ■ If you specify one polynomial coefficient, the source is linear, and HSPICE or HSPICE RF assumes that the polynomial is P1 (P0=0.0). If you specify more than one polynomial coefficient, the source is non-linear. HSPICE assumes the polynomials are P0, P1, P2 … See Polynomial Functions on page 216. POLY Keyword for polynomial dimension function. If you do not specify POLY(ndim), HSPICE assumes a one-dimensional polynomial. Ndim must be a positive number. PWL Keyword for a piecewise linear function. SCALE Multiplier for the element value. TC1,TC2 First-order and second-order temperature coefficients. Temperature changes update the SCALE: SCALEeff = SCALE ⋅ ( 1 + TC 1 ⋅ Δ t + TC 2 ⋅ Δ t 2 ) TD Keyword for the time (propagation) delay. transresistance Current-to-voltage conversion factor. vn1 … Names of voltage sources, through which controlling current flows. You must specify one name for each dimension. x1,... Controlling current, through the vn1 source. Specify the x values in increasing order. y1,... Corresponding output voltage values of x. Example 1 HX 20 10 VCUR MAX=+10 MIN=-10 1000 HSPICE® User Guide: Simulation and Analysis B-2008.09 259 Chapter 9: Sources and Stimuli Current-Dependent Voltage Sources — H-elements The example above selects a linear current-controlled voltage source. The controlling current flows through the dependent voltage source, called VCUR. Example 2 The defining equation of the CCVS is: H X = 1000 ⋅ I ( VCUR ) The defining equation specifies that the voltage output of HX is 1000 times the value of the current flowing through VCUR. ■ If the equation produces a value of HX greater than +10 V, then the MAX parameter sets HX to 10 V. ■ If the equation produces a value of HX less than -10 V, then the MIN parameter sets HX to -10 V. VCUR is the name of the independent voltage source, through which the controlling current flows. If the controlling current does not flow through an independent voltage source, you must insert a dummy independent voltage source. Example 3 .PARAM CT=1000 HX 20 10 VCUR MAX=+10 MIN=-10 CT HXY 13 20 POLY(2) VIN1 VIN2 0 0 0 0 1 IC=0.5, 1.3 The example above describes a dependent voltage source, with the value: V = I ( VIN 1 ) ⋅ I ( VIN 2 ) This two-dimensional polynomial equation specifies: ■ FA1=VIN1 ■ FA2=VIN2 ■ P0=0 ■ P1=0 ■ P2=0 ■ P3=0 ■ P4=1 The initial controlling current is .5 mA through VIN1, and 1.3 mA for VIN2. 260 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Specifying a Digital Vector File and Mixed Mode Stimuli Positive controlling current flows from the positive node, through the source, to the negative node of vnam (linear). The (non-linear) polynomial specifies the source voltage, as a function of the controlling current(s). Specifying a Digital Vector File and Mixed Mode Stimuli HSPICE and HSPICE RF input netlists support digital vector files. A VEC file consists of three parts: ■ Vector Pattern Definition section ■ Waveform Characteristics section ■ Tabular Data section To incorporate this information into your simulation, include the .VEC command in your netlist. Commands in a Digital Vector File For descriptions of all commands that you can use in a VEC file, see Digital Vector File Commands in the HSPICE Reference Manual: Commands and Control Options. Vector Patterns The Vector Pattern Definition section defines the vectors, their names, sizes, signal direction, sequence or order for each vector stimulus, and so on. A RADIX line must occur first and the other lines can appear in any order in this section. All keywords are case-insensitive. Here is an example Vector Pattern Definition section: ; start of Vector Pattern Definition section RADIX 1111 1111 VNAME A B C D E F G H IO IIII IIII TUNIT ns These four lines are required and appear in the first lines of a VEC file: ■ RADIX defines eight single-bit vectors. ■ VNAME gives each vector a name. HSPICE® User Guide: Simulation and Analysis B-2008.09 261 Chapter 9: Sources and Stimuli Specifying a Digital Vector File and Mixed Mode Stimuli ■ IO determines which vectors are inputs, outputs, or bidirectional signals. In this example, all eight are input signals. ■ TUNIT indicates that the time unit for the tabular data to follow is in units of nanoseconds. For additional information about these keywords, see Defining Tabular Data on page 262. Defining Tabular Data Although the Tabular Data section generally appears last in a VEC file (after the Vector Pattern and Waveform Characteristics definitions), this chapter describes it first to introduce the definitions of a vector. The Tabular Data section defines (in tabular format) the values of the signals at specified times. Rows in the Tabular Data section must appear in chronological order because row placement carries sequential timing information. Its general format is: time1 signal1_value1 signal2_value1 signal3_value1... time2 signal1_value2 signal2_value2 signal3_value2... time3 signal1_value3 signal2_value3 signal3_value3... . . Where timex is the specified time, and signaln_valuen is the values of specific signals at specific points in time. The set of values for a particular signal (over all times) is a vector, which appears as a vertical column in the tabular data and vector table. The set of all signal1_valuen constitutes one vector. For example, 11.0 1000 1000 20.0 1100 1100 33.0 1010 1001 This example shows that: ■ ■ At 20.0 time units, the first, second, fifth, and sixth vectors are 1. ■ 262 At 11.0 time units, the value for the first and fifth vectors is 1. At 33.0 time units, the first, third, fifth, and eighth vectors are 1. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Specifying a Digital Vector File and Mixed Mode Stimuli Input Stimuli HSPICE or HSPICE RF converts each input signal into a PWL (piecewise linear) voltage source, and a series resistance. Table 15 shows the legal states for an input signal. Signal values can have any of these legal states. Table 15 Legal States for an Input Signal State Description 0 Drive to ZERO (gnd). Resistance set to 0. 1 Drive to ONE (vdd). Resistance set to 0. Z, z Floating to HIGH IMPEDANCE. A TRIZ statement defines resistance value. X, x Drive to ZERO (gnd). Resistance set to 0. L Resistive drive to ZERO (gnd). An OUT or OUTZ statement defines resistance value. H Resistive drive to ONE (vdd). An OUT or OUTZ statement defines resistance value. U, u Drive to ZERO (gnd). Resistance set to 0. Expected Output HSPICE or HSPICE RF converts each output signal into a .DOUT statement in the netlist. During simulation, HSPICE or HSPICE RF compares the actual results with the expected output vector(s). If the states are different, an error message appears. The legal states for expected outputs include the values listed in Table 16. Table 16 Legal States for an Output Signal State Description 0 Expect ZERO. 1 Expect ONE. X, x Don’t care. HSPICE® User Guide: Simulation and Analysis B-2008.09 263 Chapter 9: Sources and Stimuli Specifying a Digital Vector File and Mixed Mode Stimuli Table 16 Legal States for an Output Signal U, u Don’t care. Z, z Expect HIGH IMPEDANCE (don’t care). Simulation evaluates Z, z as “don’t care” because HSPICE or HSPICE RF cannot detect a high impedance state. For example, ... IO OOOO ; start of tabular section data 11.0 1001 20.0 1100 30.0 1000 35.0 xx00 Where, ■ The first line is a comment line because of the semicolon character. ■ The second line expects the output to be 1 for the first and fourth vectors, while all others are expected to be low. ■ At 20 time units, HSPICE or HSPICE RF expects the first and second vectors to be high, and the third and fourth to be low. ■ At 30 time units, HSPICE or HSPICE RF expects only the first vector to be high, and all others low. ■ At 35 time units, HSPICE or HSPICE RF expects the output of the first two vectors to be “don’t care”; it expects vectors 3 and 4 to be low. Verilog Value Format HSPICE or HSPICE RF accepts Verilog-sized format to specify numbers; for example, <size> ’<base format> <number> Where: ■ <size> specifies the number of bits, in decimal format. ■ <base format> indicates: • 264 binary (’b or ’B) HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Specifying a Digital Vector File and Mixed Mode Stimuli • • ■ octal (’o or ’O) hexadecimal (’h or ’H). <number> values are combinations of the 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, and F characters. Depending on what base format you choose, only a subset of these characters might be legal. You can also use unknown values (X) and high-impedance (Z) in the <number> field. An X or Z sets four bits in the hexadecimal base, three bits in the octal base, or one bit in the binary base. If the most significant bit of a number is 0, X, or Z, HSPICE or HSPICE RF automatically extends the number (if necessary), to fill the remaining bits with 0, X, or Z, respectively. If the most significant bit is 1, HSPICE or HSPICE RF uses 0 to extend it. For example, 4’b1111 12’hABx 32’bZ 8’h1 This example specifies values for: • 4-bit signal in binary • 12-bit signal in hexadecimal • 32-bit signal in binary • 8-bit signal in hexadecimal Equivalents of these lines in non-Verilog format, are: 1111 AB xxxx ZZZZ ZZZZ ZZZZ ZZZZ ZZZZ ZZZZ ZZZZ ZZZZ 0000 0001 Periodic Tabular Data Tabular data is often periodic, so you do not need to specify the absolute time at every time point. When you specify the PERIOD statement, the Tabular Data section omits the absolute times. For more information, see Defining Tabular Data on page 262. HSPICE® User Guide: Simulation and Analysis B-2008.09 265 Chapter 9: Sources and Stimuli Specifying a Digital Vector File and Mixed Mode Stimuli For example, the PERIOD statement in the following sets the time interval to 10ns between successive lines in the tabular data. This is a shortcut when you use vectors in regular intervals throughout the entire simulation. RADIX 1111 1111 VNAME A B C D E F G H IO IIII IIII TUNIT ns PERIOD 10 ; start of vector data section 1000 1000 1100 1100 1010 1001 Waveform Characteristics The Waveform Characteristics section defines various attributes for signals, such as the rise or fall time, the thresholds for logic high or low, and so on. For example, TRISE 0.3 137F 0000 TFALL 0.5 137F 0000 VIH 5.0 137F 0000 VIL 0.0 137F 0000 The waveform characteristics are based on a bit-mask. Where: ■ The TRISE (signal rise time) setting of 0.3ns applies to the first four vectors, but not to the last four. ■ The example does not show how many bits are in each of the first four vectors, although the first vector is at least one bit. ■ The fourth vector is four bits because F is hexadecimal for binary 1111. ■ All bits of the fourth vector have a rise time of 0.3ns for the constant you defined in TUNIT. This also applies to TFALL (fall time), VIH (voltage for logic-high inputs), and VIL (voltage for logic-low inputs). Modifying Waveform Characteristics The TDELAY, IDELAY, and ODELAY statements define the delay time of the signal, relative to the absolute time of each row in the Tabular Data section. 266 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Specifying a Digital Vector File and Mixed Mode Stimuli ■ TDELAY applies to the input and output delay time of input, output, and bidirectional signals. ■ IDELAY applies to the input delay time of bidirectional signals. ■ ODELAY applies to the output delay time of bidirectional signals. The SLOPE statement specifies the rise and fall times for the input signal. To specify the signals to which the slope applies, use a mask. The TFALL statement sets an input fall time for specific vectors. The TRISE statement sets an input rise time for specific vectors. The TUNIT statement defines the time unit. The OUT and OUTZ keywords are equivalent, and specify output resistance for each signal (for which the mask applies); OUT (or OUTZ) applies only to input signals. The TRIZ statement specifies the output impedance, when the signal (for which the mask applies) is in tristate; TRIZ applies only to the input signals. The VIH statement specifies the logic-high voltage for each input signal to which the mask applies. The VIL statement specifies the logic-low voltage for each input signal to which the mask applies. Similar to the TDELAY statement, the VREF statement specifies the name of the reference voltage for each input vector to which the mask applies. VREF applies only to input signals. Similar to the TDELAY statement, the VTH statement specifies the logic threshold voltage for each output signal to which the mask applies. The threshold voltage determines the logic state of output signals for comparison with the expected output signals. The VOH statement specifies the logic-high voltage for each output signal to which the mask applies. The VOL statement specifies the logic-low voltage for each output signal to which the mask applies. Using the Context-Based Control Option The OPTION CBC (Context-Based Control) specifies the direction of bidirectional signals. A bidirectional signal is an input if its value is 0, 1, or Z; conversely, a bidirectional signal is an output if its value is H, L, U, or X. HSPICE® User Guide: Simulation and Analysis B-2008.09 267 Chapter 9: Sources and Stimuli Specifying a Digital Vector File and Mixed Mode Stimuli For example, RADIX 1 1 1 IO I O B VNAME A Z B OPTION CBC 10.0 0 X L 20.0 1 1 H 30.0 1 0 Z This example sets up three vectors, named A, Z, and B. Vector A is an input, vector Z is an output, and vector B is a bidirectional signal (defined in the IO statement). The OPTION CBC line turns on context-based control. The next line sets vector A to a logic-low at 10.0 ns, and vector Z is care.”do not care.” Because the L value is under vector B, HSPICE expects a logic-low output. At 20 ns, vector A transitions high, and the expected outputs at vectors Z and B are high. Finally, at 30 ns, HSPICE expects vector Z to be low, vector B changes from an output to a high-impedance input, and vector the A signal does not change. Comment Lines and Line Continuations Any line in a VEC file that begins with a semicolon (;) is a comment line. Comments can also start at any point along a line. HSPICE or HSPICE RF ignores characters after a semicolon. For example, ; This is a comment line radix 1 1 4 1234 ; This is a radix line As in netlists, any line in a VEC file that starts with a plus sign (+) is a continuation from the previous line. Parameter Usage You can use .PARAM statements with some VEC statements when you run HSPICE. These VEC statements fall into the three groups, which are described in the following sections. No other VEC statements but those identified here support .PARAM statements. 268 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Specifying a Digital Vector File and Mixed Mode Stimuli First Group ■ PERIOD ■ TDELAY ■ IDELAY ■ ODELAY ■ SLOPE ■ TRISE ■ TFALL For these statements, the TUNIT statement defines the time unit. If you do not include a TUNIT statement, the default time unit value is ns. Do not specify absolute unit values in a .PARAM statement. For example, if in your netlist: .param myperiod=10ns \$ ‘ns’ makes this incorrect And in your VEC file: tunit ns period myperiod What you wanted for the time period is 10ns; however, because you specified absolute units, 1e-8ns is the value used. In this example, the correct form is: .param myperiod=10 Second Group ■ OUT or OUTZ ■ TRIZ In these statements, the unit is ohms. ■ If you do not include an OUT (or OUTZ) statement, the default is 0. ■ If you do not include a TRIZ statement, the default is 1000M. The .PARAM definition for this group follows the HSPICE syntax. For example, if in your netlist: .param myout=10 \$ means 10 ohm .param mytriz= 10Meg \$ means 10,000,000 ohm, don't \$ confuse Meg with M, M means 0.001 HSPICE® User Guide: Simulation and Analysis B-2008.09 269 Chapter 9: Sources and Stimuli Specifying a Digital Vector File and Mixed Mode Stimuli And in your VEC file: out myout triz mytriz Then, HSPICE returns 10 ohm for OUT and 10,000,000 ohm for TRIZ. Third Group ■ VIH ■ VIL ■ VOH ■ VOL ■ VTH In these statements, the unit is volts. ■ ■ If you do not include a VIL statement, the default is 0.0. ■ If you do not include a VOH statement, the default is 2.64. ■ If you do not include an VOL statement, the default is 0.66. ■ 270 If you do not include an VIH statement, the default is 3.3. If you do not include an VTH statement, the default is 1.65. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 9: Sources and Stimuli Specifying a Digital Vector File and Mixed Mode Stimuli Digital Vector File Example ; specifies # of bits associated with each vector radix 1 2 444 ;******************************************************** ; defines name for each vector. For multi-bit vectors, ; innermost provide the bit index range, MSB:LSB vname v1 va[[1:0]] vb[12:1] ;actual signal names: v1, va[0], va[1], vb1, vb2, ... vb12 ;******************************************************** ; defines vector as input, output, or bi-directional io i o bbb ; defines time unit tunit ns ;******************************************************** ; vb12-vb5 are output when ‘v1’ is ‘high’ enable v1 0 0 FF0 ; vb4-vb1 are output when ‘v1’ is ‘low’ enable ~v1 0 0 00F ;******************************************************** ; all signals have a delay of 1 ns ; Note: do not put the unit (such as ns) here again. ; HSPICE multiplies this value by the specified ‘tunit’. tdelay 1.0 ; va1 and va0 signals have 1.5ns delays tdelay 1.5 0 3 000 ;******************************************************** ; specify input rise/fall times (if you want different ; rise/fall times, use the trise/tfall statement.) ; Note: do not put the unit (such as ns) here again. ; HSPICE multiplies this value by the specified ‘tunit’. slope 1.2 ;******************************************************** ; specify the logic ‘high’ voltage for input signals vih 3.3 1 0 000 vih 5.0 0 0 FFF ; to specify logic low, use ‘vil’ ;******************************************************** ; va & vb switch from ‘lo’ to ‘hi’ at 1.75 volts vth 1.75 0 1 FFF ;**************************************************** ; tabular data section 10.0 1 3 FFF 20.0 0 2 AFF 30.0 1 0 888 HSPICE® User Guide: Simulation and Analysis B-2008.09 271 Chapter 9: Sources and Stimuli Specifying a Digital Vector File and Mixed Mode Stimuli 272 HSPICE® User Guide: Simulation and Analysis B-2008.09 10 10 Parameters and Functions Describes how to use parameters within HSPICE and HSPICE RF netlists. Parameters are similar to the variables used in most programming languages. Parameters hold a value that you assign when you create your circuit design or that the simulation calculates based on circuit solution values. Parameters can store static values for a variety of quantities (resistance, source voltage, rise time, and so on). You can also use them in sweep or statistical analysis. For descriptions of individual commands referenced in this chapter, see Chapter 2, HSPICE and HSPICE RF Netlist Commands in the HSPICE Reference Manual: Commands and Control Options. These topics are covered in the following sections: ■ Using Parameters in Simulation (.PARAM) ■ Using Algebraic Expressions ■ Built-In Functions and Variables ■ Parameter Scoping and Passing Using Parameters in Simulation (.PARAM) Defining Parameters Parameters in HSPICE are names that you associate with numeric values. (See Assigning Parameters on page 275.) You can use any of the methods described in Table 17 to define parameters. HSPICE® User Guide: Simulation and Analysis B-2008.09 273 Chapter 10: Parameters and Functions Using Parameters in Simulation (.PARAM) Table 17 .PARAM Statement Syntax Parameter Description Simple assignment .PARAM <SimpleParam>=1e-12 Algebraic definition .PARAM <AlgebraicParam>=‘SimpleParam*8.2’ SimpleParam excludes the output variable. You can also use algebraic parameters in .PRINT and .PROBE statements. For example: .PRINT AlgebraicParam=par(’algebraic expression’) You can use the same syntax for .PROBE statements. See Using Algebraic Expressions on page 278. User-defined function .PARAM <MyFunc( x, y )>=‘Sqrt((x*x)+(y*y))’ Character string definition .PARAM <paramname>=str(‘string’) Subcircuit default .SUBCKT <SubName> <ParamDefName>=<Value> str(‘string’) .MACRO <SubName> <ParamDefName>=<Value> str(‘string’) Predefined analysis function .PARAM <mcVar>=Agauss(1.0,0.1) .MEASURE statement .MEASURE <DC | AC | TRAN> result TRIG ... + TARG ... <GOAL=val> <MINVAL=val> + <WEIGHT=val> <MeasType> <MeasParam> (See Specifying User-Defined Analysis (.MEASURE) on page 317.) .PRINT | .PROBE .PRINT | .PROBE + outParam=Par_Expression A parameter definition in HSPICE always uses the last value found in the input netlist (subject to local versus global parameter rules). These definitions assign a value of 3 to the DupParam parameter. .PARAM DupParam=1 ... .PARAM DupParam=3 274 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 10: Parameters and Functions Using Parameters in Simulation (.PARAM) HSPICE assigns 3 as the value for all instances of DupParam, including instances that are earlier in the input than the .PARAM DupParam=3 statement. All parameter values in HSPICE are IEEE double floating point numbers. The parameter resolution order is: 1. Resolve all literal assignments. 2. Resolve all expressions. 3. Resolve all function calls. Table 18 shows the parameter passing order. Table 18 Parameter Passing Order .OPTION PARHIER=GLOBAL .OPTION PARHIER=LOCAL Analysis sweep parameters Analysis sweep parameters .PARAM statement (library) .SUBCKT call (instance) .SUBCKT call (instance) .SUBCKT definition (symbol) .SUBCKT definition (symbol) .PARAM statement (library) Assigning Parameters You can assign the following types of values to parameters: ■ Constant real number ■ Algebraic expression of real values ■ Predefined function ■ Function that you define ■ Circuit value ■ Model value To invoke the algebraic processor, enclose a complex expression in single quotes. A simple expression consists of one parameter name. The parameter keeps the assigned value, unless: HSPICE® User Guide: Simulation and Analysis B-2008.09 275 ■ A later definition changes its value, or ■ An algebraic expression assigns a new value during simulation. HSPICE does not warn you, if it reassigns a parameter. Example: Modeling an eFuse You can model an electrically programmable eFUSE device as follows. Instantiate an eFUSE as a subcircuit and pass a parameter that determines whether the eFUSE is “blown” or intact: .subckt efuse in out blown=0 Rfuse in out r='2*(1-blown)+100e6*blown' .ends efuse If blown=0, then the fuse is intact (2 ohms). If blown=1 then the fuse is blown and you get the much higher resistance of 100 meg. To use the eFUSE, instantiate it with a subcircuit call: xefuse1 in out efuse blown=0 Alternately, you can control the eFUSE with a parameter setting: .param blown=1 x1 in out efuse Inline Parameter Assignments To define circuit values, use a direct algebraic evaluation: r1 n1 0 R=’1k/sqrt(HERTZ)’ \$ Resistance for frequency Parameters in Output To use an algebraic expression as an output variable in a .PRINT, .PROBE or .MEASURE statement, use the PAR keyword. (See Chapter 11, Simulation Output, for more information.) Example .PRINT DC v(3) gain=PAR(‘v(3)/v(2)’) PAR(‘v(4)/v(2)’) User-Defined Function Parameters You can define a function that is similar to the parameter assignment, but you cannot nest the functions more than two deep. HSPICE® User Guide: Simulation and Analysis B-2008.09 276 ■ An expression can contain parameters that you did not define. ■ A function must have at least one argument, and can have up to 20 (and in many cases, more than 20) arguments. ■ You can redefine functions. The format of a function is: funcname1(arg1[,arg2...])=expression1 + [funcname2(arg1[,arg2...])=expression2] off Parameter Description funcname Specifies the function name. This parameter must be distinct from array names and built-in functions. In subsequently defined functions, all embedded functions must be previously defined. arg1, arg2 Specifies variables used in the expression. off Voids all user-defined functions. Example .PARAM f(a,b)=POW(a,2)+a*b g(d)=SQRT(d) + h(e)=e*f(1,2)-g(3) Predefined Analysis Function HSPICE includes specialized analysis types, such as Optimization and Monte Carlo, that require a way to control the analysis. Measurement Parameters .MEASURE statements produce a measurement parameter. The rules for measurement parameters are the same as for standard parameters, except that measurement parameters are defined in a .MEASURE statement, not in a .PARAM statement. For a description of the .MEASURE statement, see Specifying User-Defined Analysis (.MEASURE) on page 317. HSPICE® User Guide: Simulation and Analysis B-2008.09 277 .PRINT and .PROBE Parameters .PRINT,and.PROBE statements in HSPICE produce a print parameter. The rules for print parameters are the same as the rules for standard parameters, except that you define the parameter directly in a.PRINT or.PROBE statement, not in a .PARAM statement For more information about the.PRINT or .PROBE statements, see Displaying Simulation Results on page 296. Multiply Parameter The most basic subcircuit parameter in HSPICE is the M (multiply) parameter. For a description of this parameter, see M (Multiply) Parameter on page 74. Using Algebraic Expressions Note: Synopsys HSPICE uses double-precision numbers (15 digits) for expressions, user-defined parameters, and sweep variables. For better precision, use parameters (instead of constants) in algebraic expressions because constants are only single-precision numbers (7 digits). In HSPICE, an algebraic expression, with quoted strings, can replace any parameter in the netlist. In HSPICE, you can then use these expressions as output variables in .PRINT, statements. Algebraic expressions can expand your options in an input netlist file. Some uses of algebraic expressions are: ■ Parameters: .PARAM x=’y+3’ ■ Functions: .PARAM rho(leff,weff)=’2+*leff*weff-2u’ ■ Algebra in elements: R1 1 0 r=’ABS(v(1)/i(m1))+10’ HSPICE® User Guide: Simulation and Analysis B-2008.09 278 ■ Algebra in .MEASURE statements: .MEAS vmax MAX V(1) .MEAS imax MAX I(q2) .MEAS ivmax PARAM=’vmax*imax’ ■ Algebra in output statements: .PRINT conductance=PAR(‘i(m1)/v(22)’) The basic syntax for using algebraic expressions for output is: PAR(‘algebraic expression’) In addition to using quotations, you must define the expression inside the PAR( ) statement for output.The continuation character for quoted parameter strings, in HSPICE, is a double backslash (\\). (Outside of quoted strings, the single backslash (\) is the continuation character.) Built-In Functions and Variables In addition to simple arithmetic operations (+, -, *, /), use the built-in functions listed in Table 19 and the variables listed in Table 18 on page 275 in HSPICE expressions. Table 19 Synopsys HSPICE Built-in Functions HSPICE Form Function Class Description sin(x) sine trig Returns the sine of x (radians) cos(x) cosine trig Returns the cosine of x (radians) tan(x) tangent trig Returns the tangent of x (radians) asin(x) arc sine trig Returns the inverse sine of x (radians) acos(x) arc cosine trig Returns the inverse cosine of x (radians) atan(x) arc tangent trig Returns the inverse tangent of x (radians) sinh(x) hyperbolic sine trig Returns the hyperbolic sine of x (radians) cosh(x) hyperbolic cosine trig Returns the hyperbolic cosine of x (radians) HSPICE® User Guide: Simulation and Analysis B-2008.09 279 Table 19 Synopsys HSPICE Built-in Functions (Continued) HSPICE Form Function Class Description tanh(x) hyperbolic tangent trig Returns the hyperbolic tangent of x (radians) abs(x) absolute value math Returns the absolute value of x: |x| sqrt(x) square root math Returns the square root of the absolute value of x: sqrt(-x)=-sqrt(|x|) pow(x,y) absolute power math Returns the value of x raised to the integer part of y: x(integer part of y) pwr(x,y) signed power math Returns the absolute value of x, raised to the y power, with the sign of x: (sign of x)|x|y x**y power If x<0, returns the value of x raised to the integer part of y. If x=0, returns 0. If x>0, returns the value of x raised to the y power. log(x) natural logarithm math Returns the natural logarithm of the absolute value of x, with the sign of x: (sign of x)log(|x|) log10(x) base 10 logarithm math Returns the base 10 logarithm of the absolute value of x, with the sign of x: (sign of x)log10(|x|) exp(x) exponential math Returns e, raised to the power x: ex db(x) decibels math Returns the base 10 logarithm of the absolute value of x, multiplied by 20, with the sign of x: (sign of x)20log10(|x|) int(x) integer math Returns the integer portion of x. The fractional portion of the number is lost. nint(x) integer math Rounds x up or down, to the nearest integer. HSPICE® User Guide: Simulation and Analysis B-2008.09 280 Table 19 Synopsys HSPICE Built-in Functions (Continued) HSPICE Form Function Class Description sgn(x) return sign math Returns -1 if x is less than 0. Returns 0 if x is equal to 0. Returns 1 if x is greater than 0 sign(x,y) transfer sign math Returns the absolute value of x, with the sign of y: (sign of y)|x| def(x) parameter defined control Returns 1 if parameter x is defined. min(x,y) smaller of two args control Returns the numeric minimum of x and y max(x,y) larger of two control args Returns the numeric maximum of x and y val(element) get value various Returns a parameter value for a specified element. For example, val(r1) returns the resistance value of the r1 resistor. val(element. parameter) get value various Returns a value for a specified parameter of a specified element. For example, val(rload.temp) returns the value of the temp (temperature) parameter for the rload element. val(model_type: model_name. model_param) get value various Returns a value for a specified parameter of a specified model of a specific type. For example, val(nmos:mos1.rs) returns the value of the rs parameter for the mos1 model, which is an nmos model type. Not supported for CMI models (Level 54 and greater). lv(<Element>) or lx(<Element>) element templates various Returns various element values during simulation. See Element Template Output (HSPICE Only) on page 316 for more information. v(<Node>), i(<Element>)... circuit output variables various Returns various circuit values during simulation. See DC and Transient Output Variables on page 301 for more information. Returns 0 if parameter x is not defined. HSPICE® User Guide: Simulation and Analysis B-2008.09 281 Table 19 Synopsys HSPICE Built-in Functions (Continued) HSPICE Form Function <cond> ?x : y ternary operator Returns x if cond is not zero. Otherwise, returns y. relational operator (less than) Returns 1 if the left operand is less than the right operand. Otherwise, returns 0. relational operator (less than or equal) Returns 1 if the left operand is less than or equal to the right operand. Otherwise, returns 0. relational operator (greater than) Returns 1 if the left operand is greater than the right operand. Otherwise, returns 0. relational operator (greater than or equal) Returns 1 if the left operand is greater than or equal to the right operand. Otherwise, returns 0. equality Returns 1 if the operands are equal. Otherwise, returns 0. < <= > >= == Class Description .param z= ‘condition ? x:y’ .para x=y<z (y less than z) .para x=y<=z (y less than or equal to z) .para x=y>z (y greater than z) .para x=y>=z (y greater than or equal to z) .para x=y==z (y equal to z) != inequality Returns 1 if the operands are not equal. Otherwise, returns 0. .para x=y!=z (y not equal to z) && Logical AND Returns 1 if neither operand is zero. Otherwise, returns 0. .para x=y&&z (y AND z) || Logical OR Returns 1 if either or both operands are not zero. Returns 0 only if both operands are zero. .para x=y||z (y OR z) HSPICE® User Guide: Simulation and Analysis B-2008.09 282 Example .parameters p1=4 p2=5 p3=6 r1 1 0 value='p1 ? p2+1 : p3' HSPICE reserves the variable names listed in Table 20 on page 283 for use in elements, such as E, G, R, C, and L. You can use them in expressions, but you cannot redefine them; for example, this statement would be illegal: .param temper=100 Table 20 Synopsys HSPICE Special Variables HSPICE Form Function Class Description time current simulation time control Uses parameters to define the current simulation time, during transient analysis. temper current circuit temperature control Uses parameters to define the current simulation temperature, during transient/temperature analysis. You can use the HSPICE simulation temperature in an equation by using the temper variable parameter. For example: .temp 20 50 100 .par x="temper/2" v0 1 0 1 r0 1 0 r=x hertz current simulation frequency control Uses parameters to define the frequency, during AC analysis. Parameter Scoping and Passing If you use parameters to define values in subcircuits, you need to create fewer similar cells, to provide enough functionality in your library. You can pass circuit parameters into hierarchical designs, and assign different values to the same parameter within individual cells, when you run simulation. For example, if you use parameters to set the initial state of a latch in its subcircuit definition, then you can override this initial default in the instance call. You need to create only one cell, to handle both initial state versions of the latch. HSPICE® User Guide: Simulation and Analysis B-2008.09 283 You can also use parameters to define the cell layout. For example, you can use parameters in a MOS inverter, to simulate a range of inverter sizes, with only one cell definition. Local instances of the cell can assign different values to the size parameter for the inverter. In HSPICE, you can also perform Monte Carlo analysis or optimization on a cell that uses parameters. How you handle hierarchical parameters depends on how you construct and analyze your cells. You can construct a design in which information flows from the top of the design, down into the lowest hierarchical levels. ■ To centralize the control at the top of the design hierarchy, set global parameters. ■ To construct a library of small cells that are individually controlled from within, set local parameters and build up to the block level. This section describes the scope of parameter names, and how HSPICE resolves naming conflicts between levels of hierarchy. Library Integrity Integrity is a fundamental requirement for any symbol library. Library integrity can be as simple as a consistent, intuitive name scheme, or as complex as libraries with built-in range checking. Library integrity might be poor if you use libraries from different vendors in a circuit design. Because names of circuit parameters are not standardized between vendors, two components can include the same parameter name for different functions. For example, one vendor might build a library that uses the name Tau as a parameter to control one or more subcircuits in their library. Another vendor might use Tau to control a different aspect of their library. If you set a global parameter named Tau to control one library, you also modify the behavior of the second library, which might not be the intent. If the scope of a higher-level parameter is global to all subcircuits at lower levels of the design hierarchy, higher-level definitions override lower-level parameter values with the same names. The scope of a lower-level parameter is local to the subcircuit where you define the parameter (but global to all subcircuits that are even lower in the design hierarchy). Local scoping rules in HSPICE prevent higher-level parameters from overriding lower-level parameters of the same name, when that is not desired. HSPICE® User Guide: Simulation and Analysis B-2008.09 284 Reusing Cells Parameter name problems also occur if different groups collaborate on a design. Global parameters prevail over local parameters, so all circuit designers must know the names of all parameters, even those used in sections of the design for which they are not responsible. This can lead to a large investment in standard libraries. To avoid this situation, use local parameter scoping, to encapsulate all information about a section of a design, within that section. Creating Parameters in a Library To ensure that the input netlist includes critical, user-supplied parameters when you run simulation, you can use “illegal defaults”—that is, defaults that cause the simulator to abort if you do not supply overrides for the defaults. If a library cell includes illegal defaults, you must provide a value for each instance of those cells. If you do not, the simulation aborts. For example, you might define a default MOSFET width of 0.0. HSPICE aborts because MOSFET models require this parameter. Example 1 * Subcircuit default definition .SUBCKT Inv A Y Wid=0 \$ Inherit illegal values by default mp1 <NodeList> <Model> L=1u W=’Wid*2’ mn1 <NodeList> <Model> L=1u W=Wid .ENDS * Invoke symbols in a design x1 A Y1 Inv \$ Bad! No widths specified x2 A Y2 Inv Wid=1u \$ Overrides illegal value for Width This simulation aborts on the x1 subcircuit instance because you never set the required Wid parameter on the subcircuit instance line. The x2 subcircuit simulates correctly. Additionally, the instances of the Inv cell are subject to accidental interference because the Wid global parameter is exposed outside the domain of the library. Anyone can specify an alternative value for the parameter, in another section of the library or the circuit design. This might prevent the simulation from catching the condition on x1. Example 2 In this example, the name of a global parameter conflicts with the internal library parameter named Wid. Another user might specify such a global HSPICE® User Guide: Simulation and Analysis B-2008.09 285 parameter, in a different library. In this example, the user of the library has specified a different meaning for the Wid parameter, to define an independent source. .Param Wid=5u \$ Default Pulse Width for source v1 Pulsed 0 Pulse ( 0v 5v 0u 0.1u 0.1u Wid 10u ) ... * Subcircuit default definition .SUBCKT Inv A Y Wid=0 \$ Inherit illegals by default mp1 <NodeList> <Model> L=1u W=’Wid*2’ mn1 <NodeList> <Model> L=1u W=Wid .Ends * Invoke symbols in a design x1 A Y1 Inv \$ Incorrect width! x2 A Y2 Inv Wid=1u \$ Incorrect! Both x1 and x2 \$ simulate with mp1=10u and \$ mn1=5u instead of 2u and 1u. Under global parameter scoping rules, simulation succeeds, but incorrectly. HSPICE does not warn that the x1 inverter has no assigned width because the global parameter definition for Wid overrides the subcircuit default. Note: Similarly, sweeping with different values of Wid dynamically changes both the Wid library internal parameter value, and the pulse width value to the Wid value of the current sweep. In global scoping, the highest-level name prevails, when resolving name conflicts. Local scoping uses the lowest-level name. When you use the parameter inheritance method, you can specify to use local scoping rules. When you use local scoping rules, the Example 2 netlist correctly aborts in x1 for W=0 (default Wid=0, in the .SUBCKT definition, has higher precedence, than the .PARAM statement). This results in the correct device sizes for x2. This change can affect your simulation results, if you intentionally or accidentally create a circuit such as the second one shown above. As an alternative to width testing in the Example 2 netlist, you can use .OPTION DEFW to achieve a limited version of library integrity. This option sets the default width for all MOS devices during a simulation. Part of the definition is still in the top-level circuit, so this method can still make unwanted changes to library values, without notification from the HSPICE simulator. HSPICE® User Guide: Simulation and Analysis B-2008.09 286 Table 21 compares the three primary methods for configuring libraries, to achieve required parameter checking for default MOS transistor widths. Table 21 Method Methods for Configuring Libraries Parameter Location Pros Cons Local On a .SUBCKT definition line Protects library from global circuit parameter definitions, unless you override it. Single location for default values. Global At the global level and on .SUBCKT definition lines Works with all HSPICE versions. An indiscreet user, another vendor assignment, or the intervening hierarchy can change the library. Cannot override a global value at a lower level. Special .OPTION DEFW statement Simple to do. Third-party libraries, or other sections of the design, might depend on .OPTION DEFW. String Parameter (HSPICE Only) HSPICE uses a special delimiter to identify string and double parameter types. The single quotes (‘), double quotes (“), or curly brackets ( {} ) do not work for these kinds of delimiters. Instead, use the sp1=str('string') keyword for an sp1 parameter definition and use the str(sp1) keyword for a string parameter instance. Example The following sample netlist shows an example of how you can use these definitions for various commands, keywords, parameters, and elements: HSPICE® User Guide: Simulation and Analysis B-2008.09 287 xibis1 vccq vss out in IBIS + IBIS_FILE=str('file1.ibs') IBIS_MODEL=str('model1') xibis2 vccq vss out in IBIS + IBIS_FILE=str('file2.ibs') IBIS_MODEL=str('model2') .subckt IBIS vccq vss out in + IBIS_FILE=str('file.ibs') + IBIS_MODEL=str('ibis_model') ven en 0 vcc BMCH vccq vss out in en v0dq0 vccq vss buffer=3 + file= str(IBIS_FILE) model=str(IBIS_MODEL) + typ=typ ramp_rwf=2 ramp_fwf=2 power=on .ends HSPICE supports these kinds of definitions and instances with the following netlist components: ■ .PARAM statements ■ .SUBCKT statements ■ S-parameter FQMODEL in both the S-parameter instance and S-parameter model and the TSTONEFILE keyword in the S-element ■ FILE and MODEL keywords ■ B-elements ■ W-element keywords RLGCFILE, UMODEL, FSMODEL, RLGCMODEL, TABLEMODEL, and SMODEL Note: The keywords MNAME and CITIFILE are not supported. String Parameters in Passive and Active Component Keywords You can include string parameters in all HSPICE passive and active component model name keywords. When defining a parameter that is a character string, the keyword str('string') is used to define the parameter. When an instance of the parameter is used, the parameter name is called as str(parameter_name). Syntax For passive elements: HSPICE® User Guide: Simulation and Analysis B-2008.09 288 Rxxx n1 n2 <mname <str(mname)>> Rval <TC1 <TC2><TC>> <SCALE=val> + <M=val> <AC=val> <DTEMP=val> <L=val> <W=val> <C=val> +<NOISE = val> Cxxx n1 n2 <mname <str(mname)>> <C = >capacitance <<TC1 = >val> + <<TC2 = >val> <SCALE = val> <IC = val> <M = val> + <W = val> <L = val> <DTEMP = val> Lxxx n1 n2 <L = >inductance <mname <str(mname)>> <<TC1 = >val> + <<TC2 = >val> <SCALE = val> <IC = val> <M = val> + <DTEMP = val> <R = val> For active elements, the model name can be defined using the original syntax, or string parameter model name syntax Dxxx nplus nminus str(mname) <<AREA = >area> <<PJ = >val> + <WP = val> <LP = val> <WM = val> <LM = val> <OFF> + <IC = vd> <M = val> <DTEMP = val> Qxxx nc nb ne <ns> str(mname) <area> <OFF> + <IC = vbeval,vceval> <M = val> <DTEMP = val> Jxxx nd ng ns <nb> str(mname) <<<AREA> = area | <W = val> + <L = val>> <OFF> <IC = vdsval,vgsval> <M = val> + <DTEMP = val> Mxxx nd ng ns <nb> str(mname) <<L = >length> <<W = >width> + <AD = val> AS = val> <PD = val> <PS = val> + <NRD = val> <NRS = val> <RDC = val> <RSC = val> <OFF> + <IC = vds,vgs,vbs> <M = val> <DTEMP = val> + <GEO = val> <DELVTO = val> Example .param mypmos=str('p') .param mynmos=str('n') .lib 'ltst.lib' TT .subckt circuit vout vin vdd nmod=str('nch')pmod=str('pch') m1 vout vin vdd vdd str(pmod) w=4u l=5u m2 vout vin 0 0 str(nmod) w=2u l=5u .ends circuit x1 vout vin vdd circuit dtemp=11 nmod=str(mynmos)pmod=str(mypmos) Parameter Defaults and Inheritance Use the .OPTION PARHIER parameter to specify scoping rules. Syntax: .OPTION PARHIER=< GLOBAL | LOCAL > HSPICE® User Guide: Simulation and Analysis B-2008.09 289 The default setting is GLOBAL. Example This example explicitly shows the difference between local and global scoping for using parameters in subcircuits. The input netlist includes the following: .OPTION parhier=<global | local> .PARAM DefPwid=1u .SUBCKT Inv a y DefPwid=2u DefNwid=1u Mp1 <MosPinList> pMosMod L=1.2u W=DefPwid Mn1 <MosPinList> nMosMod L=1.2u W=DefNwid .ENDS Set the .OPTION PARHIER=parameter scoping option to GLOBAL. The netlist also includes the following input statements: xInv0 a y0 Inv \$ override DefPwid default, \$ xInv0.Mp1 width=1u xInv1 a y1 Inv DefPwid=5u \$ override DefPwid=5u, \$ xInv1.Mp1 width=1u .measure tran Wid0 param=’lv2(xInv0.Mp1)’ \$ lv2 is the \$ template for .measure tran Wid1 param=’lv2(xInv1.Mp1)’ \$ the channel \$ width \$ ‘lv2(xInv1.Mp1)’ .ENDS Simulating this netlist produces the following results in the listing file: wid0=1.0000E-06 wid1=1.0000E-06 If you change the .OPTION PARHIER=parameter scoping option to LOCAL: xInv0 a y0 Inv \$ not override .param \$ DefPwid=2u, \$ xInv0.Mp1 width=2u xInv1 a y1 Inv DefPwid=5u \$ override .param \$ DefPwid=2u, \$ xInv1.Mp1 width=5u: .measure tran Wid0 param=’lv2(xInv0.Mp1)’\$ override the .measure tran Wid1 param=’lv2(xInv1.Mp1)’\$ global .PARAM ... Simulation produces the following results in the listing file: HSPICE® User Guide: Simulation and Analysis B-2008.09 290 Chapter 10: Parameters and Functions Parameter Scoping and Passing wid0=2.0000E-06 wid1=5.0000E-06 Parameter Passing Figure 26 on page 291 shows a flat representation of a hierarchical circuit, which contains three resistors. Each of the three resistors obtains its simulation time resistance from the Val parameter. The netlist defines the Val parameter in four places, with three different values. Sub1 + Sub2 Sub3 r1 r2 r3 1V - Figure 26 TEST OF PARHIER .OPTION list node post=2 + ingold=2 + parhier=<Local|Global> .PARAM Val=1 x1 n0 0 Sub1 .SubCkt Sub1 n1 n2 Val=1 r1 n1 n2 Val x2 n1 n2 Sub2 .Ends Sub1 .SubCkt Sub2 n1 n2 Val=2 r2 n1 n2 Val x3 n1 n2 Sub3 .Ends Sub2 .SubCkt Sub3 n1 n2 Val=3 r3 n1 n2 Val .Ends Sub3 .OP .END Hierarchical Parameter Passing Problem The total resistance of the chain has two possible solutions: 0.3333Ω and 0.5455Ω. You can use .OPTION PARHIER to specify which parameter value prevails, when you define parameters with the same name at different levels of the design hierarchy. Under global scoping rules, if names conflict, the top-level assignment .PARAM Val=1 overrides the subcircuit defaults, and the total is 0.3333Ω. Under local scoping rules, the lower level assignments prevail, and the total is 0.5455Ω (one, two, and three ohms in parallel). HSPICE® User Guide: Simulation and Analysis B-2008.09 291 Chapter 10: Parameters and Functions Parameter Scoping and Passing The example in Figure 26 produces the results in Table 22, based on how you set .OPTION PARHIER to local/global: Table 22 PARHIER=LOCAL vs. PARHIER=GLOBAL Results Element PARHIER=Local PARHIER=Global r1 1.0 1.0 r2 2.0 1.0 r3 3.0 1.0 Parameter Passing Solutions The following checklist determines whether you will see simulation differences when you use the default scoping rules. These checks are especially important if your netlists contain devices from multiple vendor libraries. ■ ■ Check your subcircuits for a .PARAM statement, within a .SUBCKT definition. ■ To check your circuits for global parameter definitions, use the .PARAM statement. ■ 292 Check your subcircuits for parameter defaults, on the .SUBCKT or .MACRO line. If any of the names from the first three checks are identical, set up two HSPICE simulation jobs: one with .OPTION PARHIER=GLOBAL, and one with .OPTION PARHIER=LOCAL. Then look for differences in the output. HSPICE® User Guide: Simulation and Analysis B-2008.09 11 11 Simulation Output Describes how to use output format statements and variables to display steady state, frequency, and time domain simulation results. You can also use output variables in behavioral circuit analysis, modeling, and simulation techniques. To display electrical specifications such as rise time, slew rate, amplifier gain, and current density, use the output format features. For descriptions of individual HSPICE commands referenced in this chapter, see the HSPICE Reference Manual: Commands and Control Options. These topics are organized in the following sections: ■ Overview of Output Statements ■ Displaying Simulation Results ■ Selecting Simulation Output Parameters ■ Specifying User-Defined Analysis (.MEASURE) ■ Expected State of Digital Output Signal (.DOUT) ■ Reusing Simulation Output as Input Stimuli (HSPICE Only) ■ Element Template Listings (HSPICE Only) ■ Redirecting the Simulation Output Results Files to a Different Directory ■ Using the HSPICE Output Converter Utility ■ Troubleshooting Issues Note: Parameter Storage Format (PSF) output is supported by all HSPICE analyses in the HSPICE integration to the CadenceTM Virtuoso® Analog Design Environment. HSPICE® User Guide: Simulation and Analysis B-2008.09 293 Chapter 11: Simulation Output Overview of Output Statements Note that the PSF and SDA writers used in HSPICE rely on libraries that are not currently available in 64 bit versions, and 64 bit HSPICE cannot link the 32-bit libraries. If you inspect the log file, you will see the message “**warning** 64bit cannot support option psf, artist or sda". Overview of Output Statements Output Commands The input netlist file contains output statements, including .PRINT, PROBE, .MEASURE, .DOUT, and .STIM. Each statement specifies the output variables, and the type of simulation result, to display—such as .DC, .AC, or .TRAN. When you specify .OPTION POST, HSPICE puts all output variables, referenced in .PRINT, .PROBE, .MEASURE, .DOUT, and .STIM statements into HSPICE output files. HSPICE RF supports only .OPTION POST, .OPTION PROBE, .PRINT, .PROBE, and .MEASURE statements. It does not support .DOUT or .STIM statements. Refer to the HSPICE Reference Manual: Commands and Control Options for information on all listed statements. CosmosScope provides high-resolution, post-simulation, and interactive display of waveforms. Table 23 Output Statements Output Statement Description .PRINT .PROBE Outputs data to post-processor output files, but not to the output listing (used with .OPTION PROBE, to limit output). See .PROBE. .MEASURE Prints the results of specific user-defined analyses (and postprocessor data, if you specify .OPTION POST), to the output listing file or HSPICE RF. See .MEASURE (or) .MEAS. .DOUT (HSPICE only 294 Prints numeric analysis results in the output listing file (and postprocessor data, if you specify .OPTION POST). See .PRINT. Specifies the expected final state of an output signal. See .DOUT or Expected State of Digital Output Signal (.DOUT). HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 11: Simulation Output Overview of Output Statements Table 23 Output Statements (Continued) Output Statement Description .STIM (HSPICE only) Specifies simulation results to transform to PWL, Data Card, or Digital Vector File format. See .STIM. Output Variables The output format statements require special output variables, to print or plot analysis results for nodal voltages and branch currents. HSPICE or HSPICE RF uses the following output variables: ■ DC and transient analysis ■ AC analysis ■ element template (HSPICE only) ■ .MEASURE statement ■ parametric analysis For HSPICE or HSPICE RF, DC and transient analysis displays: ■ individual nodal voltages: V(n1 [,n2]) ■ branch currents: I(Vxx) ■ element power dissipation: In(element) AC analysis displays imaginary and real components of a nodal voltage or branch current, and the magnitude and phase of a nodal voltage or branch current. AC analysis results also print impedance parameters, and input and output noise. Element template analysis displays element-specific nodal voltages, branch currents, element parameters, and the derivatives of the element’s node voltage, current, or charge. The .MEASURE statement variables define the electrical characteristics to measure in a .MEASURE statement analysis. Parametric analysis variables are mathematical expressions, which operate on nodal voltages, branch currents, element template variables (HSPICE only), or other parameters that you specify. Use these variables when you run HSPICE® User Guide: Simulation and Analysis B-2008.09 295 Chapter 11: Simulation Output Displaying Simulation Results behavioral analysis of simulation results. See Using Algebraic Expressions on page 278. Displaying Simulation Results The following section describes the statements that you can use to display simulation results for your specific requirements. .PRINT Statement The .PRINT statement specifies output variables for which HSPICE or HSPICE RF prints values. To simplify parsing of the output listings, HSPICE prints a single x in the first column, to indicate the beginning of the .PRINT output data. A single y in the first column indicates the end of the .PRINT output data. HSPICE RF prints the .PRINT output data to a separate file. You can include wildcards in .PRINT statements. You can also use the iall keyword in a .PRINT statement, to print all branch currents of all diode, BJT, JFET, or MOSFET elements in your circuit design. Example If your circuit contains four MOSFET elements (named m1, m2, m3, m4), then .PRINT iall (m*) is equivalent to .PRINT i(m1) i(m2) i(m3) i(m4). It prints the output currents of all four MOSFET elements. Statement Order HSPICE or HSPICE RF creates different .sw0 and .tr0 files, based on the order of the .PRINT and .DC statements. If you do not specify an analysis type for a .PRINT command, the type matches the last analysis command in the netlist, before the .PRINT statement. .PROBE Statement HSPICE or HSPICE RF usually saves all voltages, supply currents, and output variables. Set .OPTION PROBE, to save output variables only. Use the .PROBE statement to specify the quantities to print in the output listing. 296 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 11: Simulation Output Displaying Simulation Results If you are interested only in the output data file, and you do not want tabular or plot data in your listing file, set .OPTION PROBE and use .PROBE to select the values to save in the output listing. You can include wildcards in .PROBE statements. Using Wildcards in PRINT and PROBE Statements You can include wildcards in .PRINT and .PROBE statements. Refer to this example netlist in the discussion that follows: * test wildcard .option post v1 1 0 10 r1 1 n20 10 r20 n20 n21 10 r21 n21 0 10 .dc v1 1 10 1 ***Wildcard equivalent for: *.print i(r1) i(r20) i(r21) i(v1) .print i(*) ***Wildcard equivalent for: *.probe v(0) v(1) .probe v(?) ***Wildcard equivalent for: *.print v(n20) v(n21) .print v(n2?) ***Wildcard equivalent for: *.probe v(n20, 1) v(n21, 1) .probe v(n2*, 1) .end Supported Wildcard Templates (HSPICE only) v vm vr vi vp vdb vt i im ir ii ip idb it p pm pr pi pp pdb pt lxn<n> lvn<n> (n is a number 0~9) i1 im1 ir1 ii1 ip1 idb1 it1 i2 im2 ir2 ii2 ip2 idb2 it2 i3 im3 ir3 ii3 ip3 idb3 it3 i4 im4 ir4 ii4 ip4 idb4 it4 iall isub For detailed information about the templates, see .PRINT statement (see Selecting Simulation Output Parameters on page 300). HSPICE® User Guide: Simulation and Analysis B-2008.09 297 Chapter 11: Simulation Output Displaying Simulation Results When you use the wildcard i(*) in a .print or .probe statement, HSPICE will output all branch currents. For .AC analysis, to plot all currents for each valid AC output variable type, you can also use the following in statements: im(*) ir(*) ip(*) idb(*) it(*) In the preceding test case (named test wildcard), if you use an .AC statement instead of a .DC statement, any valid AC output variable types can be used with the wildcards v(n2?) and v(n2*,1). For example: vm(n2?) vr(n2?) vi(n2?) vp(n2?) vdb(n2?) vt(n2?) vm(n2*,1) vr(n2*,1) vi(n2*,1) vp(n2*,1) vdb(n2*,1) vt(n2*,1) To output the branch current at all terminals of a diode, BJT, JFET or MOSFET, use the output template iall. For example, iall(m*) is equivalent to: i1(m*) i2(m*) i3(m*) i4(m*) Print Control Options The codes that you can use to specify the element templates for output in HSPICE or HSPICE RF are: ■ .OPTION INGOLD for output in exponential form. ■ .OPTION POST to display plots using an interactive waveform viewer. ■ .OPTION ACCT to generate a detailed accounting report. HSPICE supports the following plot file formats: *.tr#, *.ac#, and *.sw#. If a plot fails to open, it is due to one of the following reasons: ■ The waveform file format is not supported. ■ The file format is not understood. ■ The file is not found. ■ The file is larger than max size of (x). Changing the File Descriptor Limit (HSPICE Only) A simulation that uses a large number of .ALTER statements might fail because of the limit on the number of file descriptors. For example, for a Sun workstation, the default number of file descriptors is 64, so a design with more than 50 .ALTER statements probably fails, with the following error message: 298 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 11: Simulation Output Displaying Simulation Results error could not open output spool file /tmp/tmp.nnn a critical system resource is inaccessible or exhausted To prevent this error on a Sun workstation, enter the following operating system command, before you start the simulation: limit descriptors 128 For platforms other than Sun workstations, ask your system administrator to help you increase the number of files that you can open concurrently. Printing the Subcircuit Output The following examples demonstrate how to print or plot voltages of nodes that are in subcircuit definitions, using .PRINT. Note: In the following example, you can substitute .PROBE, instead of .PRINT. Example 1 .GLOBAL vdd vss X1 1 2 3 nor2 X2 3 4 5 nor2 .SUBCKT nor2 A B Y .PRINT v(B) v(N1) \$ Print statement 1 M1 N1 A vdd vdd pch w=6u l=0.8u M2 Y B N1 vdd pch w=6u l=0.8u M3 Y A vss vss vss nch w=3u l=0.8u M4 Y B vss vss nch w=3u l=0.8u .ENDS Print statement 1 prints out the voltage on the B input node, and on the N1 internal node for every instance of the nor2 subcircuit. .PRINT v(1) v(X1.A) \$ Print statement 2 The preceding .PRINT statement specifies two ways to print the voltage on the A input of the X1 instance. .PRINT v(3) v(X1.Y) v(X2.A) \$ Print statement 3 The preceding .PRINT statement specifies three different ways to print the voltage at the Y output of the X1 instance (or the A input of the X2 instance). .PRINT v(X2.N1) \$ Print statement 4 HSPICE® User Guide: Simulation and Analysis B-2008.09 299 Chapter 11: Simulation Output Selecting Simulation Output Parameters The preceding .PRINT statement prints the voltage on the N1 internal node of the X2 instance. .PRINT i(X1.M1) \$ Print statement 5 The preceding .PRINT statement prints out the drain-to-source current, through the M1 MOSFET in the X1 instance. Example 2 X1 5 6 YYY .SUBCKT YYY 15 16 X2 16 36 ZZZ R1 15 25 1 R2 25 16 1 .ENDS .SUBCKT ZZZ 16 36 C1 16 0 10P R3 36 56 10K C2 56 0 1P .ENDS .PRINT V(X1.25) V(X1.X2.56) V(6) Value Description V(X1.25) Local node to the YYY subcircuit definition, which the X1 subcircuit calls. V(X1.X2.56) Local node to the ZZZ subcircuit. The X2 subcircuit calls this node; X1 calls X2. V(6) Voltage of node 16, in the X1 instance of the YYY subcircuit. This example prints voltage analysis results at node 56, within the X2 and X1 subcircuits. The full path, X1.X2.56, specifies that node 56 is within the X2 subcircuit, which in turn is within the X1 subcircuit. Selecting Simulation Output Parameters Parameters provide the appropriate simulation output. To define simulation parameters, use the .OPTION and .MEASURE statements, and define specific variable elements. 300 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 11: Simulation Output Selecting Simulation Output Parameters DC and Transient Output Variables ■ Voltage differences between specified nodes (or between one specified node and ground). ■ Current output for an independent voltage source. ■ Current output for any element. ■ Current output for a subcircuit pin. ■ Element templates (HSPICE only). For each device type, the templates contain: • values of variables that you set • state variables • element charges • capacitance currents • capacitances • derivatives Print Control Options on page 298 summarizes the codes that you can use, to specify the element templates for output in HSPICE or HSPICE RF. Nodal Capacitance Output Syntax Cap(nxxx) For nodal capacitance output, HSPICE prints or plots the capacitance of the specified node nxxxx. Example .print dc Cap(5) Cap(6) HSPICE® User Guide: Simulation and Analysis B-2008.09 301 Chapter 11: Simulation Output Selecting Simulation Output Parameters Nodal Voltage Syntax V(n1<,n2>) Parameter Description n1, n2 HSPICE or HSPICE RF prints or plots the voltage difference (n1-n2) between the specified nodes. If you omit n2, HSPICE or HSPICE RF prints or plots the voltage difference between n1 and ground (node 0). Current: Independent Voltage Sources Syntax I(Vxxx) Parameter Description Vxxx Voltage source element name. If an independent power supply is within a subcircuit, then to access its current output, append a dot and the subcircuit name to the element name. For example, I(X1.Vxxx). Example .PRINT TRAN I(VIN) .PRINT DC I(X1.VSRC) .PRINT DC I(XSUB.XSUBSUB.VY) Current: Element Branches Syntax In(Wwww) Iall(Wwww) Parameter n 302 Description Node position number, in the element statement. For example, if the element contains four nodes, I3 is the branch current output for the third node. If you do not specify n, HSPICE or HSPICE RF assumes the first node. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 11: Simulation Output Selecting Simulation Output Parameters Parameter Description Wwww Element name. To access current output for an element in a subcircuit, append a dot and the subcircuit name to the element name. For example, I3(X1.Wwww). Iall (Wwww) An alias just for diode, BJT, JFET, and MOSFET devices. ■ ■ If Wwww is a diode, it is equivalent to: I1(Wwww) I2(Wwww). If Wwww is one of the other device types, it is equivalent to: I1(Wwww) I2(Wwww) I3(Wwww) I4(Wwww) Example 1 I1(R1) This example specifies the current through the first R1 resistor node. Example 2 I4(X1.M1) This example specifies the current, through the fourth node (the substrate node) of the M1 MOSFET, defined in the X1 subcircuit. Example 3 I2(Q1) The last example specifies the current, through the second node (the base node) of the Q1 bipolar transistor. To define each branch circuit, use a single element statement. When HSPICE or HSPICE RF evaluates branch currents, it inserts a zero-volt power supply, in series with branch elements. If HSPICE cannot interpret a .PRINT statement that contains a branch current, it generates a warning. Branch current direction for the elements in Figure 27 through Figure 32 is defined in terms of arrow notation (current direction), and node position number (terminal type). HSPICE® User Guide: Simulation and Analysis B-2008.09 303 Chapter 11: Simulation Output Selecting Simulation Output Parameters node1 I1 (R1) R1 node2 I2 (R1) Figure 27 Resistor (node1, node2) node1 I1(L1) I1(C1) I2(L1) I2(C1) node2 Figure 28 Inductor (node1, node2); capacitor (node 1, node2) I1 (D1) I2 (D1) Figure 29 304 node1 (anode, P-type, + node) node2 (anode, N-type, - node) Diode (node1, node2) HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 11: Simulation Output Selecting Simulation Output Parameters node1 (drain node) I1 (J1) node2 (gate node) I2 (J1) Figure 30 node2 (source node) I3 (J1) JFET (node1, node2, node3) - n-channel node1 (drain node) I1 (M1) node2 (gate node) node4 (substrate node) I4 (M1) I2 (M1) node3 (source node) I3 (M1) Figure 31 MOSFET (node1, node2, node3, node4) - n-channel node1 (collector node) I1 (Q1) node2 (base node) I2 (Q1) node4 (substrate node) I4 (Q1) node3 (emitter node) I3 (Q1) Figure 32 BJT (node1, node2, node3, node4) - npn HSPICE® User Guide: Simulation and Analysis B-2008.09 305 Chapter 11: Simulation Output Selecting Simulation Output Parameters Current: Subcircuit Pin Syntax ISUB(X****.****) Example .PROBE ISUB(X1.PIN1) Power Output For power calculations, HSPICE or HSPICE RF computes dissipated or stored power in each passive element (R, L, C), and source (V, I, G, E, F, and H). To compute this power, HSPICE or HSPICE RF multiplies the voltage across an element, and its corresponding branch current. However, for semiconductor devices, HSPICE or HSPICE RF calculates only the dissipated power. It excludes the power stored in the device junction or parasitic capacitances from the device power computation. The following sections show equations for calculating the power that different types of devices dissipate. HSPICE or HSPICE RF also computes the total power dissipated in the circuit, which is the sum of the power dissipated in: ■ Devices ■ Resistors ■ Independent current sources ■ All dependent sources For hierarchical designs, HSPICE or HSPICE RF also computes the power dissipation for each subcircuit. Note: For the total power (dissipated power + stored power), HSPICE or HSPICE RF does not add the power of each independent source (voltage and current sources). Wildcard Support Wildcard support is available for current subcircuit pins in single and multiple hierarchies using asterisk (*) and question mark (?) characters. For example: Single Hierarchy .print isub(x1.*) isub(x1.a?) 306 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 11: Simulation Output Selecting Simulation Output Parameters Multi-level Hierarchy .print isub(x1.x2.*) isub(x1.x?.a?) Print Power .PRINT <DC | TRAN> P(element_or_subcircuit_name)POWER HSPICE calculates power only for transient and DC sweep analyses. Use the .MEASURE statement to compute the average, RMS, minimum, maximum, and peak-to-peak value of the power. The POWER keyword invokes the total power dissipation output. HSPICE RF supports p(instance) but not the POWER variable in DC/transient analysis. Example .PRINT TRAN P(M1) P(VIN) P(CLOAD) POWER .PRINT TRAN P(Q1) P(DIO) P(J10) POWER .PRINT TRAN POWER \$ Total transient analysis * power dissipation .PRINT DC POWER P(IIN) P(RLOAD) P(R1) .PRINT DC POWER P(V1) P(RLOAD) P(VS) .PRINT TRAN P(Xf1) P(Xf1.Xh1) Diode Power Dissipation Pd = Vpp' ⋅ ( Ido + Icap ) + Vp' n ⋅ Ido Parameter Description Pd Power dissipated in the diode. Ido DC component of the diode current. Icap Capacitive component of the diode current. Vp'n Voltage across the junction. Vpp' Voltage across the series resistance, RS. HSPICE® User Guide: Simulation and Analysis B-2008.09 307 Chapter 11: Simulation Output Selecting Simulation Output Parameters BJT Power Dissipation ■ Vertical Pd = Vc' e' ⋅ Ico + Vb' e' ⋅ Ibo + Vcc' ⋅ Ictot + Vee' ⋅ Ietot + Vsc' ⋅ Iso – Vcc' ⋅ Istot ■ Lateral Pd = Vc' e' ⋅ Ico + Vb' e' ⋅ Ibo + Vcc' ⋅ Ictot + Vbb' ⋅ Ibtot + Vee' ⋅ Ietot Vsb' ⋅ Iso – Vbb' ⋅ Istot Parameter Ibo DC component of the base current. Ico DC component of the collector current. Iso DC component of the substrate current. Pd Power dissipated in a BJT. Ibtot Total base current (excluding the substrate current). Ictot Total collector current (excluding the substrate current). Ietot Total emitter current. Istot Total substrate current. Vb'e' Voltage across the base-emitter junction. Vbb' Voltage across the series base resistance, RB. Vc'e' Voltage across the collector-emitter terminals. Vcc' Voltage across the series collector resistance, RC. Vee' Voltage across the series emitter resistance, RE. Vsb' Voltage across the substrate-base junction. Vsc' 308 Description Voltage across the substrate-collector junction. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 11: Simulation Output Selecting Simulation Output Parameters JFET Power Dissipation Pd = Vd' s' ⋅ Ido + Vgd' ⋅ Igdo + Vgs' ⋅ Igso + Vs' s ⋅ ( Ido + Igso + Icgs ) + Vdd' ⋅ ( Ido – Igdo – Icgd ) Parameter Description Icgd Capacitive component of the gate-drain junction current. Icgs Capacitive component of the gate-source junction current. Ido DC component of the drain current. Igdo DC component of the gate-drain junction current. Igso DC component of the gate-source junction current. Pd Power dissipated in a JFET. Vd's' Voltage across the internal drain-source terminals. Vdd' Voltage across the series drain resistance, RD. Vgd' Voltage across the gate-drain junction. Vgs' Voltage across the gate-source junction. Vs's Voltage across the series source resistance, RS. MOSFET Power Dissipation Pd = Vd' s' ⋅ Ido + Vbd' ⋅ Ibdo + Vbs' ⋅ Ibso + Vs' s ⋅ ( Ido + Ibso + Icbs + Icgs ) + Vdd' ⋅ ( Ido – Ibdo – Icbd – Icgd ) Parameter Description Ibdo DC component of the bulk-drain junction current. Ibso DC component of the bulk-source junction current. Icbd Capacitive component of the bulk-drain junction current. Icbs Capacitive component of the bulk-source junction current. HSPICE® User Guide: Simulation and Analysis B-2008.09 309 Chapter 11: Simulation Output Selecting Simulation Output Parameters Parameter Description Icgd Capacitive component of the gate-drain current. Icgs Capacitive component of the gate-source current. Ido DC component of the drain current. Pd Power dissipated in the MOSFET. Vbd' Voltage across the bulk-drain junction. Vbs' Voltage across the bulk-source junction. Vd's' Voltage across the internal drain-source terminals. Vdd' Voltage across the series drain resistance, RD. Vs's Voltage across the series source resistance, RS. AC Analysis Output Variables Output variables for AC analysis include: ■ Voltage differences between specified nodes (or between one specified node and ground). ■ Current output for an independent voltage source. ■ Current output for a subcircuit pin. ■ Element branch current. ■ Impedance (Z), admittance (Y), hybrid (H), and scattering (S) parameters. ■ Input and output impedance, and admittance. Table 24 lists AC output variable types. In this table, the type symbol is appended to the variable symbol, to form the output variable name. For example, VI is the imaginary part of the voltage, or IM is the magnitude of the current. 310 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 11: Simulation Output Selecting Simulation Output Parameters Table 24 AC Output Variable Types Type Symbol Variable Type DB decibel I imaginary part M magnitude P phase R real part T group delay Specify real or imaginary parts, magnitude, phase, decibels, and group delay for voltages and currents. Nodal Capacitance Output Syntax Cap(nxxx) For nodal capacitance output, HSPICE prints the capacitance of the specified node nxxxx. Example .print ac Cap(5) Cap(6) Nodal Voltage Syntax Vz(n1<,n2>) Parameter Description z Specifies the voltage output type (see Table 24 on page 311) n1, n2 Specifies node names. If you omit n2, HSPICE or HSPICE RF assumes ground (node 0). HSPICE® User Guide: Simulation and Analysis B-2008.09 311 Chapter 11: Simulation Output Selecting Simulation Output Parameters Example This example applies to HSPICE, but not HSPICE RF. It prints the magnitude of the AC voltage of node 5, using the VM output variable. HSPICE uses the VDB output variable to print the voltage at node 5, and uses the VP output variable to print the phase of the nodal voltage at node 5. .PRINT AC VM(5) VDB(5) VP(5) HSPICE and SPICE Methods for Producing Complex Results To produce complex results, an AC analysis uses either the SPICE or HSPICE method, and the .OPTION ACOUT control option, to calculate the values of real or imaginary parts for complex voltages of AC analysis, and their magnitude, phase, decibel, and group delay values. The default for HSPICE is ACOUT=1. To use the SPICE method, set ACOUT=0. A typical use of the SPICE method is to calculate the nodal vector difference, when comparing adjacent nodes in a circuit. You can use this method to find the phase or magnitude across a capacitor, inductor, or semiconductor device. Use the HSPICE method to calculate an inter-stage gain in a circuit (such as an amplifier circuit), and to compare its gain, phase, and magnitude. The following examples define the AC analysis output variables for the HSPICE method, and then for the SPICE method. HSPICE Method Example: Real and imaginary: VR(N1,N2)= REAL [V(N1,0)] - REAL [V(N2,0)] VI(N1,N2)= IMAG [V(N1,0)] - IMAG [V(N2,0)] Magnitude: VM(N1,0)= [VR(N1,0)2 + VI(N1,0)2]0.5 VM(N2,0)= [VR(N2,0)2 + VI(N2,0)2]0.5 VM(N1,N2)= VM(N1,0) - VM(N2,0) Phase: VP(N1,0)= ARCTAN[VI(N1,0)/VR(N1,0)] VP(N2,0)= ARCTAN[VI(N2,0)/VR(N2,0)] VP(N1,N2)= VP(N1,0) - VP(N2,0) Decibel: VDB(N1,0)=20 ⋅ LOG10[VM(N1,0)] VDB(N1,N2)= 20 ⋅ LOG10(VM(N1,0)/VM(N2,0)) 312 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 11: Simulation Output Selecting Simulation Output Parameters SPICE Method Example: Real and imaginary: VR(N1,N2)=REAL [V(N1,0) - V(N2,0)] VI(N1,N2)=IMAG [V(N1,0) - V(N2,0)] Magnitude: VM(N1,N2)=[VR(N1,N2)2+VI(N1,N2)2]0.5 Phase: VP(N1,N2)=ARCTAN[VI(N1,N2)/VR(N1,N2)] Decibel: VDB(N1,N2)=20 ⋅ LOG10[VM(N1,N2)] Current: Independent Voltage Sources Syntax Iz(Vxxx) Parameter Description z Current output type (see Table 24 on page 311). Vxxx Voltage source element name. If an independent power supply is within a subcircuit, then to access its current output, append a dot and the subcircuit name to the element name. For example, IM(X1.Vxxx). Example .PRINT AC IR(V1) IM(VN2B) IP(X1.X2.VSRC) Current: Element Branches Syntax Izn(Wwww) Parameter Description z Current output type (see Table 24 on page 311). HSPICE® User Guide: Simulation and Analysis B-2008.09 313 Chapter 11: Simulation Output Selecting Simulation Output Parameters Parameter Description n Node position number, in the element statement. For example, if the element contains four nodes, IM3 denotes the magnitude of the branch current output for the third node. Wwww Element name. If the element is within a subcircuit, then to access its current output, append a dot and the subcircuit name to the element name. For example, IM3(X1.Wwww). .PRINT AC IP1(Q5) IM1(Q5) IDB4(X1.M1) If you use the form In(Xxxx) for AC analysis output, then HSPICE or HSPICE RF prints the magnitude value, IMn(Xxxx). Current: Subcircuit Pin Syntax ISUB(X****.****) Example .PROBE ISUB(X1.PIN1) Group Time Delay The TD group time delay is associated with AC analysis. TD is the negative derivative of the phase in radians, with respect to radian frequency. HSPICE or HSPICE RF uses the difference method to compute TD: 1 - ( phase 2 – phase 1 ) TD = – -------- ⋅ ----------------------------------------------(f2 – f1) 360 phase1 and phase2 are the phases (in degrees) of the specified signal, at the f1 and f2 frequencies (in hertz). Syntax .PRINT AC VT(10) VT(2,25) IT(RL) .PRINT AC IT1(Q1) IT3(M15) IT(D1) Note: Because the phase has a discontinuity every 360°, TD shows the same discontinuity, even though TD is continuous. 314 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 11: Simulation Output Selecting Simulation Output Parameters Example INTEG.SP ACTIVE INTEGRATOR ****** INPUT LISTING ****** V1 1 0 .5 AC 1 R1 1 2 2K C1 2 3 5NF E3 3 0 2 0 -1000.0 .AC DEC 15 1K 100K .PRINT AC VT(3) (0,4U) .END VP(3) Network Syntax Xij (z), ZIN(z), ZOUT(z), YIN(z), YOUT(z) Parameter Description X Specifies Z (impedance), Y (admittance), H (hybrid), or S (scattering). ij i and j can be 1 or 2. They identify the matrix parameter to print. z Output type (see Table 24 on page 311). If you omit z, HSPICE or HSPICE RF prints the magnitude of the output variable. ZIN Input impedance. For a one-port network, ZIN, Z11, and H11 are the same. ZOUT Output impedance. YIN Input admittance. For a one-port network, YIN and Y11 are the same. YOUT Output admittance. Example .PRINT .PRINT .PRINT AC AC AC Z11(R) ZIN(R) S22(M) Z12(R) ZIN(I) S22(P) Y21(I) YOUT(M) S21(R) Y22 S11 S11(DB) YOUT(P) H11(M) H21(P) H12(R) Noise and Distortion This section describes the variables used for noise and distortion analysis. HSPICE® User Guide: Simulation and Analysis B-2008.09 315 Chapter 11: Simulation Output Selecting Simulation Output Parameters Syntax ovar <(z)> Parameter Description ovar Noise and distortion analysis parameter. It can be ONOISE (output noise), INOISE (equivalent input noise), or any of the distortion analysis parameters (HD2, HD3, SIM2, DIM2, DIM3). z Output type (only for distortion). If you omit z, HSPICE or HSPICE RF outputs the magnitude of the output variable. Example .PRINT DISTO HD2(M) HD2(DB) Prints the magnitude and decibel values of the second harmonic distortion component, through the load resistor that you specified in the .DISTO statement (not shown). You cannot use the .DISTO statement in HSPICE RF. .PRINT NOISE INOISE ONOISE Note: You can specify the noise and distortion output variable, and other AC output variables, in the .PRINT AC statements. Element Template Output (HSPICE Only) The .PRINT, and .PROBE statements use element templates to output userinput parameters, state variables, stored charges, capacitor currents, capacitances, and derivatives of variables. Element templates are listed at the end of this chapter. Syntax Elname:Property Parameter Elname Name of the element. Property 316 Description Property name of an element, such as a user-input parameter, state variable, stored charge, capacitance current, capacitance, or derivative of a variable. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 11: Simulation Output Specifying User-Defined Analysis (.MEASURE) The alias is: LVnn(Elname) LXnn(Elname) Parameter Description LV Form to obtain output of user-input parameters, and state variables. LX Form to obtain output of stored charges, capacitor currents, capacitances, and derivatives of variables. nn Code number for the desired parameter (listed in tables in this section). Elname Name of the element. Example .PRINT TRAN V(1,12) I(X2.VSIN) I2(Q3) DI01:GD .PRINT TRAN X2.M1:CGGBO M1:CGDBO X2.M1:CGSBO Specifying User-Defined Analysis (.MEASURE) Use the .MEASURE statement to modify information, and to define the results of successive HSPICE or HSPICE RF simulations. Computing the measurement results is based on postprocessing output. If you use the INTERP option to reduce the size of the postprocessing output, then the measurement results can contain interpolation errors. For more information, see .OPTION INTERP in the HSPICE Reference Manual: Commands and Control Options. Fundamental measurement modes in HSPICE are: ■ Rise, fall, and delay ■ Find-when ■ Equation evaluation ■ Average, RMS, min, max, and peak-to-peak ■ Integral evaluation ■ Derivative evaluation ■ Relative error HSPICE® User Guide: Simulation and Analysis B-2008.09 317 Chapter 11: Simulation Output Specifying User-Defined Analysis (.MEASURE) If a .MEASURE statement does not execute, then HSPICE or HSPICE RF writes 0.0e0 in the .mt# file as the .MEASURE result, and writes FAILED in the output listing file. Use .OPTION MEASFAIL to write results to the .mt#, .ms#, or .ma# files. For more information, see .OPTION MEASFAIL in the HSPICE Reference Manual: Commands and Control Options. Note: The .mt# format consists of 72 characters in a line and fields that contain 16 characters each. To control the output variables, listed in .MEASURE statements, use the .PUTMEAS option. For more information, see the .OPTION PUTMEAS option in the HSPICE Reference Manual: Commands and Control Options. Note: If a .measure statement uses the result of previous .meas statement, then the calculation starts when the previous result is found. Until the previous result is found, it outputs zero. .MEASURE Statement Order The .MEASURE statement matches the last analysis command in the netlist before the .MEASURE statement. Example .tran 20p 1.0n sweep sigma -3 3 0.5 .tran 20p 1.0n sweep monte=20 .meas mover max v(2,1) In this example, .meas matches the second .tran statement and generates only one measure output file. .MEASURE Parameter Types You cannot use measurement parameter results that the .PARAM statements in .SUBCKT blocks produce, outside of the subcircuit. That is, you cannot pass any measurement parameters defined in .SUBCKT statements, as bottom-up parameters in hierarchical designs. Measurement parameter names must not conflict with standard parameter names. HSPICE or HSPICE RF issues an error message, if it encounters a measurement parameter with the same name as a standard parameter definition. 318 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 11: Simulation Output Specifying User-Defined Analysis (.MEASURE) To prevent .MEASURE statement parameters from overwriting parameter values in other statements, HSPICE or HSPICE RF keeps track of parameter types. If you use the same parameter name in both a .MEASURE statement and a .PARAM statement at the same hierarchical level, simulation terminates and reports an error. No error occurs if parameter assignments are at different hierarchical levels. .PRINT statements that occur at different levels, do not print hierarchical information for parameter name headings. Example In HSPICE RF simulation output, you cannot apply .MEASURE to waveforms generated from another .MEASURE statement in a parameter sweep. The following example illustrates how HSPICE or HSPICE RF handles .MEASURE statement parameters. ... .MEASURE tran length TRIG v(clk) VAL=1.4 + TD=11ns RISE=1 TARGv(neq) VAL=1.4 TD=11ns + RISE=1 .SUBCKT path out in width=0.9u length=600u + rm1 in m1 m2mg w='width' l='length/6' ... .ENDS In the above listing, the length in the resistor statement: rm1 in m1 m2mg w='width' l='length/6' does not inherit its value from length in the .MEASURE statement: .MEASURE tran length ... because they are of different types. The correct value of l in rm1 should be: l=length/6=100u The value should not be derived from a measured value in transient analysis. FIND and WHEN Functions The FIND and WHEN functions of the .MEASURE statement specify to measure: HSPICE® User Guide: Simulation and Analysis B-2008.09 319 Chapter 11: Simulation Output Specifying User-Defined Analysis (.MEASURE) ■ Any independent variables (time, frequency, parameter). ■ Any dependent variables (voltage or current for example). ■ Derivative of a dependent variable, if a specific event occurs. You can use these measure statements in unity gain frequency or phase measurements. You can also use these statements to measure the time, frequency, or any parameter value: ■ When two signals cross each other. ■ When a signal crosses a constant value. The measurement starts after a specified time delay, TD. To find a specific event, set RISE, FALL, or CROSS to a value (or parameter), or specify LAST for the last event. LAST is a reserved word; you cannot use it as a parameter name in the above measure statements. For definitions of parameters of the measure statement, see Displaying Simulation Results on page 296. Equation Evaluation Use the Equation Evaluation form of the .MEASURE statement to evaluate an equation, that is a function of the results of previous .MEASURE statements. The equation must not be a function of node voltages or branch currents. The expression option is an arithmetic expression that uses results from other prior .MEASURE statements. If equation or expression includes node voltages or branch currents, Unexpected results may incur. Average, EM_AVG, RMS, MIN, MAX, INTEG, and PP Average (AVG), RMS, MIN, MAX, and peak-to-peak (PP) measurement modes report statistical functions of the output variable, rather than analysis values. ■ ■ RMS divides the square root of the area under the output variable square, by the period of interest. ■ 320 AVG calculates the area under an output variable, divided by the periods of interest. MIN reports the minimum value of the output function, over the specified interval. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 11: Simulation Output Specifying User-Defined Analysis (.MEASURE) ■ MAX reports the maximum value of the output function, over the specified interval. ■ PP (peak-to-peak) reports the maximum value, minus the minimum value, over the specified interval. AVG, RMS, and INTEG have no meaning in a DC data sweep, so if you use them, HSPICE or HSPICE RF issues a warning message. ■ EM_AVG Calculates the average electromigration current. For a symmetric bipolar waveform, the current is: I_avg (0, T/2) - R*Iavg (T/2, T), where R is the recovery factor specified using .option em_recovery. Wildcards are also supported during this measurement. Measuring Recovered Electromigration The .MEAS keyword,EM_AVG, enables you to calculate “recovered” average current due to electromigration. Recovered average current is specially meaningful for bipolar currents (such as output of the inverter), as the mathematical average for such a waveform will be zero.The keyword uses the From-To measurement function to provide a range to measure. For example: .measure tran em em_avg I(out) from=5n to=50n where out is the node at which the measurement is taken. The example does the following operations: 1. Finds the average of all the positive currents (Ipos_avg) from 5ns to 50ns. 2. Finds the average (absolute value) of all the negative currents (Ineg_avg) from 5ns to 50ns. 3. Does the operation “Ipos_avg - R*Ineg_avg”. Where R is a user-provided coefficient using .option em_recovery=value. The default value of em_recovery is 1. See .OPTION EM_RECOVERY in the HSPICE Reference Manual: Commands and Control Options. For this feature HSPICE also supports wildcards (*) during em_avg measurement. For example: .meas tran em em_avg I(m*) from=10n to=100n HSPICE® User Guide: Simulation and Analysis B-2008.09 321 Chapter 11: Simulation Output Specifying User-Defined Analysis (.MEASURE) INTEGRAL Function The INTEGRAL function reports the integral of an output variable, over a specified period. DERIVATIVE Function The DERIVATIVE function provides the derivative of: ■ An output variable, at a specified time or frequency. ■ Any sweep variable, depending on the type of analysis. ■ A specified output variable, when some specific event occurs. In the following HSPICE RF example, the SLEW measurement provides the slope of V(OUT) during the first time, when V(1) is 90% of VDD. .MEAS TRAN SLEW DERIV V(OUT) WHEN V(1)=‘0.90*VDD’ ERROR Function The relative error function reports the relative difference between two output variables. You can use this format in optimization and curve-fitting of measured data. The relative error format specifies the variable to measure and calculate from the .PARAM variable. To calculate the relative error between the two, HSPICE or HSPICE RF uses the ERR, ERR1, ERR2, or ERR3 function. With this format, you can specify a group of parameters to vary, to match the calculated value and the measured data. Error Equations ERR 1. ERR sums the squares of (M-C)/max (M, MINVAL) for each point. 2. It then divides by the number of points. 3. Finally, it calculates the square root of the result. • • C (calc_var) is the calculated value of the device or circuit response. • 322 M (meas_var) is the measured value of the device or circuit response. NPTS is the number of data points. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 11: Simulation Output Specifying User-Defined Analysis (.MEASURE) NPTS 1ERR = -------------- ⋅ NPTS 1/2 2 Mi – Ci ⎛ ---------------------------------------------⎞ ∑ ⎝ max (MINVAL,Mi)⎠ i=1 ERR1 ERR1 computes the relative error at each point. For NPTS points, HSPICE or HSPICE RF calculates NPTS ERR1 error functions. For device characterization, the ERR1 approach is more efficient than the other error functions (ERR, ERR2, ERR3). Mi – Ci ERR 1 i = --------------------------------------------- , i=1,NPTS max (MINVAL,M i) HSPICE or HSPICE RF does not print out each calculated ERR1 value. When you set the ERR1 option, HSPICE or HSPICE RF calculates an ERR value, as follows: NPTS 1ERR = -------------- ⋅ NPTS 1/2 ∑ ERR 1i2 i=1 ERR2 This option computes the absolute relative error, at each point. For NPTS points, HSPICE or HSPICE RF calls NPTS error functions. Mi – Ci ERR 2 i = --------------------------------------------- , i=1,NPTS max (MINVAL,M i) The returned value printed for ERR2 is: NPTS 1ERR = -------------- ⋅ NPTS ∑ ERR 2i i=1 ERR3 M ±log -----i Ci ERR 3 i = ---------------------------------------------------------------- , i=1,NPTS log [ max (MINVAL, M i ) ] The + and - signs correspond to a positive and negative M/C ratio. HSPICE® User Guide: Simulation and Analysis B-2008.09 323 Chapter 11: Simulation Output Expected State of Digital Output Signal (.DOUT) Note: If the M measured value is less than MINVAL, HSPICE or HSPICE RF uses MINVAL instead. If the absolute value of M is less than the IGNOR or YMIN value, or greater than the YMAX value, the error calculation does not consider this point. Expected State of Digital Output Signal (.DOUT) The digital output (.DOUT) statement specifies the expected final state of an output signal (HSPICE only). During simulation, HSPICE compares the simulated results with the expected output vector. An error results if states are different. The .DOUT statement uses either of two syntaxes. In both syntaxes, the time and state parameters define the expected output of the nd node. ■ The first syntax specifies a single threshold voltage, VTH. Any voltage level above VTH is high; any level below VTH is low. .DOUT nd VTH (time state time state) where: nd is the node name VTH is the single voltage threshold time is an absolute time-point state is one of the following expected conditions of the nd node, at the specified time: 0 expect 1 expect ONE, HIGH else ■ ZERO, LOW Don’t care The second syntax defines a threshold for both a logic high (VHI) and low (VLO). .DOUT nd VLO VHI (time state <time state>) where: nd is the node name VLO is the voltage of the logic low state VHI is the voltage of the logic high state time is an absolute time-point 324 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 11: Simulation Output Expected State of Digital Output Signal (.DOUT) state is one of the following expected conditions of the nd node, at the specified time: 0 expect ZERO, LOW 1 expect ONE, HIGH else Don’t care Note: If you specify both syntaxes (VTH, plus VHI and VLO), then HSPICE processes only VTH, and ignores VHI and VLO. For both cases, the time, state pair describes the expected output. During simulation, HSPICE compares the simulated results against the expected output vector. If the states are different, HSPICE reports an error. The legal values for state are: ■ 0 Expect ZERO. ■ 1 Expect ONE. ■ X, x Do not care. ■ U, u Do not care ■ Z, z Expect HIGH IMPEDANCE (do not care). Example The .PARAM statement in the following example sets the value of the VTH variable to 3. The .DOUT statement, operating on the node1 node, uses VTH as its threshold voltage. .PARAM VTH = 3.0 .DOUT node1 VTH(0.0n 0 1.0n 1 + 2.0n X 3.0n U 4.0n Z 5.0n 0) When node1 is above 3V, it is considered a logic 1; otherwise, it is a logic 0. ■ At 0ns, the expected state of node1 is logic-low ■ At 1ns, the expected state is logic-high ■ At 2ns, 3ns, and 4ns, the expected state is “do not care” ■ At 5ns, the expected state is again logic-low HSPICE® User Guide: Simulation and Analysis B-2008.09 325 Chapter 11: Simulation Output Reusing Simulation Output as Input Stimuli (HSPICE Only) Reusing Simulation Output as Input Stimuli (HSPICE Only) You can use the .STIM statement to reuse the results (output) of one simulation, as input stimuli in a new simulation. Note: .STIM is an abbreviation of .STIMULI. You can use either form to specify this statement in HSPICE. The .STIM statement specifies: ■ Expected stimulus (PWL source, data card, or VEC file). ■ Signals to transform. ■ Independent variables. One .STIM statement produces one corresponding output file. To control the precision and data format, you can use the same options as you would in a normal simulation. For example: .option numdgt=6 \$ sets precision, range is 0 to 10, numdgt=4 is the default .option ingold=0 \$ sets format, 0=eng 1=combined 2=exponential Note that these settings these affect how data is printed out for your entire testcase. There is no way to only affect the .STIM command because the output of the .STIM command is taken from the simulation data. For the syntax and description of the .STIM statement, see the .STIM command in the HSPICE Reference Manual: Commands and Control Options. Reusing the PAR(...) output as input to other elements You can use the par(...) output as the input voltage to another elements. For example: .print tran v(5) par('5*cos(6.28*v(10)*v(5)*k/360)') You can use the signal either as the input to another element in the same simulation (see Example 1), or you can save the signal and use it as input in another simulation (see Examples 2 and 3). The definitions in print or probe output statements can only be used in output statements. They cannot be referred by any other definitions.You can use the E-element: e1 in 0 vol='5*cos(6.28*v(10)*v(5)*k/360)' 326 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 11: Simulation Output Reusing Simulation Output as Input Stimuli (HSPICE Only) Then, the node 'in' can be used as the input to the other element in the same netlist, as shown in this example: M1 dr in src subr pch w=2u l=1u .subckt inv vdd 0 A B M1 A B vdd vdd pch w=6u M2 A B 0 0 nch w=3u .ends inv x1 vdd 0 in out inv l=1u l=1u You can use .STIM statements to save the signal from the first simulation in order to create a PWL source. .stim tran pwl filename=test1 vsrc[0]=v(in) node1=A node2=B from=0.0ns to=10ns + npoints=100 .stim tran pwl filename=test2 vsrc[1]=v(in) node1=C node2=D from=0.0ns to=10ns + npoints=50 In this example, the .STIM command creates two stimulus files named test1.pwl0_tr0 and test2.pwl2_tr0. Each has a voltage source: one namedvsrc[0], applied between nodes A and B, and one named vsrc[1], applied between nodes C and D. The stimulus files have a PWL source function based on the voltage of node 'in' during the time 0.0ns to 10ns with 50 points (for vsrc[0]) and 100 points (for vsrc[1]). Contents of the test1.pwl0_tr0 file: vsrc[0] A B PWL + 0. 5.0000 + 200.00000p 2.2114 + 400.00000p 2.4666 + 600.00000p -362.1421m ......................... Contents of the test2.pwl1_tr0 file: vsrc[1] C D PWL + 0. 5.0000 + 100.00000p -1.8008 + 200.00000p -3.2748 + 300.00000p -1.3264 ......................... The PWL files generated from the .STIM commands can be used as inputs to another simulation. HSPICE® User Guide: Simulation and Analysis B-2008.09 327 Chapter 11: Simulation Output Reusing Simulation Output as Input Stimuli (HSPICE Only) Load the signal in CosmosScope and then export the (x,y) data of the signal in text format by selecting File > Save > Plotfiles. You will have to edit the data so it looks like a PWL source by adding a source definition and line continuation characters. Output Files The .STIM statement generates the following output files: Output File Type Extension PWL Source .pwl\$_tr#The .STIM statement writes PWL source results to output_file.pwl\$_tr#. This output file results from a .STIM <tran> pwl statement in the input file. Data Card .dat\$_tr#, .dat\$_ac#, or .dat\$_sw#The .STIM statement writes DATA Card results to output_file.dat\$_sw#, output_file.dat\$_ac#, or output_file.dat\$_tr#. This output file is the result of a .stim <tran| ac|dc> data statement in the input file. Digital Vector File .vec\$_tr#The .STIM statement writes Digital Vector File results to output_file.vec\$_tr#. This output file is the result of a .stim <tran> vec statement in the input file. Symbol Description tr | ac | sw ■ ■ ■ tr=transient analysis. ac=AC analysis. sw=DC sweep analysis. # Either a sweep number, or a hard-copy file number. For a single sweep run, the default number is 0. \$ Serial number of the current .STIM statement, within statements of the same stimulus type (pwl, data, or vec). \$=0 ~ n-1 (n is the number of the .STIM statement of that type). The initial \$ value is 0. For example, if you specify three .STIM pwl statements, HSPICE generates three PWL output files, with the suffix names pwl0_tr#, pwl1_tr#, and pwl2_tr#. 328 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 11: Simulation Output Element Template Listings (HSPICE Only) Element Template Listings (HSPICE Only) A full and extensive listing of MOSFET output templates, is found in the HSPICE Reference Manual: MOSFET Models, MOSFET Output Templates. Table 25 Resistor (R Element) Name Alias Description G LV1 Conductance at analysis temperature. R LV2 Resistance at analysis temperature. TC1 LV3 First temperature coefficient. TC2 LV4 Second temperature coefficient. Table 26 Capacitor (C Element) Name Alias Description CEFF LV1 Computed effective capacitance. IC LV2 Initial condition. Q LX0 Charge, stored in capacitor. CURR LX1 Current, flowing through capacitor. VOLT LX2 Voltage, across capacitor. Table 27 Inductor (L Element) Name Alias Description LEFF LV1 Computed effective inductance. IC LV2 Initial condition. FLUX LX0 Flux, in the inductor. VOLT LX1 Voltage, across inductor. HSPICE® User Guide: Simulation and Analysis B-2008.09 329 Chapter 11: Simulation Output Element Template Listings (HSPICE Only) Table 27 Inductor (L Element) (Continued) Name Alias Description CURR LX2 Current, flowing through inductor. Table 28 Mutual Inductor (K Element) Name Alias Description K LV1 Mutual inductance. Table 29 Voltage-Controlled Current Source (G Element) Name Alias Description CURR LX0 Current, through the source, if VCCS. R LX0 Resistance value, if VCR. C LX0 Capacitance value, if VCCAP. CV LX1 Controlling voltage. CQ LX1 Capacitance charge, if VCCAP. DI LX2 Derivative of the source current, relative to the control voltage. ICAP LX2 Capacitance current, if VCCAP. VCAP LX3 Voltage, across capacitance, if VCCAP. Table 30 Voltage-Controlled Voltage Source (E Element) Name Description VOLT LX0 Source voltage. CURR LX1 Current, through source. CV 330 Alias LX2 Controlling voltage. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 11: Simulation Output Element Template Listings (HSPICE Only) Table 30 Voltage-Controlled Voltage Source (E Element) (Continued) Name Alias Description DV LX3 Derivative of the source voltage, relative to the control current. Table 31 Current-Controlled Current Source (F Element) Name Alias Description CURR LX0 Current, through source. CI LX1 Controlling current. DI LX2 Derivative of the source current, relative to the control current. Table 32 Current-Controlled Voltage Source (H Element) Name Alias Description VOLT LX0 Source voltage. CURR LX1 Source current. CI LX2 Controlling current. DV LX3 Derivative of the source voltage, relative to the control current. Table 33 Independent Voltage Source (V Element) Name Alias Description VOLT LV1 DC/transient voltage. VOLTM LV2 AC voltage magnitude. VOLTP LV3 AC voltage phase. HSPICE® User Guide: Simulation and Analysis B-2008.09 331 Chapter 11: Simulation Output Element Template Listings (HSPICE Only) Table 34 Independent Current Source (I Element) Name Alias Description CURR LV1 DC/transient current. CURRM LV2 AC current magnitude. CURRP LV3 AC current phase. Table 35 Diode (D Element) Name Alias Description AREA LV1 Diode area factor. AREAX LV23 Area, after scaling. IC LV2 Initial voltage, across diode. VD LX0 Voltage, across diode (VD), excluding RS (series resistance). IDC LX1 DC current, through diode (ID), excluding RS. Total diode current is the sum of IDC and ICAP. GD LX2 Equivalent conductance (GD). QD LX3 Charge of diode capacitor (QD). ICAP LX4 Current, through the diode capacitor. Total diode current is the sum of IDC and ICAP. C LX5 Total diode capacitance. PID LX7 Photo current, in diode. Table 36 BJT (Q Element) Name Description AREA 332 Alias LV1 Area factor. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 11: Simulation Output Element Template Listings (HSPICE Only) Table 36 BJT (Q Element) (Continued) Name Alias Description ICVBE LV2 Initial condition for base-emitter voltage (VBE). ICVCE LV3 Initial condition for collector-emitter voltage (VCE). MULT LV4 Number of multiple BJTs. FT LV5 FT (Unity gain bandwidth). ISUB LV6 Substrate current. GSUB LV7 Substrate conductance. LOGIC LV8 LOG 10 (IC). LOGIB LV9 LOG 10 (IB). BETA LV10 BETA. LOGBETAI LV11 LOG 10 (BETA) current. ICTOL LV12 Collector current tolerance. IBTOL LV13 Base current tolerance. RB LV14 Base resistance. GRE LV15 Emitter conductance, 1/RE. GRC LV16 Collector conductance, 1/RC. PIBC LV18 Photo current, base-collector. PIBE LV19 Photo current, base-emitter. VBE LX0 VBE. VBC LX1 Base-collector voltage (VBC). CCO LX2 Collector current (CCO). CBO LX3 Base current (CBO). HSPICE® User Guide: Simulation and Analysis B-2008.09 333 Chapter 11: Simulation Output Element Template Listings (HSPICE Only) Table 36 BJT (Q Element) (Continued) Name Alias Description GPI LX4 gπ=¹ib /¹vbe, constant vbc. GU LX5 gμ=¹ib /¹vbc, constant vbe. GM LX6 gm=¹ic /¹vbe+ ¹ic /¹vbe, constant vce. G0 LX7 g0=¹ic /¹vce, constant vbe. QBE LX8 Base-emitter charge (QBE). CQBE LX9 Base-emitter charge current (CQBE). QBC LX10 Base-collector charge (QBC). CQBC LX11 Base-collector charge current (CQBC). QCS LX12 Current-substrate charge (QCS). CQCS LX13 Current-substrate charge current (CQCS). QBX LX14 Base-internal base charge (QBX). CQBX LX15 Base-internal base charge current (CQBX). GXO LX16 1/Rbeff Internal conductance (GXO). CEXBC LX17 Base-collector equivalent current (CEXBC). CAP_BE LX19 cbe capacitance (Cπ). CAP_IBC LX20 cbc internal base-collector capacitance (Cμ). CAP_SCB LX21 csc substrate-collector capacitance for vertical transistors. csb substrate-base capacitance for lateral transistors. CAP_XBC cbcx external base-collector capacitance. CMCMO LX23 ¹(TF*IBE) /¹vbc. VSUB 334 LX22 LX24 Substrate voltage. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 11: Simulation Output Element Template Listings (HSPICE Only) Table 37 JFET (J Element) Name Alias Description AREA LV1 JFET area factor. VDS LV2 Initial condition for drain-source voltage. VGS LV3 Initial condition for gate-source voltage. PIGD LV16 Photo current, gate-drain in JFET. PIGS LV17 Photo current, gate-source in JFET. VGS LX0 VGS. VGD LX1 Gate-drain voltage (VGD). CGSO LX2 Gate-to-source (CGSO). CDO LX3 Drain current (CDO). CGDO LX4 Gate-to-drain current (CGDO). GMO LX5 Transconductance (GMO). GDSO LX6 Drain-source transconductance (GDSO). GGSO LX7 Gate-source transconductance (GGSO). GGDO LX8 Gate-drain transconductance (GGDO). QGS LX9 Gate-source charge (QGS). CQGS LX10 Gate-source charge current (CQGS). QGD LX11 Gate-drain charge (QGD). CQGD LX12 Gate-drain charge current (CQGD). CAP_GS LX13 Gate-source capacitance. CAP_GD LX14 Gate-drain capacitance. QDS LX16 Drain-source charge (QDS). HSPICE® User Guide: Simulation and Analysis B-2008.09 335 Chapter 11: Simulation Output Redirecting the Simulation Output Results Files to a Different Directory Table 37 JFET (J Element) (Continued) Name Alias Description CQDS LX17 Drain-source charge current (CQDS). GMBS LX18 Drain-body (backgate) transconductance (GMBS). Table 38 Saturable Core Element (K Element) Name Alias Description MU LX0 Dynamic permeability (mu), Weber/(amp-turn-meter). H LX1 Magnetizing force (H), Ampere-turns/meter. B LX2 Magnetic flux density (B), Webers/meter2. Table 39 Saturable Core Winding Name Alias Description LEFF LV1 Effective winding inductance (Henry). IC LV2 Initial condition. FLUX LX0 Flux, through winding (Weber-turn). VOLT LX1 Voltage, across winding (Volt). Redirecting the Simulation Output Results Files to a Different Directory If you need to I redirect the simulation output result files to a directory other than the current working directory., use either of the following two options. At a a command line prompt, enter either: % hspice -i test.sp -o /root/user/hspice/result/test.lis HSPICE redirects the simulation results to the specified location “/root/user/ hspice/result”. or 336 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 11: Simulation Output Using the HSPICE Output Converter Utility % hspice -i test.sp -o results/test.lis In the second example, HSPICE redirects the simulation results to the specified folder with respect to the current working directory. However, the destination folder should be created before starting the simulation. Otherwise, HSPICE returns an error message and aborts. Using the HSPICE Output Converter Utility This section describes how to convert output generated by HSPICE. The converter utility is a post-process tool used to convert the output files (*.tr#, *.ac#, and *.sw#) generated by HSPICE. You can use converter to get the Parameter Storage Format (PSF) output files directly from the .tr#, .ac#, or .sw# files generated by HSPICE with the POST output control option. You can also use the converter to get the PWL Source, DATA Card, and Digital Vector File (VEC) from the *.tr#, *.ac#, and *.sw# files generated by HSPICE with the POST or CSDF control options. You can reuse these stimuli in a new simulation. Note: The converter utility is not supported in HSPICE RF. Converter Features The converter utility converts *.tr#, *.ac#, and *.sw# files to PSF and PWL/ DATA/VEC files, which are described in the following sections. PSF Converter The PSF Converter runs on the following platforms: ■ Sun/Solaris 2.5 and 2.8 ■ HP/UX10.20 and 11.0 ■ IBM AIX5.1 HSPICE® User Guide: Simulation and Analysis B-2008.09 337 Chapter 11: Simulation Output Using the HSPICE Output Converter Utility Syntax converter -t PSF -i input_file <-o output_file> <-a/-b> Table 40 PSV Converter Parameters Argument Description -t Specifies the file type (must be psf). -i Specifies input file name. The input file must be the output file generated by HSPICE with the POST output control option. -o Specifies output file name. The converter assigns a .psf as the extension of the output file. If you do not specify the output file name, the converter appends _psf to the root name of the input file, and it remains the extension of the input file. -a Specifies the ASCII format for the output file. -b Specifies the binary format for the output file. By default, the output file is in binary format. The content included in angled brackets (< >) is optional. Example converter -t PSF -i testpost.tr0 -o testpsf The input file is testpost.tr0, which HSPICE generates with the POST option. The output file name is testpsf. After running, HSPICE generates two new files: testpsf.psf and logFile. The testpsf.psf file is a PSF file that you can view with the Analog Waveform Display (AWD). The logFile is necessary for the AWD to load the waveform. PWL/DATA/VEC Converter The PWL/DATA/VEC Converter runs on the following platforms: ■ ■ HP/UX10.20 and 11.0 ■ IBM AIX5.1 ■ 338 Sun/Solaris 2.5 and 2.8 DEC Alpha HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 11: Simulation Output Using the HSPICE Output Converter Utility ■ PC Linux/RedHat 6.2, 7.0, 7.1 and 7.2 ■ PC Windows NT4.0, 2000, and XP-Professional The PWL/DATA/VEC Converter is mainly for reusing previous simulation results directly from the *.tr#, *.ac#, and *.sw# files produced by HSPICE. The converter is in accordance with the .STIM statement in the HSPICE netlist. Syntax converter -t PWL/DATA/VEC -i input_file <-o output_file> Table 41 PWL/DATA/VEC Converter Parameters Argument Description -t Specifies the type of the stimulus (PWL). -i Specifies the input file name. The input file are the output files generated by HSPICE with the POST=x or CSDF=x output control options. -o Specifies the output file name. If you do not specify the output file name, the converter automatically assigns the following file names: ■ input_filename.tr#_PWL# input_filename.ac#_DAT# ■ input_filename.tr#_DAT# ■ input_filename.sw#_DAT# ■ input_filename.tr#_VEC# The content included by angled brackets (< >) is optional. ■ Note: For PWL and VEC, the input file must be generated by transient analysis. Prompt User Mode The PWL/DATA/VEC Converter is a prompt user mode. The converter displays corresponding prompts and asks you to input some data after you start it successfully. Input the following at the command line and press the Enter key: Converter -t PWL -i sample.tr0 The following input prompts appear one at a time and require your specified entries on the command line. 1. Enter the number of output variables(>0): HSPICE® User Guide: Simulation and Analysis B-2008.09 339 Chapter 11: Simulation Output Using the HSPICE Output Converter Utility Specify the number of output variables from the waveform file to be converted. 2. Enter output variables reused: Specify the name of the node(s) in the design to be converted. The node names must match a node name in the waveform file that you are converting. 3. Enter name of the source (optional): If no source is specified, the source name will be vm<node_name>. 4. Enter positive node name (optional): If no positive node is specified, the positive node name will be the same as node name(s) specified for the output variable(s). 5. Enter negative node name (optional): If no negative node is specified, 0 (ground) will be used as the negative node for each node name specified. 6. Enter independent variable type [1--from/to, 2-dispersed]: This input line is optional. If nothing is entered and you press the Enter key, the input prompts end, the executable automatically runs and generates the <design_name>.tr0_PWL0 stimuli file that will contain all time points from the original waveform file. If an independent variable type is specified, the following prompts are shown according to the type. A value is required for each prompt. 7. For 1-- from/to, Enter the start point: Starting point of the output file. 8. Enter the end point: Ending point of the output file. 9. Enter the number of output points: Number of output points. 10. For 2-- :dispersed Enter the dispersed points: Enter a list of time points that will be written to the file. 340 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 11: Simulation Output Using the HSPICE Output Converter Utility Once you enter the necessary information at the last prompt and press the Return key, the executable automatically runs and generates the design_name.tr0_PWL0 stimuli files. Input Line Dependencies The input lines you use must adhere to the following conditions: ■ Variables used in a PWL source must be voltage or current signals. ■ Variables used in a VEC file can only be voltage signals. ■ PWL Source Names must begin with V or I. ■ Dispersed time points must be increasing in value when the stimulus type is PWL or VEC. ■ For the optional items, you can enter the Return Key directly to adopt the default value. Running the Converter Utility in Batch Mode While the converter is interactive, prompting you with a series of questions, it can be run in batch mode by redirecting input from an “answer” file. The command to run the converter in batch mode has two parts and requires two files. The first file (see the following batch file), invokes the converter and tells it the waveform file to use. The second file is the “answer file” containing the answers to the conversion questions. The questions asked by the converter utility are listed in the section titled Prompt User Mode. You can create sample batch files using the following syntax: converter -t pwl -i file1.tr0 < answers1.txt converter -t pwl -i file2.tr0 < answers2.txt where, file1.tr0 and file2.tr0 are HSPICE generated transient output files. The above will create file1.tr0_PWL0 and file2.tr0_PWL0. Examples of input files with answers: HSPICE® User Guide: Simulation and Analysis B-2008.09 341 Chapter 11: Simulation Output Troubleshooting Issues // // // // single PWL created : 1 // # of signals v(nd) // names of signals vsig1 // name of PWL source sig1 // + node of PWL 0 // - node of PWL 1 // choose 1 for from/to , 2 to define each point 0 // start time 600p // end time 100 // # of points Answer file to create multiple PWL signals in one tr0_PWL0 file after first answer, an answer is needed for each signal even if they are the same 2 v(sig1) v(sig2) vsig1 vsig2 n1 n2 00 11 00 100n 100n 100 100 Troubleshooting Issues Resolving Inductor/Voltage Source Loop Errors HSPICE issues an inductor/voltage source loop error when: ■ Two or more voltage sources are connected to the same nodes. ■ A voltage source with an inductor is connected directly across its nodes. ■ Two or more inductors are connected in a loop and the current is not limited. The use of these topologies should be avoided. However, if HSPICE reports this error, then follow these steps to correct the error: 1. Find out where the topology exists and correct it. 2. Combine multiple voltage sources into a single equivalent voltage source. 3. Limit the current by connecting a small series resistance (1n ohm or smaller) to the voltage source loop. 342 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 11: Simulation Output Troubleshooting Issues Voltage Source Missing Rising and Falling Edges If you have defined rise and fall times in an independent voltage source, and the rise and fall times are missing when you look at the waveform of the source. The source is defined as: V1 in 0 pulse 0 5 10n 1n 1n 200n 333n .option post=2 See check.jpg for the resulting waveform. Figure 33 When you set .option POST=2, HSPICE prints the waveform file as ASCII data. When used with the default post-processing output version, POST_VERSION=9601, the number of significant digits is limited. This can cause a loss of resolution in the waveforms. If you set .option POST_VERSION=2001 in addition to .option POST=2, then the ASCII waveform data will contain more significant digits and the resolution will be increased and the rising and falling edges will be present (see check1.jpg). HSPICE® User Guide: Simulation and Analysis B-2008.09 343 Chapter 11: Simulation Output Troubleshooting Issues Figure 34 Using POST_VERSION=2001 will also cause the output file header to display the correct number of output variables when the number of output variables exceeds 9999. 344 HSPICE® User Guide: Simulation and Analysis B-2008.09 Part: 3 Analyses This Part contains the following chapters/topics: ■ Chapter 12, Initializing DC/Operating Point Analysis ■ Chapter 13, Pole/Zero Analysis ■ Chapter 14, Transient Analysis ■ Chapter 15, Spectrum Analysis ■ Chapter 16, AC Small-Signal and Noise Analysis ■ Chapter 17, Linear Network Parameter Analysis ■ Chapter 18, Statistical Eye Analysis ■ Chapter 19, Timing Analysis Using Bisection ■ Chapter 20, Analyzing Variability and Using the Variation Block ■ Chapter 21, Monte Carlo Analysis Using the Variation Block Flow ■ Chapter 22, Mismatch Analyses ■ Chapter 23, Exploration Block ■ Chapter 24, Optimization ■ Chapter 25, RC Reduction and Post-Layout Simulation ■ Chapter 26, MOSFET Model Reliability Analysis (MOSRA) HSPICE® User Guide: Simulation and Analysis B-2008.09 345 346 HSPICE® User Guide: Simulation and Analysis B-2008.09 12 Initializing DC/Operating Point Analysis 12 Describes DC initialization and operating point analysis. For descriptions of individual HSPICE commands referenced in this chapter, see the HSPICE Reference Manual: Commands and Control Options. These topics are covered in the following sections: ■ Simulation Flow—Initialization and Analysis ■ DC Initialization and Operating Point Calculation ■ .DC Statement—DC Sweeps ■ Other DC Analysis Statements ■ Accuracy and Convergence ■ Reducing DC Errors ■ Diagnosing Convergence Problems Simulation Flow—Initialization and Analysis Before it performs .OP, .DC sweep, .AC, or .TRAN analyses, HSPICE first sets the DC operating point values for all nodes and sources. To do this, HSPICE does one of the following: ■ Calculates all values ■ Applies values specified in .NODESET and .IC statements ■ Applies values stored in an initial conditions file. The .OPTION OFF statement, and the OFF and IC=val element parameters, also control initialization. HSPICE® User Guide: Simulation and Analysis B-2008.09 347 Chapter 12: Initializing DC/Operating Point Analysis Simulation Flow—Initialization and Analysis Initialization is fundamental to simulation. HSPICE starts any analysis with known nodal voltages (or initial estimates for unknown voltages) and some branch currents. It then iteratively finds the exact solution. Initial estimates that are close to the exact solution increase the likelihood of a convergent solution and a lower simulation time. A transient analysis first calculates a DC operating point using the DC equivalent model of the circuit (unless you specify the UIC parameter in the .TRAN statement). HSPICE then uses the resulting DC operating point as an initial estimate to solve the next timepoint in the transient analysis. The following describes how this is done: 1. If you do not provide an initial guess or if you provide only partial information, HSPICE provides a default estimate for each node in the circuit. 2. HSPICE then uses this estimate to iteratively find the exact solution. The .NODESET and .IC statements supply an initial guess for the exact DC solution of nodes within a circuit. 3. To set the seed value for the iterative dc algorithm for any circuit node to any value, use the .NODESET statement. 4. HSPICE then connects a voltage source equivalent, to each initialized node (a current source, with a GMAX parallel conductance, set with a .OPTION statement). 5. HSPICE next calculates a DC operating point, with the .NODESET voltage source equivalent connected. 6. HSPICE disconnects the equivalent voltage sources, which you set in the .NODESET statement, and recalculates the DC operating point. This is the DC operating point solution. I=GMAX*V Figure 35 348 GMAX To Initialization Node Equivalent Voltage Source: NODESET and .IC HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 12: Initializing DC/Operating Point Analysis Simulation Flow—Initialization and Analysis The .IC statement provides both an initial guess and a solution for selected nodes within the circuit. Nodes that you initialize with the .IC statement become part of the solution of the DC operating point. .IC and .NODESET statements can be used in a .DC analysis, in addition to .TRAN statements, unless .OPTION DCIC=0 is set. You can also use the OFF option to initialize active devices. The OFF option works with .IC and .NODESET voltages as follows: 1. If the netlist includes any .IC or .NODESET statements, HSPICE sets node voltages, according to those statements. 2. If you set the OFF option, HSPICE sets values to zero for the terminal voltages of all active devices (BJTs, diodes, MOSFETs, JFETs, MESFETs) that are not set in .IC or .NODESET statements, or by sources. 3. If element statements specify any IC parameters, HSPICE sets those initial conditions. 4. HSPICE uses the resulting voltage settings, as the initial guess at the operating point. Use OFF to find an exact solution, during an operating point analysis, in a large circuit. The majority of device terminals are at zero volts for the operating point solution. To initialize the terminal voltages to zero for selected active devices, set the OFF parameter in the element statements for those devices. After HSPICE finds a DC operating point, use .SAVE to store operatingpoint node voltages in a <design>.ic file. Then use the .LOAD statement to restore operating-point values from the *.ic file for later analyses. When you set initial conditions for Transient Analysis: ■ If you include UIC in a .TRAN statement, HSPICE starts a transient analysis, using node voltages specified in an .IC statement. ■ Use the .OP statement, to store an estimate of the DC operating point, during a transient analysis. ■ An internal timestep too small error message indicates that the circuit failed to converge. The cause of the failure can be that HSPICE cannot use stated initial conditions to calculate the actual DC operating point. Figure 36 shows the simulation flow for DC analysis in HSPICE. HSPICE® User Guide: Simulation and Analysis B-2008.09 349 Chapter 12: Initializing DC/Operating Point Analysis DC Initialization and Operating Point Calculation Simulation Experiment Transient DC Operating point Sweep analysis simulation AC DC-related AC small-signal analysis .DCMATCH .PZ .OPTION: Tolerance ABSI (ABSTOL) ABSMOS ABSV ABSVDC KCLTEST RELI RELMOS RELV RELVDC Figure 36 Matrix ITL1 NOPIV PIVOT PIVREF PIVREL PIVTOL SPARSE NOTOP Monte Carlo analysis .SENS .TF Convergence CONVERGE CSHDC DCFOR DCHOLD DCON DCSTEP DCTRAN DV GMAX GMINDC GRAMP GSHUNT ICSWEEP NEWTOL OFF Limit RESMIN DC Initialization and Operating Point Analysis Simulation Flow DC Initialization and Operating Point Calculation Use a .OP statement in HSPICE to: ■ Calculate the DC operating point of a circuit ■ Produce an operating point during a transient analysis A simulation can only have one .OP statement. 350 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 12: Initializing DC/Operating Point Analysis DC Initialization and Operating Point Calculation .OP Statement — Operating Point When you include an .OP statement in an input file, HSPICE calculates the DC operating point of the circuit. You can also use the .OP statement to produce an operating point, during a transient analysis. If an analysis requires calculating an operating point, you do not need to specify the .OP statement; HSPICE calculates an operating point. If you use a .OP statement, and if you include the UIC keyword in a .TRAN analysis statement, then simulation omits the time=0 operating point analysis, and issues a warning in the output listing. HSPICE® User Guide: Simulation and Analysis B-2008.09 351 Chapter 12: Initializing DC/Operating Point Analysis DC Initialization and Operating Point Calculation Output ***** OPERATING POINT INFORMATION TNOM=25.000 TEMP=25.000 ***** OPERATING POINT STATUS IS ALL SIMULATION TIME IS 0. NODE VOLTAGE NODE VOLTAGE NODE VOLTAGE + 0:2=0 0:3=437.3258M 0:4=455.1343M + 0:5=478.6763M 0:6=496.4858M 0:7=537.8452M + 0:8=555.6659M 0:10=5.0000 0:11=234.3306M **** VOLTAGE SOURCES SUBCKT ELEMENT 0:VNCE 0:VN7 0:VPCE 0:VP7 VOLTS 0 5.00000 0 -5.00000 AMPS -2.07407U -405.41294P 2.07407U 405.41294P POWER 0. 2.02706N 0. 2.02706N TOTAL VOLTAGE SOURCE POWER DISSIPATION=4.0541 N WATTS **** BIPOLAR JUNCTION TRANSISTORS SUBCKT ELEMENT 0:QN1 0:QN2 0:QN3 0:QN4 * Note: HSPICE RF does not support qn(element) * charge output. MODEL 0:N1 0:N1 0:N1 0:N1 IB 999.99912N 2.00000U 5.00000U 10.00000U IC -987.65345N -1.97530U -4.93827U -9.87654U VBE 437.32588M 455.13437M 478.67632M 496.48580M VCE 437.32588M 17.80849M 23.54195M 17.80948M VBC 437.32588M 455.13437M 478.67632M 496.48580M VS 0. 0. 0. 0. POWER 5.39908N 875.09107N 2.27712U 4.78896U BETAD -987.65432M -987.65432M -987.65432M -987.65432M GM 0. 0. 0. 0. RPI 2.0810E+06 1.0405E+06 416.20796K 208.10396K RX 250.00000M 250.00000M 250.00000M 250.00000M RO 2.0810E+06 1.0405E+06 416.20796K 208.10396K CPI 1.43092N 1.44033N 1.45279N 1.46225N CMU 954.16927P 960.66843P 969.64689P 977.06866P CCS 800.00000P 800.00000P 800.00000P 800.00000P BETAAC 0. 0. 0. 0. FT 0. 0. 0. 0. Element Statement IC Parameter Use the element statement parameter, IC=<val>, to set DC terminal voltages for selected active devices. HSPICE uses the value, set in IC=<val>, as the DC operating point value. 352 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 12: Initializing DC/Operating Point Analysis DC Initialization and Operating Point Calculation Example This example describes an H element dependent-voltage source: HXCC 13 20 VIN1 VIN2 IC=0.5, 1.3 The current, through VIN1, initializes to 0.5 mA. The current, through VIN2, initializes to 1.3 mA. Initial Conditions and UIC Parameters Use the .IC (or .DCVOLT), the IC parameter on an element statement, and the .NODESET commands to set transient initial conditions in HSPICE. How it initializes depends on whether the .TRAN analysis statement includes the UIC parameter. If you do not specify the UIC parameter in the .TRAN statement, HSPICE computes the DC operating point solution before the transient analysis. The node voltages that you specify in the .IC statement are fixed to determine the DC operating point. The node voltages that you specify in the .NODESET statement are used only in the first iteration to set an initial guess for the DC operating point analysis. Transient analysis releases the initialized nodes to calculate the second and later time points. If you specify the UIC parameter in the .TRAN statement, HSPICE does not calculate the initial DC operating point, but directly enters transient analysis. When you use .TRAN with UIC, the .TRAN node values (at time zero) are determined by searching for the first value found in this order: from .IC value, then IC parameter on an element statement, then .NODESET value, otherwise use a voltage of zero. Note that forcing a node value of the dc operating point may not satisfy KVL and KCL. In this event you may likely see activity during the initial part of the simulation. This may happen if UIC is used and some node values left unspecified, when too many (conflicting) .IC values are specified, or when node values are forced and the topology changes. In this event you may likely see activity during the initial part of the simulation. Forcing a node voltage applies a fixed equivalent voltage source during DC analysis and transient analysis removes the voltage sources to calculate the second and later time points. Therefore to correct DC convergence problems use .NODESET commands (without .TRAN with UIC) liberally (when a good guess can be provided) and use .ICs sparingly (when the exact node voltage is known). HSPICE® User Guide: Simulation and Analysis B-2008.09 353 Chapter 12: Initializing DC/Operating Point Analysis .DC Statement—DC Sweeps .SAVE and .LOAD Statements HSPICE saves the operating point, unless you use the .SAVE LEVEL=NONE statement. HSPICE restores the saved operating-point file, only if the input file contains a .LOAD statement. The .SAVE statement in HSPICE stores the operating point of a circuit, in a file that you specify. You can save the operating point data as either an .IC or a .NODESET statement. For quick DC convergence in subsequent simulations, use the .LOAD statement to input the contents of this file. HSPICE saves the operating point by default, even if the HSPICE input file does not contain a .SAVE statement. To not save the operating point, specify .SAVE LEVEL=NONE. A parameter or temperature sweep saves only the first operating point. If any node initialization commands, such as .NODESET and .IC, appear in the netlist after the .LOAD command, then they overwrite the .LOAD initialization. If you use this feature to set particular states for multistate circuits (such as flipflops), you can still use the .SAVE command to speed up the DC convergence. .SAVE and .LOAD work even on changed circuit topologies. Adding or deleting nodes results in a new circuit topology. HSPICE initializes the new nodes, as if you did not save an operating point. HSPICE ignores references to deleted nodes, but initializes coincidental nodes to the values that you saved from the previous run. When you initialize nodes to voltages, HSPICE inserts Norton-equivalent circuits at each initialized node. The conductance value of a Norton-equivalent circuit is GMAX=100, which might be too large for some circuits. If using .SAVE and .LOAD does not speed up simulation, or causes simulation problems, use .OPTION GMAX=1e-12 to minimize the effect of Nortonequivalent circuits on matrix conductances. HSPICE still uses the initialized node voltages to initialize devices. Do not use the .LOAD command for concatenated netlist files. .DC Statement—DC Sweeps You can use the .DC statement in DC analysis to: ■ ■ 354 Sweep any parameter value. Sweep any source value. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 12: Initializing DC/Operating Point Analysis Other DC Analysis Statements ■ Sweep temperature range. ■ Perform a DC Monte Carlo (random sweep) analysis. ■ Perform a data-driven sweep. ■ Perform a DC circuit optimization for a data-driven sweep. ■ Perform a DC circuit optimization, using start and stop. ■ Perform a DC model characterization. The .DC statement format depends on the application that uses it. For syntax details, refer to the .DC command in the HSPICE Reference Manual: Commands and Control Options. Other DC Analysis Statements HSPICE also provides the following DC analysis statements. Each statement uses the DC-equivalent model of the circuit in its analysis. For .PZ, the equivalent circuit includes capacitors and inductors. Statement Description .DCMATCH A technique for computing the effects of local variations in device characteristics on the DC solution of a circuit. .PZ Performs pole/zero analysis. .SENS Obtains DC small-signal sensitivities of output variables for circuit parameters. .TF Calculates DC small-signal values for transfer functions (ratio of output variable, to input source). HSPICE includes DC control options, and DC initialization statements, to model resistive parasitics and initialize nodes. These statements enhance convergence properties and accuracy of simulation. This section describes how to perform DC-related, small-signal analysis. HSPICE® User Guide: Simulation and Analysis B-2008.09 355 Chapter 12: Initializing DC/Operating Point Analysis DC Initialization Control Options DC Initialization Control Options Use control options in a DC operating-point analysis, to control DC convergence properties and simulation algorithms. Many of these options also affect transient analysis because DC convergence is an integral part of transient convergence. Include the following options for both DC and transient convergence: ■ Absolute and relative voltages. ■ Current tolerances. ■ Matrix options. Use .OPTION statements to specify the following options, which control DC analysis: ABSTOL DV ITL2 PIVREL CAPTAB GDCPATH KCLTEST PIVTOL CSHDC GRAMP MAXAMP RESMIN DCCAP GSHDC NEWTOL SPARSE DCFOR GSHUNT NOPIV SYMB DCHOLD ICSWEEP OFF DCIC ITLPTRAN PIVOT DCSTEP ITL1 PIVREF DC and AC analysis also use some of these options. Many of these options also affect the transient analysis because DC convergence is an integral part of transient convergence. For a description of transient analysis, see Chapter 14, Transient Analysis. Accuracy and Convergence Convergence is the ability to solve a set of circuit equations, within specified tolerances, and within a specified number of iterations. In numerical circuit 356 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 12: Initializing DC/Operating Point Analysis Accuracy and Convergence simulation, a designer specifies a relative and absolute accuracy for the circuit solution. The simulator iteration algorithm then attempts to converge to a solution that is within these set tolerances. That is, if consecutive simulations achieve results within the specified accuracy tolerances, circuit simulation has converged. How quickly the simulator converges, is often a primary concern to a designer—especially for preliminary design trials. So designers willingly sacrifice some accuracy for simulations that converge quickly. Accuracy Tolerances HSPICE uses accuracy tolerances that you specify, to assure convergence. These tolerances determine when, and whether, to exit the convergence loop. For each iteration of the convergence loop HSPICE subtracts previouslycalculated values from the new solution and compares the result with the accuracy tolerances. If the difference between two consecutive iterations is within the specified accuracy tolerances, the circuit simulation has converged. | Vnk - Vnk-1 | <=accuracy tolerance ■ Vnk is the solution at the n timepoint for iteration k. ■ Vnk-1 is the solution at the n timepoint for iteration k - 1. As Table 42 shows, HSPICE defaults to specific absolute and relative values. You can change these tolerances, so that simulation time is not excessive, but accuracy is not compromised. Accuracy Control Options on page 359 describes the options in Table 42. Table 42 Absolute and Relative Accuracy Tolerances Type .OPTION Default Nodal Voltage Tolerances ABSVDC 50 μv RELVDC .001 HSPICE® User Guide: Simulation and Analysis B-2008.09 357 Chapter 12: Initializing DC/Operating Point Analysis Accuracy and Convergence Table 42 Absolute and Relative Accuracy Tolerances Type .OPTION Default Current Element Tolerances ABSI 1 nA RELI .01 ABSMOS 1 uA RELMOS .05 HSPICE compares nodal voltages and element currents to the values from the previous iteration. ■ If the absolute value of the difference is less than ABSVDC or ABSI, then the node or element has converged. ABSV and ABSI set the floor value, below which HSPICE ignores values. Values above the floor use RELVDC and RELI as relative tolerances. If the iteration-to-iteration absolute difference is less than these tolerances, then it is convergent. Note: ABSMOS and RELMOS are the tolerances for MOSFET drain currents. Accuracy settings directly affect the number of iterations before convergence. ■ If accuracy tolerances are tight, the circuit requires more time to converge. ■ If the accuracy setting is too loose, the resulting solution can be inaccurate and unstable. Table 43 shows an example of the relationship between the RELVDC value, and the number of iterations. Table 43 RELV vs. Accuracy and Simulation Time for 2 Bit Adder RELVDC Delay (ns) Period (ns) Fall time (ns) .001 540 31.746 14.336 1.2797 .005 434 31.202 14.366 1.2743 .01 358 Iteration 426 31.202 14.366 1.2724 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 12: Initializing DC/Operating Point Analysis Accuracy and Convergence Table 43 RELV vs. Accuracy and Simulation Time for 2 Bit Adder RELVDC Iteration Delay (ns) Period (ns) Fall time (ns) .02 413 31.202 14.365 1.3433 .05 386 31.203 14.365 1.3315 .1 365 31.203 14.363 1.3805 .2 354 31.203 14.363 1.3908 .3 354 31.203 14.363 1.3909 .4 341 31.202 14.363 1.3916 .4 344 31.202 14.362 1.3904 Accuracy Control Options The default control option settings are designed to maximize accuracy, without significantly degrading performance. For a description of these options and their settings, see Appendix D, Transient Simulation with RUNLVL=0. ABSH DCON RELH ABSI DCTRAN RELI ABSMOS DI RELMOS ABSVDC GMAX RELV CONVERGE GMINDC RELVDC Autoconverge Process If a circuit does not converge in the number of iterations that ITL1 specifies, HSPICE initiates an autoconvergence process. This process manipulates DCON, GRAMP, and GMINDC, and even CONVERGE in some cases. Figure 37 on page 362 shows the autoconverge process. HSPICE® User Guide: Simulation and Analysis B-2008.09 359 Chapter 12: Initializing DC/Operating Point Analysis Accuracy and Convergence Note: HSPICE uses autoconvergence in transient analysis, but it also uses autoconvergence in DC analysis if the Newton-Raphson (N-R) method fails. In the process flow shown in Figure 37 on page 362: ■ Setting .OPTION DCON=-1 disables steps 2 and 3. ■ Setting .OPTION CONVERGE=-1 disables steps 4 and 5. ■ Setting .OPTION DCON=-1 CONVERGE=-1 disables steps 2, 3, 4, and 5. ■ If you set the DV option to a value other than the default, step 2 uses the value you set for DV, but step 3 changes DV to 1e6. ■ Setting .OPTION GRAMP has no effect on autoconverge. Autoconverge sets GRAMP independently. ■ If you set .OPTION GMINDC, then GMINDC ramps to the value you set, instead of to 1e-12, in steps 2 and 3. DCON and GMINDC The GMINDC option helps stabilize the circuit, during DC operating-point analysis. For MOSFETs, GMINDC helps stabilize the device in the vicinity of the threshold region. HSPICE inserts GMINDC between: ■ Drain and bulk. ■ Source and bulk. ■ Drain and source. The drain-to-source GMINDC helps to: ■ Linearize the transition from cutoff to weakly-on. ■ Smooth-out model discontinuities. ■ Compensate for the effects of negative conductances. The pn junction insertion of GMINDC in junction diodes linearizes the low conductance region. As a result, the device behaves like a resistor in the lowconductance region. This prevents the occurrence of zero conductance, and improves the convergence of the circuit.If a circuit does not converge, HSPICE automatically sets the DCON option. This option invokes GMINDC ramping, in steps 2 and 3 of Figure 37 on page 362. GMINDC for various elements is shown in Figure 38 on page 363. 360 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 12: Initializing DC/Operating Point Analysis Accuracy and Convergence Start STEP 1 [Newton-Raphson method] Iterates up to the ITL1 limit. Iterate Y Results Converged? N STEP 2 [GMINDC ramping method] Sets DCON=1 Sets DV to 0.1 or 0.3 Sets GRAMP= (6 or the value user set through .option GRAMP=xx) Ramps GMINDC from GMINDC⋅ 10GRAMP to 1e-12. Try DCON=1 Converged? Y Results N STEP 3 [GMINDC ramping method] Relaxes DV to 1e6. Ramps GMINDC from the successful point in Step 3 to 1e-12. Try DCON=2 Converged? Y N Try CONVERGE=1 Converged? Y N Try CONVERGE=5 Results STEP 4 [Pseudo tran method] Resets GMINDC through .OPTION GMINDC=xx Adds CSHDC and GSHUNT from each node to ground. Ramps supplies from zero to the set values. Removes CSHDC and GSHUNT, after DC convergence. Also iterates to a stable DC-bias point. Results STEP 5 [GSHUNT ramping algorithm] Ramping the GSHUNT parameter from 1e-4 to 0 obtains the solution at every GSHUNT point by invoking Newton-Raphson, GMINDC ramping algorithms. Y Converged? Results N Try CONVERGE=4 Converged? Y STEP 6 [GMATH ramping method] Adds CSHDC from each node to ground. Ramps gmath=cshdc/delta in the range of 1.0e-12 to 10.0. Set gmath to zero, if convergence occurs with gmath under 1.0e-12, and iterates once more to a stable DC bias point. Results N Non-convergence report HSPICE® User Guide: Simulation and Analysis B-2008.09 361 Chapter 12: Initializing DC/Operating Point Analysis Accuracy and Convergence Figure 37 Autoconvergence Process Flow Diagram In the Auto Convergence Process Flow diagram (Figure 37 on page 362): ■ ■ Setting .OPTION CONVERGE=-1 disables Steps 4 and 5. ■ Setting .OPTION DCON=-1 CONVERGE=-1 disables Steps 2, 3, 4, and 5. ■ Setting the DV option to a value other than the default, Step 2 uses the value you set for DV, but Step 3 changes DV to 1e6. ■ Setting .OPTION GRAMP has no effect on autoconverge. Autoconverge sets GRAMP independently. ■ Setting .OPTION GMINDC, then GMINDC ramps to the value you set, instead of to 1e-12, in Steps 2 and 3. ■ Setting .OPTION CONVERGE=5 invokes GSHUNT ramping which is tried before GMATH ramping due to a more robust algorithm than GMATH. The GSHUNT algorithm provides enhancements to the autoconvergence flow current probe, and numerical stability. ■ 362 Setting .OPTION DCON=-1 disables Steps 2 and 3. Setting .OPTION CONVERGE=4 invokes the GMATH ramping method. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 12: Initializing DC/Operating Point Analysis Accuracy and Convergence GMINDC Diode element GMINDC BJT element GMINDC GMINDC MOSFET element GMINDC GMINDC JFET or MESFET element GMINDC Figure 38 GMINDC Insertion HSPICE® User Guide: Simulation and Analysis B-2008.09 363 Chapter 12: Initializing DC/Operating Point Analysis Reducing DC Errors Reducing DC Errors To reduce DC errors, perform the following steps: 1. To check topology, set .OPTION NODE, to list nodal cross-references. • Do all MOS p-channel substrates connect to either VCC or positive supplies? • Do all MOS n-channel substrates connect to either GND or negative supplies? • Do all vertical NPN substrates connect to either GND or negative supplies? • Do all lateral PNP substrates connect to negative supplies? • Do all latches have either an OFF transistor, a .NODESET, or an .IC, on one side? • Do all series capacitors have a parallel resistance, or is .OPTION DCSTEP set? 2. Verify your .MODEL statements. • Check all model parameter units. Use model printouts to verify actual values and units because HSPICE multiplies some model parameters by scaling options. • Are subthreshold parameters of MOS models at reasonable values? • Are JS and JSW set in the MOS model for the DC portion of a diode model? A typical JS value is 1e-4A/M2. • Are CJ and CJSW set in MOS diode models? • Is weak-inversion NG and ND set in JFET/MESFET models? • Make sure that DIODE models have non-zero values for saturation current, junction capacitance, and series resistance. • Use MOS ACM=1, ACM=2, or ACM=3 source and drain diode calculations to automatically generate parasitics. 3. General remarks: • 364 Ideal current sources require large values of .OPTION GRAMP, especially for BJT and MESFET circuits. Such circuits do not ramp up with the supply voltages, and can force reverse-bias conditions, leading to excessive nodal voltages. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 12: Initializing DC/Operating Point Analysis Reducing DC Errors • Schmitt triggers are unpredictable for DC sweep analysis, and sometimes for operating points for the same reasons that oscillators and flip-flops are unpredictable. Use slow transient. • Large circuits tend to have more convergence problems because they have a higher probability of uncovering a modeling problem. • Circuits that converge individually, but fail when combined, are almost guaranteed to have a modeling problem. • Open-loop op-amps have high gain, which can lead to difficulties in converging. Start op-amps in unity-gain configuration, and open them up in transient analysis, using a voltage-variable resistor, or a resistor with a large AC value (for AC analysis). 4. Check your options: • Remove all convergence-related options, and try first with no special .OPTION settings. • Check non-convergence diagnostic tables for non-convergent nodes. Look up non-convergent nodes in the circuit schematic. They are usually latches, Schmitt triggers, or oscillating nodes. • For stubborn convergence failures, bypass DC all together, and use .TRAN with UIC set. Continue transient analysis until transients settle out, then specify the .OP time, to obtain an operating point during the transient analysis. To specify an AC analysis during the transient analysis, add an .AC statement to the .OP time statement. • SCALE and SCALM scaling options have a significant effect on parameter values in both elements and models. Be careful with units. Shorted Element Nodes HSPICE disregards any capacitor, resistor, inductor, diode, BJT, or MOSFET if all of its leads connect together. The simulation ignores it in its component tally, and issues a warning: **warning** all nodes of element x:<name> are connected together Inserting Conductance, Using DCSTEP In a DC operating-point analysis, failure to include conductances in a capacitor model results in broken circuit loops (because a DC analysis opens all HSPICE® User Guide: Simulation and Analysis B-2008.09 365 Chapter 12: Initializing DC/Operating Point Analysis Reducing DC Errors capacitors). This might not be solvable. If you include a small conductance in the capacitor model, the circuit loops are complete, and HSPICE can solve them. Modeling capacitors as complete opens, can result in this error: No DC Path to Ground For a DC analysis, use .OPTION DCSTEP, to assign a conductance value to all capacitors in the circuit. DCSTEP calculates the value as: conductance=capacitance/DCSTEP In Figure 39 on page 366, HSPICE inserts conductance (G), in parallel with capacitance (Cg). This provides current paths around capacitances, in DC analysis. Cg original circuit Cg G after conductance insertion G G G Figure 39 G = Cg/DCSTEP Conductance Insertion Floating-Point Overflow If MOS conductance is negative or zero, HSPICE might have difficulty converging. An indication of this type of problem is a floating-point overflow, during matrix solutions. HSPICE detects floating-point overflow, and invokes the Damped Pseudo Transient algorithm (CONVERGE=1), to try to achieve DC 366 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 12: Initializing DC/Operating Point Analysis Diagnosing Convergence Problems convergence without requiring you to intervene. If GMINDC is 1.0e-12 or less when a floating-point overflows, HSPICE sets it to 1.0e-11. Diagnosing Convergence Problems Before simulation, HSPICE diagnoses potential convergence problems in the input circuit, and provides an early warning, to help you in debugging your circuit. If HSPICE detects a circuit condition that might cause convergence problems, it prints the following message into the output file: Warning: Zero diagonal value detected at node ( ) in equation solver, which might cause convergence problems. If your simulation fails, try adding a large resistor between node ( ) and ground. Non-Convergence Diagnostic Table If a circuit cannot converge, HSPICE automatically generates two printouts, called the diagnostic tables: ■ Nodal voltage printout: Prints the names of all no-convergent node voltages, and the associated voltage error tolerances (tol). ■ Element printout: Lists all non-convergent elements, and their associated element currents, element voltages, model parameters, and current error tolerances (tol). To locate the branch current or nodal voltage that causes non-convergence, use the following steps: 1. Analyze the diagnostic tables. Look for unusually large values of branch currents, nodal voltages or tolerances. 2. After you locate the cause, use the .NODESET or .IC statements, to initialize the node or branch. If circuit simulation does not converge, HSPICE automatically generates a non-convergence diagnostic table, indicating: • The quantity of recorded voltage failures. • The quantity of recorded branch element failures. Any node in a circuit can create voltage failures, including hidden nodes (such as extra nodes that parasitic resistors create). HSPICE® User Guide: Simulation and Analysis B-2008.09 367 Chapter 12: Initializing DC/Operating Point Analysis Diagnosing Convergence Problems 3. Check the element printout for the subcircuit, model, and element name for all parts of the circuit where node voltages or currents do not converge. For example, Table 44 on page 368 identifies the xinv21, xinv22, xinv23, and xinv24 inverters, as problem subcircuits in a ring oscillator. It also indicates that the p-channel transistors, in the xinv21, xinv22, xinv24 subcircuits, are nonconvergent elements. The n-channel transistor of xinv23 is also a nonconvergent element. The table lists voltages and currents for the transistors, so you can check whether they have reasonable values. The tolds, tolbd, and tolbs error tolerances indicate how close the element currents (drain to source, bulk to drain, and bulk to source) are, to a convergent solution. For tol variables, a value close to or below 1.0 is a convergent solution. In Table 44, the tol values that are around 100, indicate that the currents were far from convergence. The element current and voltage values are also shown (id, ibs, ibd, vgs, vds, and vbs). Examine whether these values are realistic, and determine the transistor regions of operation. Table 44 Subcircuit Voltage, Current, and Tolerance subckt element model xinv22 22:mphc1 0:p1 xinv23 23:mphc1 0:p1 xinv23 23:mnch1 0:n1 xinv24 24: mphc1 0:p1 id 27.5809f 140.5646u 1.8123p 1.7017m 5.5132u ibs 205.9804f 3.1881f 31.2989f 0. 200.0000f ibd 0. 0. 0. -168.7011f 0. vgs 4.9994 -4.9992 69.9223 4.9998 -67.8955 vds 4.9994 206.6633u 69.9225 -64.9225 2.0269 vbs 4.9994 206.6633u 69.9225 0. 2.0269 vth -653.8030m -745.5860m -732.8632m 549.4114m -656.5097m tolds 114.8609 82.5624 155.9508 104.5004 5.3653 tolbd 0. 0. 0. 0. 0. tolbs 368 xinv21 21:mphc1 0:p1 3.534e-19 107.1528m 0. 0. 0. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 12: Initializing DC/Operating Point Analysis Diagnosing Convergence Problems Traceback of Non-Convergence Source To locate a non-convergence source, trace the circuit path for error tolerance. For example, in an inverter chain, the last inverter can have a very high error tolerance. If this is the case, examine the error tolerance of the elements that drive the inverter. If the driving tolerance is high, the driving element could be the source of non-convergence. However, if the tolerance is low, check the driven element as the source of non-convergence. Examine the voltages and current levels of a non-convergent MOSFET to discover the operating region of the MOSFET. This information can flow to the location of the discontinuity in the model—for example, subthreshold-to-linear, or linear-to-saturation. When considering error tolerances, check the current and nodal voltage values. If these values are extremely low, a relatively large number is divided by a very small number. This produces a large calculation result, which can cause the non-convergence errors. To solve this, increase the value of the absoluteaccuracy options. Use the diagnostic table, with the DC iteration limit (ITL1 option), to find the sources of non-convergence. When you increase or decrease ITL1, HSPICE prints output for the problem nodes and elements for a new iteration—that is, the last iteration of the analysis that you set in ITL1. Solutions for Non-Convergent Circuits Non-convergent circuits generally result from: ■ Poor Initial Conditions ■ Inappropriate Model Parameters ■ PN Junctions (Diodes, MOSFETs, BJTs) The following sections explain these conditions. Poor Initial Conditions Multi-stable circuits need state information, to guide the DC solution. You must initialize ring oscillators and flip-flops. These multi-stable circuits can either produce an intermediate forbidden state, or cause a DC convergence problem. To initialize a circuit, use the .IC statement, which forces a node to the requested voltage. Ring oscillators usually require you to set only one stage. HSPICE® User Guide: Simulation and Analysis B-2008.09 369 Chapter 12: Initializing DC/Operating Point Analysis Diagnosing Convergence Problems .IC V(1)=5V 1 Figure 40 2 3 4 5 Ring Oscillator The best way to set up the flip-flop is to use an .IC statement in the subcircuit definition. Example The following example sets the local Qset parameter to 0, and uses this value for the .IC statement, to initialize the Q latch output node. As a result, all latches have a default state of Q low. Setting Qset to vdd calls a latch, which overrides this state. .subckt latch in Q Q/ d Qset=0 .ic Q=Qset ... .ends Xff data_in[1] out[1] out[1]/ strobe LATCH Qset=vdd Inappropriate Model Parameters If you impose non-physical model parameters, you might create a discontinuous IDS or capacitance model. This can cause an internal timestep too small error, during the transient simulation. The mosivcv.sp demonstration file shows IDS, VGS, GM, GDS, GMB, and CV plots for MOS devices. A sweep near threshold from Vth-0.5 V to Vth+0.5 V (using a delta of 0.01 V), sometimes discloses a possible discontinuity in the curves. 370 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 12: Initializing DC/Operating Point Analysis Diagnosing Convergence Problems Ids I-V characteristics exhibiting saturation conductance = zero Vds Ids I-V exhibiting VDSAT slope error Vds Ids I-V exhibiting negative resistance region Vds Figure 41 Discontinuous I-V Characteristics If simulation does not converge when you add a component or change a component value, then the model parameters are not appropriate or do not correspond to physical values they represent. To locate the problem, follow these steps: 1. Check the input netlist file for non-convergent elements. Devices with a TOL value greater than 1, are non-convergent. 2. Find the devices at the beginning of the combined-logic string of gates that seem to start the non-convergent string. HSPICE® User Guide: Simulation and Analysis B-2008.09 371 Chapter 12: Initializing DC/Operating Point Analysis Diagnosing Convergence Problems 3. Check the operating point of these devices very closely, to see what region they operate in. Model parameters associated with this region are probably inappropriate. Circuit simulation uses single-transistor characterization, to simulate a large collection of devices. If a circuit fails to converge, the cause can be a single transistor, anywhere in the circuit. PN Junctions (Diodes, MOSFETs, BJTs) PN junctions found in diode, BJT, and MOSFET models, might exhibit nonconvergent behavior, in both DC and transient analysis. Example PN junctions often have a high off resistance, resulting in an ill-conditioned matrix. To overcome this, use .OPTION GMINDC and .OPTION GMIN to automatically parallel every PN junction in a design, with a conductance. Non-convergence can occur if you overdrive the PN junction. This happens if you omit a current-limiting resistor, or if the resistor has a very small value. In transient analysis, protection diodes are often temporarily forward-biased (due to the inductive switching effect). This overdrives the diode, and can result in non-convergence, if you omit a current-limiting resistor. Troubleshooting DC Bias Point and DC Sweep Non-Convergence The following procedures are designed to trade runtime performance and loosen certain tolerance bounds to overcome DC non-convergence. HSPICE steps from one DC convergence algorithm to another other to find a solution. You can assist this process as follows (in the same order). 1. Remove or comment out all simulation control options from your HSPICE testbench/netlists to allow the default auto-convergence procedure to work. 2. For circuits with feedback or multiple bias states (FF and latches), it is important to provide HSPICE with an initial guess that is close to the final solution. Use the .NODESET command to set initial voltage guesses. In particular, focus on those nodes that are listed as nonconvergent in the output .lis file. .nodeset v(in)=0 v(out)=3.3 3. Use the symbolic (.OPTION SYMB) operating point algorithm which finds initial guesses before calculating the operating point. .option SYMB=1 372 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 12: Initializing DC/Operating Point Analysis Diagnosing Convergence Problems Explanation: When the SYMB option is used, HSPICE assumes the circuit is digital and assigns a low/high state to all nodes as a reasonable initial voltage guess. This option improves DC convergence for oscillators, logic, and mixed-signal circuits. 4. Increase ITL1 from default value of 200 up to 500 in steps of 100. To further help DC sweep analysis, you may increase ITL2 in the same manor which increases the number of iterations HSPICE will take at each DC sweep point. .option ITL1=300 ITL2=300 Explanation: If increasing ITL2 doesn't help DC sweep analysis, the problem likely lies in model discontinuities. In other words, if you set ITL2=400 and the convergence problem is not solved, it is unlikely that any further increase of the value of ITL2 will help convergence. As a workaround, you may try to increase and offset the sweep size in an attempt to miss model problems. Original: .dc vin 0v 3.3v .1v Increase: .dc vin 0v 3.3v .2v Offset: .dc vin .01v 3.31v .1v 5. HSPICE will try various convergence algorithms as it struggles to achieve DC convergence. Read the .lis file to see where HSPICE was when the job aborted. HSPICE first tries DCON=1,2, then converge=1. If this isn't enough, try the other two converge choices along with larger gmindc values (converge=3 is the source stepping method listed in “Inside SPICE”). However, gmindc should not be set larger than 1e-9. .option converge=2 gmindc=1e-11 .option converge=3 gmindc=1e-11 6. If certain active element nodes seem to be non-convergent, you may have HSPICE perform 2 DC bias point calculations. The first calculation is performed with the active elements turned off. Then, this solution is used as the first guess for the DC solution with the elements turned on. You may choose one or more elements to turn off, declared on the element line. Diode n1 n2 diode_model off Qbjt n1 n2 n3 bjt_model off Mosfet n1 n2 n3 n4 mos_model off HSPICE® User Guide: Simulation and Analysis B-2008.09 373 Chapter 12: Initializing DC/Operating Point Analysis Diagnosing Convergence Problems Convergence Failure: Too Many Current Probes in Netlist Probing current in HSPICE is accomplished by the insertion of a zero-volt source. When large numbers of current probes are added explicitly or use of wildcard syntax such as .probe i(*), the size of the solution matrix increases significantly which can lead to convergence failures. These failures are usually accompanied by the error message: **diagnostic** rebuilding matrix with pivot option for special current probe process which is then followed by **error** no convergence in operating point. Workarounds: ■ Reduce the number of current probes by only probing specific nodes of interest, or adding a qualification to the wildcard. ■ Create a saved operating point and tell HSPICE to use those initial conditions in the transient analysis. The basic steps are: ■ Run HSPICE without all the current probes, but include a .OP statement to create an initial conditions (.ic0) file. ■ Include that file in your netlist. Example: .include my_design.ic0 ■ Add “uic” for Use Initial Conditions on the .TRAN line. Example: .tran 1n 100n uic Then, it is possible that the design will run to completion even with the large number of current probes. For more information on non-convergence, refer to Autoconverge Process and Reducing DC Errors in this chapter. 374 HSPICE® User Guide: Simulation and Analysis B-2008.09 13 13 Pole/Zero Analysis Describes how to use pole/zero analysis in HSPICE or HSPICE RF. You can use pole/zero analysis in HSPICE or HSPICE RF to study the behavior of linear, time-invariant networks. You can apply the results to the design of analog circuits, such as amplifiers and filters. Use pole/zero analysis to determine the stability of a design, or to calculate the poles and zeroes to specify in a POLE function (see Using Pole/Zero Analysis on page 376). Pole/zero analysis uses the .PZ (Pole/Zero) statement, instead of pole/zero (POLE function) and Laplace (LAPLACE function) transfer function modeling, which are also described in Using Pole/Zero Analysis on page 376. Overview of Pole/Zero Analysis In pole/zero analysis, a network transfer function describes a network. For any linear time-invariant network, you can use this general form to write the function: a 0 s m + a 1 ⋅ s ( m – 1 ) + …+ a m N(s) H ( s ) = ----------- = --------------------------------------------------------------------D(s) b 0 s n + b 1 ⋅ s ( n – 1 ) + …+ b n In the factorized form, the general function is: a 0 ( s + z 1 ) ( s + z 2 )… s + z i )… s + z m ) ( ( H ( s ) = ---- ⋅ -----------------------------------------------------------------------------------b 0 ( s + p 1 ) ( s + p 2 )… s + p j )… s + p m ) ( ( HSPICE® User Guide: Simulation and Analysis B-2008.09 375 Chapter 13: Pole/Zero Analysis Using Pole/Zero Analysis ■ The roots of the numerator N(s) (that is, zi) are the zeros of the network function. ■ The roots of the denominator D(s) (that is, pj) are the poles of the network function. ■ S is a complex frequency. The dynamic behavior of the network depends on the location of the poles and zeros, on the network function curve (complex plane). The (real) poles are the natural frequencies of the network. You can graphically deduce the magnitude and phase curve of most network functions from the location of its poles and zeros (reference 2). References on page 394 lists a variety of source materials that address: ■ Transfer functions of physical systems. ■ Design of systems and physical modeling. ■ Interconnect transfer function modeling. Using Pole/Zero Analysis HSPICE RF uses the exact matrix approach and the Muller method, while HSPICE uses only the Muller method to calculate the roots of the N(s) and D(s) polynomials. Matrix Approach The matrix approach is based on the singular-value matrix decomposition algorithm. It applies primarily to a network that has no frequency-dependent elements. In this case, HSPICE RF writes the D(s) function as the determinant of the network matrices, D(s) = det(G + sC), where G is the frequencyindependent conductance matrix and C is the capacitance matrix. The poles can be the eigen values of the matrix equation (G + sC) X = 0, where X is the eigen vector. Similarly, following Cramer’s rule, the roots of the N(s) function can also be the eigen values of a matrix. HSPICE RF supports two different kinds of singular values deposition (svd): ■ ■ 376 OPTION=HQR requires that the G matrix is non-singular. OPTION=SVD requires only that G and C are real matrices. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 13: Pole/Zero Analysis Using Pole/Zero Analysis The later SVD requires twice as much memory as the first one, and is approximately three times slower. Muller Method You can apply the Muller method if the network contains frequency-dependent elements (such as S or W Elements). The Muller method approximates the polynomial, using a quadratic equation that fits through three points in the vicinity of a root. To obtain successive iterations toward a particular root, HSPICE or HSPICE RF finds the nearer root of a quadratic, whose curve passes through the last three points. In Muller’s method, selecting the three initial points affects both the convergence of the process, and the accuracy of the roots obtained: 1. If the poles or zeros occupy a wide frequency range, then choose (X0R, X0I) close to the origin, to find poles or zeros at the zero frequency first. 2. Find the remaining poles or zeros, in increasing order. The (X1R, X1I) and (X2R, X2I) values can be orders of magnitude larger than (X0R, X0I). If any poles or zeros occur at high frequencies, adjust X1I and X2I accordingly. Pole/zero analysis results are based on the circuit’s DC operating point, so the operating point solution must be accurate. Use the .NODESET statement (not .IC) for initialization, to avoid DC convergence problems. For the syntax of the .PZ statement, see the HSPICE Reference Manual: Commands and Control Options. How HSPICE Calculates Poles and Zeros HSPICE calculates poles and zeros independently from the denominator and numerator polynomials of the transfer function respectively. It is possible that there exist common multipliers, such as the pole and zero appearing at exactly the same location. In this case, the pole and zero will just factor out. HSPICE only presents the roots of the two polynomials without doing the factorization. For example, if you use the netlist fkerwin.sp from the demo folder, from the transfer function there should be two poles and zeros: * * * = (s**2 + 2) / (s**2 + 0.1*s + 1) poles --- (-0.05004,+0.9987) , (-0.05004,-0.9987) zeros --- ( 0.0 ,+1.4142) , ( 0.0 ,-1.4142) HSPICE® User Guide: Simulation and Analysis B-2008.09 377 Chapter 13: Pole/Zero Analysis Pole/Zero Analysis Examples But HSPICE reports three poles and zeros: poles (rad/sec) poles (hertz) *************************************************************** real imag real imag zeros (rad/sec) zeros (hertz) -50.0394m 998.7214m -7.9640m 158.9515m -50.0394m -998.7214m -7.9640m -158.9515m *************************************************************** real imag real imag 0. -1.4142 0. -225.0812m 0. 1.4142 0. 225.0812m -1.4142 0. -225.0812m 0. -1.4142 0. -225.0812m 0. The common pole and zero at -1.4142 0 is cancelled in the transfer function. Since HSPICE solves the denominator and numerator separately, these are reported in the results. Pole/Zero Analysis Examples The following are examples of different types of pole/zero analysis. Example 1 – Low-Pass Filter This example is based on HSPICE demonstration netlist flp5th.sp, which is available in directory \$<installdir>/demo/hspice/filters: 378 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 13: Pole/Zero Analysis Pole/Zero Analysis Examples file:flp5th.sp lowpass 5th order filter ***** * reference: gabor c. temes and sanjit k. mitra, "modern fiter theory * and design", j. wiley, 1973, page 74. * t = v(3) / iin * =0.113*(s**2 + 1.6543)*(s**2 + 0.2632) / * (s**5 + 0.9206*s**4 + 1.26123*s**3 + 0.74556*s**2 * + 0.2705*s + 0.09836) ***** * pole zero, ac(.001hz-10hz) analysis * .options post .pz v(3) iin .ac dec 100 .001hz 10hz .probe ac vdb(3) vp(3) * iin 1 0 1.00 ac 1 r1 1 0 1.0 c3 1 0 1.52 c4 2 0 1.50 c5 3 0 0.83 c1 1 2 0.93 l1 1 2 0.65 c2 2 3 3.80 l2 2 3 1.00 r2 3 0 1.0 .end The following is an equivalent example in HSPICE RF: * HSPICE RF example: 5TH-ORDER LOW_PASS FILTER * .OPTION POST .PZ I(R2) IN .AC DEC 100 .001HZ 10HZ IN 0 1 1.00 AC 1 R1 1 0 1.0 C3 1 0 1.52 C4 2 0 1.50 C5 3 0 0.83 C1 1 2 0.93 L1 1 2 0.65 C2 2 3 3.80 L2 2 3 1.00 R2 3 0 1.00 .END HSPICE® User Guide: Simulation and Analysis B-2008.09 379 Chapter 13: Pole/Zero Analysis Pole/Zero Analysis Examples C1=0.93 R1=1 Figure 42 C3=1.52 C2=3.8 L1=0.65 C4=1.5 L2=1 C5=0.83 R2=1 Low-Pass Prototype Filter Table 45 shows the magnitude and phase variation of the current output, resulting from AC analysis. These results are consistent with pole/zero analysis. The pole/zero unit is radians per second, or hertz. The X-axis unit, in the plot, is in hertz. Table 45 Pole/Zero Analysis Results for Low-Pass Filter Poles (rad/sec) Poles (Hertz) Real Imaginary Real Imaginary -6.948473e-02 -4.671778e-01 -1.105884e-02 -7.435365e-02 -6.948473e-02 4.671778e-01 -1.105884e-02 7.435365e-02 -1.182742e-01 -8.914907e-01 -1.882392e-02 -1.418852e-01 -1.182742e-01 8.914907e-01 -1.882392e-02 1.418852e-01 -5.450890e-01 0.000000e+00 -8.675361e-02 0.000000e+00 0.000000e+00 -1.286180e+00 0.000000e+00 -2.047019e-01 0.000000e+00 -5.129892e-01 0.000000e+00 -8.164476e-02 0.000000e+00 5.129892e-01 0.000000e+00 8.164476e-02 0.000000e+00 1.286180e+00 0.000000e+00 2.047019e-01 Constant Factor = 1.129524e-01 380 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 13: Pole/Zero Analysis Pole/Zero Analysis Examples Figure 43 Fifth-Order Low-Pass Filter Response Example 2 – Kerwin’s Circuit This example is a HSPICE input file for pole/zero analysis of Kerwin’s circuit, which is located in the following directory: \$installdir/demo/hspice/filters/fkerwin.sp Table 46 lists analysis results. HSPICE® User Guide: Simulation and Analysis B-2008.09 381 Chapter 13: Pole/Zero Analysis Pole/Zero Analysis Examples R3=1/2 C1=0.7071 C2=0.7071 2.4293 + + R1=1 Vin Table 46 Vs C3=1.4142 - Figure 44 R2=1 C4=0.3536 - Design Example for Kerwin’s Circuit Pole/Zero Analysis Results for Kerwin’s Circuit Poles (rad/sec) Poles (Hz) Real Imaginary Real Imaginary -5.003939e-02 9.987214e-01 -7.964016e-03 1.589515e-01 -5.003939e-02 -9.987214e-01 -7.964016e-03 -1.589515e-01 -1.414227e+00 0.000000e+00 -2.250812e-01 0.000000e+00 0.000000e+00 -1.414227e+00 0.000000e+00 -2.250812e-01 0.000000e+00 1.414227e+00 0.000000e+00 2.250812e-01 -1.414227e+00 0.000000e+00 -2.250812e-01 0.000000e+00 Constant Factor = 1.214564e+00 Example 3 – High-Pass Butterworth Filter This example is a HSPICE input file, for pole/zero analysis of a fourth-order high-pass Butterworth filter. This file is in <\$installdir>/demo/hspice/filters/fhp4th.sp. Table 47 on page 383 shows the analysis results. 382 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 13: Pole/Zero Analysis Pole/Zero Analysis Examples R2=0.3826 C Vin Figure 45 Table 47 C2 + - R1=2.613 R4=0.9238 C3 C4 R3=1.0825 + RL V(10) Fourth-Order High-Pass Butterworth Filter Pole/Zero Analysis Results for High-Pass Butterworth Filter Poles (rad/sec) Poles (Hz) Real Imaginary Real Imaginary -3.827019e-01 -9.240160e-01 -6.090889e-02 1.470617e-01 -3.827019e-01 9.240160e-01 -6.090890e-02 -1.470617e-01 -9.237875e-01 3.828878e-01 -1.470254e-01 6.093849e-02 -9.237875e-01 -3.828878e-01 -1.470254e-01 -6.093849e-02 0.000000e+00 0.000000e+00 0.000000e+00 0.000000e+00 0.000000e+00 0.000000e+00 0.000000e+00 0.000000e+00 0.000000e+00 0.000000e+00 0.000000e+00 0.000000e+00 0.000000e+00 0.000000e+00 0.000000e+00 0.000000e+00 Constant Factor = 1.000000e+00 Example 4 – CMOS Differential Amplifier This example is based on HSPICE demonstration netlist mcdiff.sp, which is available in directory \$<installdir>/demo/hspice/apps. Table 48 on page 385 shows the analysis results. HSPICE® User Guide: Simulation and Analysis B-2008.09 383 Chapter 13: Pole/Zero Analysis Pole/Zero Analysis Examples *file: mcdiff.sp cmos differential amplifier * analysis : ac(20khz-500mhz), pole-zero * mos level=5 * .options acct scale=1e-6 scalm=1e-6 wl opts post .pz v(5) vin vin 7 0 0 ac 1 .ac dec 10 20k 500meg .probe ac vdb(5) vp(5) m1 4 0 6 6 mn 100 10 2 2 m2 5 7 6 6 mn 100 10 2 2 m3 4 4 1 1 mp 60 10 1.5 1.5 m4 5 4 1 1 mp 60 10 1.5 1.5 m5 6 3 2 2 mn 50 10 1.0 1.0 vdd 1 0 5 vss 2 0 -5 vgg 3 0 -3 rin 7 0 1 .model mn nmos level=5 vt=1 ub=700 frc=0.05 tox=800 dnb=1.6e16 + xj=1.2 latd=0.7 cj=0.13 phi=1.2 tcv=0.003 .model mp pmos level=5 vt=-1 ub=245 frc=0.25 tox=800 dnb=1.3e15 + xj=1.2 latd=0.9 cj=0.09 phi=0.5 tcv=0.002 .end The following is an equivalent example in HSPICE RF: 384 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 13: Pole/Zero Analysis Pole/Zero Analysis Examples * HSPICE RF example CMOS DIFFERENTIAL AMPLIFIER .OPTION PIVOT SCALE=1.e-6 SCALM=1.e-6 HQR .PZ V(5) VIN VIN 7 0 0 AC 1 .AC DEC 10 20K 500MEG M1 4 0 6 6 MN 100 10 2 2 M2 5 7 6 6 MN 100 10 2 2 M3 4 4 1 1 MP 60 10 1.5 1.5 M4 5 4 1 1 MP 60 10 1.5 1.5 M5 6 3 2 2 MN 50 10 1.0 1.0 VDD 1 0 5 VSS 2 0 -5 VGG 3 0 -3 RIN 7 0 1 .MODEL MN NMOS LEVEL=5 VT=1 UB=700 FRC=0.05 DNB=1.6E16 + XJ=1.2 LATD=0.7 CJ=0.13 PHI=1.2 TCV=0.003 TOX=800 .MODEL MP PMOS LEVEL=5 VT=-1 UB=245 FRC=0.25 TOX=800 + DNB=1.3E15 XJ=1.2 LATD=0.9 CJ=0.09 PHI=0.5 TCV=0.002 .END Table 48 Pole/Zero Analysis Results for CMOS Differential Amplifier Poles (rad/sec) Poles (Hz) Real Imaginary Real Imaginary -1.798766e+06 0.000000e+00 -2.862825e+05 0.000000e+00 -1.126313e+08 -6.822910e+07 -1.792583e+07 -1.085900e+07 -1.126313e+08 6.822910e+07 -1.792583e+07 1.085900e+07 -1.315386e+08 7.679633e+07 -2.093502e+07 1.222251e+07 -1.315386e+08 -7.679633e+07 -2.093502e+07 -1.222251e+07 7.999613e+08 0.000000e+00 1.273178e+08 0.000000e+00 Constant Factor = 3.103553e-01 HSPICE® User Guide: Simulation and Analysis B-2008.09 385 Chapter 13: Pole/Zero Analysis Pole/Zero Analysis Examples +5v 1 M3 M4 V(5) 4 5 M M2 7 Vin 6 3 Rin M5 2 -5v Figure 46 CMOS Differential Amplifier Example 5 – Simple Amplifier This example is a HSPICE input file for pole/zero analysis of an equivalent circuit for a simple amplifier with: ■ RS¼=RPI=RL=1000 ohms ■ gm=0.04 mho ■ CMU=1.0e-11 farad ■ CPI¼=1.0e-9 farad The file is in <\$installdir>/demo/hspice/apps/ampg.sp. Table 49 shows the analysis results. 386 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 13: Pole/Zero Analysis Pole/Zero Analysis Examples Rs Vin Figure 47 Table 49 Cμ Rn Cn + V - gV RL + V3 - Simple Amplifier Pole/Zero Analysis Results for Amplifier Poles (rad/sec) Poles (Hz) Real Imaginary Real Imaginary -1.412555+06 0.000000e+00 -2.248151e+05 0.000000e+00 -1.415874+08 0.000000e+00 -2.253434e+07 0.000000e+00 4.000000e+09 0.000000e+00 6.366198e+08 0.000000e+00 Constant Factor = 1.000000e+06 Example 6— Active Low-Pass Filter This example is based on demonstration netlist flp9th.sp, which is available in directory \$<installdir>/demo/hspice/filters. It is for a pole/zero analysis of an active ninth-order low-pass filter by using the ideal operational amplifier element. This example performs an AC analysis. Table 50 is the analysis results. HSPICE® User Guide: Simulation and Analysis B-2008.09 387 Chapter 13: Pole/Zero Analysis Pole/Zero Analysis Examples * file flp9th.sp----9th order low-pass filter * * reference: jiri vlach and kishore singhal, 'computer * methods for circuit analysis and design', * van nostrand reinhold co., 1983, pages 142 * and 494 to 496. * * pole/zero analysis and using vcvs as an ideal op-amp. * for just pole/zero analysis .ac statement is not required. vin in 0 ac 1 .ac dec 100 1 100k .print vm(out) vm(in) vp(out) .probe ac vdb(out,in) par('db(vm(out)/vm(in))') .pz v(out) vin .options post dcstep=1e3 + x0r=-1.23456e+3 x1r=-1.23456e+2 x2r=1.23456e+3 + fscal=1e-6 gscal=1e3 cscal=1e9 lscal=1e3 .subckt fdnr 1 r1=2k c1=12n r4=4.5k r1 1 2 r1 c1 2 3 c1 r2 3 4 3.3k r3 4 5 3.3k r4 5 6 r4 c2 6 0 10n eop1 5 0 2 4 level=1 eop2 3 0 6 4 level=1 .ends * rs in 1 5.4779k r12 1 2 4.44k r23 2 3 3.2201k r34 3 4 3.63678k r45 4 out 1.2201k c5 out 0 10n x1 1 fdnr r1=2.0076k c1=12n r4=4.5898k x2 2 fdnr r1=5.9999k c1=6.8n r4=4.25725k x3 3 fdnr r1=5.88327k c1=4.7n r4=5.62599k x4 4 fdnr r1=1.0301k c1=6.8n r4=5.808498k .end The following is an equivalent example in HSPICE RF: 388 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 13: Pole/Zero Analysis Pole/Zero Analysis Examples * HSPICE RF example VIN IN 0 AC 1 .PZ V(OUT) VIN .AC DEC 50 .1K 100K .OPTION PLST DCSTEP=1E3 XOR=-1.23456E+3 X1R=-1.23456E+2 + X2R=1.23456E+3 FSCAL=1E-6 GSCAL=1E3 CSCAL=1E9 LSCAL=1E3 .PRINT AC VDB(OUT) .SUBCKT OPAMP IN+ IN- OUT GM1=1 RI=1K CI=26.6U GM2=1.33333 RL=75 RII IN+ IN- 2MEG RI1 IN+ 0 500MEG RI2 IN- 0 500MEG G1 1 0 IN+ IN- GM1 C1 1 0 CI R1 1 0 RI G2 OUT 0 1 0 GM2 RLD OUT 0 RL .ENDS .SUBCKT FDNR 1 R1=2K C1=12N R4=4.5K RLX=75 R1 1 2 R1 C1 2 3 C1 R2 3 4 3.3K R3 4 5 3.3K R4 5 6 R4 C2 6 0 10N XOP1 2 4 5 OPAMP XOP2 6 4 3 OPAMP .ENDS \$ \$ RS IN 1 5.4779K R12 1 2 4.44K R23 2 3 3.2201K R34 3 4 3.63678K R45 4 OUT 1.2201K C5 OUT 0 10N X1 1 X2 2 X3 3 X4 4 .END FDNR FDNR FDNR FDNR R1=2.0076K C1=12N R4=4.5898K R1=5.9999K C1=6.8N R4=4.25725K R1=5.88327K C1=4.7N R4=5.62599K R1=1.0301K C1=6.8N R4=5.808498K HSPICE® User Guide: Simulation and Analysis B-2008.09 389 Chapter 13: Pole/Zero Analysis Pole/Zero Analysis Examples 500 M Out + In+ 2V1 4 V 75 2 3 26.6mf V2 1k 2M - In500 Figure 48 Linear Model of the 741C Operational Amplifier + 1 R1 - 3 2 R3 R2 4 R4 6 C2 5 C1 +• Figure 49 390 FDNR Subcircuit HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 13: Pole/Zero Analysis Pole/Zero Analysis Examples RS 1 R12 2 R23 3 R34 4 R45 In Out X1 Figure 50 Table 50 X2 X3 X4 C5 Active Realization of the Low-Pass Filter Pole/Zero Analysis Results for the Active Low-Pass Filter Poles (rad/sec) Poles (Hz) Real Imaginary Real Imaginary -4.505616e+02 -2.210451e+04 -7.170911e+01 -3.518042e+03 -4.505616e+02 2.210451e+04 -7.170911e+01 3.518042e+03 -1.835284e+03 2.148369e+04 -2.920944e+02 3.419236e+03 -1.835284e+03 -2.148369e+04 -2.920944e+02 -3.419236e+03 -4.580172e+03 1.944579e+04 -7.289571e+02 3.094894e+03 -4.580172e+03 -1.944579e+04 -7.289571e+02 -3.094894e+03 -9.701962e+03 1.304893e+04 -1.544115e+03 2.076802e+03 -9.701962e+03 -1.304893e+04 -1.544115e+03 -2.076802e+03 -1.353908e+04 0.000000e+00 -2.154811e+03 0.000000e+00 -3.668995e+06 -3.669793e+06 -5.839386e+05 -5.840657e+05 -3.668995e+06 3.669793e+06 -5.839386e+05 5.840657e+05 -3.676439e+06 -3.676184e+06 -5.851234e+05 -5.850828e+05 -3.676439e+06 3.676184e+06 -5.851234e+05 5.850828e+05 HSPICE® User Guide: Simulation and Analysis B-2008.09 391 Chapter 13: Pole/Zero Analysis Pole/Zero Analysis Examples Table 50 Pole/Zero Analysis Results for the Active Low-Pass Filter Poles (rad/sec) Poles (Hz) Real Real Imaginary -3.687870e+06 3.687391e+06 -5.869428e+05 5.868665e+05 -3.687870e+06 -3.687391e+06 -5.869428e+05 -5.868665e+05 -3.695817e+06 -3.695434e+06 -5.882075e+05 -5.881466e+05 -3.695817e+06 +3.695434e+06 -5.882075e+05 5.881466e+05 -3.220467e-02 -2.516970e+04 -5.125532e-03 -4.005882e+03 -3.220467e-02 2.516970e+04 -5.125533e-03 4.005882e+03 2.524420e-01 -2.383956e+04 4.017739e-02 -3.794184e+03 2.524420e-01 2.383956e+04 4.017739e-02 3.794184e+03 1.637164e+00 2.981593e+04 2.605627e-01 4.745353e+03 1.637164e+00 -2.981593e+04 2.605627e-01 -4.745353e+03 4.888484e+00 4.852376e+04 7.780265e-01 7.722796e+03 4.888484e+00 -4.852376e+04 7.780265e-01 -7.722796e+03 -3.641366e+06 -3.642634e+06 -5.795413e+05 -5.797432e+05 -3.641366e+06 3.642634e+06 -5.795413e+05 5.797432e+05 -3.649508e+06 -3.649610e+06 -5.808372e+05 -5.808535e+05 -3.649508e+06 3.649610e+06 -5.808372e+05 5.808535e+05 -3.683700e+06 3.683412e+06 -5.862790e+05 5.862333e+05 -3.683700e+06 -3.683412e+06 -5.862790e+05 -5.862333e+05 -3.693882e+06 3.693739e+06 5.878995e+05 5.878768e+05 -3.693882e+06 392 Imaginary -3.693739e+06 -5.878995e+05 -5.878768e+05 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 13: Pole/Zero Analysis Pole/Zero Analysis Examples Table 50 Pole/Zero Analysis Results for the Active Low-Pass Filter Poles (rad/sec) Real Poles (Hz) Imaginary Real Imaginary Constant Factor = 4.451586e+02 Figure 51 9th Order Low-Pass Filter Response The graph in Figure 51 shows overall response of the low-pass filter. HSPICE® User Guide: Simulation and Analysis B-2008.09 393 Chapter 13: Pole/Zero Analysis References References [1] Desoer, Charles A. and Kuh, Ernest S. Basic Circuit Theory. New York: McGraw-Hill.1969. Chapter 15. [2] Van Valkenburg, M. E. Network Analysis. Englewood Cliffs, New Jersey: Prentice Hall, Inc., 1974, Chapters 10 & 13. [3] R.H. Canon, Jr. Dynamics of Physical Systems. New York: McGraw-Hill, 1967. This text describes electrical, mechanical, pneumatic, hydraulic, and mixed systems. [4] B.C. Kuo. Automatic Control Systems. Englewood Cliffs, New Jersey: Prentice-Hall, 1975. This source discusses control system design, and provides background material about physical modeling. [5] L.T. Pillage, and R.A. Rohrer. “Asymptotic Waveform Evaluation for Timing Analysis”, IEEE Trans CAD. Apr. 1990, pp. 352 - 366. This paper is a good references about interconnect transfer function modeling, and discusses extracting transfer functions for timing analysis. [6] S. Lin, and E.S. Kuh. “Transient Simulation of Lossy Interconnects Based on the Recursive Convolution Formulation”, IEEE Trans CAS. Nov. 1992, pp. 879 - 892. This paper is another source for how to model interconnect transfer functions. [7] Muller, D. E., A Method for Solving Algebraic Equations Using a Computer, Mathematical Tables, and Other Aids to Computation (MTAC). 1956, Vol. 10,. pp. 208-215. [8] Temes, Gabor C. and Mitra, Sanjit K. Modern Filter Theory And Design. J. Wiley, 1973, page 74. [9] Temes, Gabor C. and Lapatra, Jack W. Circuit Synthesis And Design, McGraw-Hill. 1977, page 301, example 7-6. [10] Temes, Gabor C. and Mitra, Sanjit K., Modern Filter Theory And Design. J. Wiley, 1973, page 348, example 8-3. [11] Desoer, Charles A. and Kuh, Ernest S. Basic Circuit Theory. McGraw-Hill, 1969, page 613, example 3. [12] Vlach, Jiri and Singhal, Kishore. Computer Methods For Circuit Analysis and Design. Van Nostrand Reinhold Co., 1983, pages 142, 494-496. 394 HSPICE® User Guide: Simulation and Analysis B-2008.09 14 14 Transient Analysis Describes how to use transient analysis to compute the circuit solution. Transient analysis computes the circuit solution, as a function of time, over a time range specified in the .TRAN statement. For descriptions of individual HSPICE commands referenced in this chapter, see the HSPICE Reference Manual: Commands and Control Options. These topics are presented in the following sections: ■ Simulation Flow ■ Overview of Transient Analysis ■ Transient Control Options ■ Simulation Speed and Accuracy Using the RUNLVL Option ■ Numerical Integration Algorithm Controls ■ Dynamic Check Using the .BIASCHK Statement ■ Troubleshooting: Internal Timestep, Measurement Errors Simulation Flow Figure 52 on page 396 illustrates the simulation flow for transient analysis in HSPICE. HSPICE® User Guide: Simulation and Analysis B-2008.09 395 Chapter 14: Transient Analysis Overview of Transient Analysis Simulation Experiment DC Transient AC Time-sweep simulation .BIASCHK Options Method BYPASS MAXORD METHOD PURETP TRCON Figure 52 Tolerance and Limit BE GEAR TRAP BDF ACCURATE GMIN AUTOSTOP GSHUNT ITL4=x BKPSIZ MBYPASS BYTOL MU CSHUNT RUNLVL DELMAX Output POST INTERP Transient Analysis Simulation Flow Overview of Transient Analysis Transient analysis simulates a circuit at a specific time. Some of its algorithms, control options, convergence-related issues, and initialization parameters are different than those used in DC analysis. However, a transient analysis first performs a DC operating point analysis, unless you specify the UIC option in the .TRAN statement. Unless you set the initial circuit operating conditions, some circuits (such as oscillators, or circuits with feedback) do not have stable operating point solutions. For these circuits, either: ■ Break the feedback loop, to calculate a stable DC operating point, or ■ Specify the initial conditions in the simulation input. For setting initial conditions, see Initial Conditions and UIC Parameters. 396 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 14: Transient Analysis Overview of Transient Analysis Example In the following example, the UIC parameter (in the .TRAN statement) bypasses the initial DC operating point analysis. The .OP statement calculates the transient operating point (at t=20 ns), during the transient analysis. .TRAN 1ns 100ns UIC .OP 20ns In a transient analysis, the internal timestep too small error message indicates that the circuit failed to converge. The cause of this convergence failure might be that stated initial conditions are not close enough to the actual DC operating point values. Use the commands in this chapter to help achieve convergence in a transient analysis. See also: Troubleshooting: Internal Timestep, Measurement Errors at the end of this chapter. Data-Driven vs. Outer Parameter Sweeps The following defines the differences between a data-driven sweep and an outer parameter sweep. Data-Driven Sweep The use of a data set allows the sweeping of both nonuniform values and multiple parameters. You will need to specify each value varied in the simulation. This method generates one output file for the entire simulation. When viewing signals, the traces correspond to each parameter sweep. Example .tran 1n 100n sweep data=mydata .data mydata param1 param2 ... val1 vala ... val2 valb ... .... .enddata Parameter Sweep When the values of a parameter can be expressed using decade, octave, linear, or point-of-interest variation, you can use the sweep keyword to control the parameter. This method does not allow for multiple parameters to be swept. Similar to the data-driven sweep, only one output file is created, with the signals having multiple traces. Be sure to sequence the var (param) before the type (DEC, LIN). HSPICE® User Guide: Simulation and Analysis B-2008.09 397 Chapter 14: Transient Analysis Overview of Transient Analysis Examples In this example, param will be varied 10 times for each decade from 1u to 10u and a transient analysis will be run for each value. .tran 1n 100n sweep param DEC 10 1u 10u In this example, param will be varied 5 equal times from 1u to 10u with a transient analysis for each value. .tran 1n 100n sweep param LIN 5 1u 10u Similar to the data-driven sweep, only one output file will be created. The signals will also be multi-membered. Sweeping Multiple Parameters Although HSPICE does not directly provide the facility to sweep multiple parameters, it does offer the .DATA table structure. A linked perl script is available to allow you to specify lists of parameters and values at https://solvnet.synopsys.com/retrieve/021478.html This script will create a .DATA table with all permutations of the listed values. It also allows you to create .ALTERs instead of a .DATA table, if preferred. For usage details, run hspice_param_sweeper -h. The script's output goes to STDOUT, so redirect it to a file, for example: hspice_param_sweeper > param_sweep.sp), and then .INCLUDE the file into your HSPICE netlist. If you choose to create .ALTERs, make sure you .INCLUDE them at the very end of your netlist. If you create a .DATA table, you can invoke it as follows: .TRAN 10p 100n SWEEP DATA=sweeper_params Here is a sample input to the script. vddr: 1.1, 1.0, 0.9 vssr: 0.0 temp: 0, 55, 100 Note that temp is a special parameter that will sweep the simulation temperature. This example will produce a .DATA table with 9 rows (3*1*3) containing all combinations of the listed parameter values, or 1 base sim + 8 .ALTERs if the -alter option is used. Here is the output produced by the sample input. 398 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 14: Transient Analysis Overview of Transient Analysis .DATA sweeper_params temp vddr vssr 0 1.1 0.0 55 1.1 0.0 100 1.1 0.0 0 1.0 0.0 55 1.0 0.0 100 1.0 0.0 0 0.9 0.0 55 0.9 0.0 100 0.9 0.0 .ENDDATA After you download the script named hspice_param_sweeper.gz (right-click and select “Save Target As...”), be sure to modify the first line of the script to point to your local installation of perl. The default path should work on most systems. Specifying Data Driven Timesteps Instead of using a constant timestep in a .TRAN statement, you can specify the timesteps using an inline data statement for the transient simulation. The data defined in the .DATA statement should define the time point and current value for a PWL current source. In the following example, the .DATA statement tstep_val defines the time step, step_val and the current value, ival. HSPICE uses the timesteps defined in the .DATA statement during the transient simulation. Ipwl nd1 0 PWL (step_val ival) .tran DATA = tstep_val .DATA tstep_val step_val ival + 10p 1m + 30p 10m + 70P 10m + 100p 100m .ENDDATA The timestep value specified in the data table (DATA=tstep_val) controls the print intervals. Transient Analysis Output .print tran ov1 [ov2 ... ovN] .probe tran ov1 [ov2 ... ovN] .measure tran measspec HSPICE® User Guide: Simulation and Analysis B-2008.09 399 Chapter 14: Transient Analysis Overview of Transient Analysis The ov1, ... ovN output variables can include the following: ■ V(n): voltage at node n. ■ V(n1<,n2>): voltage between the n1 and n2 nodes. ■ Vn(d1): voltage at nth terminal of the d1 device. ■ In(d1): current into nth terminal of the d1 device. ■ ‘expression’: expression, involving the plot variables above You can use wildcards to specify multiple output variables in a single command. Output is affected by .OPTION POST or .OPTION PROBE. Parameter *.print Description Writes the output from the .PRINT statement to a *.print file. HSPICE does not generate a *.print# file. ■ ■ ■ ■ *.tr# The header line contains column labels. The first column is time. The remaining columns represent the output variables specified with .PRINT. Rows that follow the header contain the data values for simulated time points. Writes output from the .PROBE, .PRINT, or .MEASURE statement to a *.tr# file. Transient Analysis of an RC Network Follow these steps to run a transient analysis of a RC network with a pulse source, a DC source, and an AC source: 1. Type the following netlist into a file named quickTRAN.sp. A SIMPLE TRANSIENT RUN .OPTION LIST NODE POST .OP .TRAN 10N 2U .PRINT TRAN V(1) V(2) I(R2) I(C1) V1 1 0 10 AC 1 PULSE 0 5 10N 20N 20N 500N 2U R1 1 2 1K R2 2 0 1K C1 2 0 .001U .END 400 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 14: Transient Analysis Overview of Transient Analysis This example is based on demonstration netlist quickTRAN.sp, which is available in directory \$<installdir>/demo/hspice/apps. Note: The V1 source specification includes a pulse source. For the syntax of pulse sources and other types of sources, see Chapter 9, Sources and Stimuli. 2. To run HSPICE, type the following: hspice quickTRAN.sp > quickTRAN.lis 3. To examine the simulation results and status, use an editor and view the .lis and .st0 files. 4. Run WaveView and open the .sp file. 5. From the File menu, select File > Import Waveform > File. 6. Select the quickTRAN.tr0 file from the Open: Waveform Files window. 7. Display the voltage at nodes 1 and 2 on the x-axis. Figure 53 shows the waveforms. Figure 53 Voltages at RC Network Circuit Node 1 and Node 2 HSPICE® User Guide: Simulation and Analysis B-2008.09 401 Chapter 14: Transient Analysis Overview of Transient Analysis Transient Analysis of an Inverter As a final example, you can analyze the behavior of the simple MOS inverter shown in Figure 54. VCC VCC + _ M1 IN VIN OUT CLOAD 0.75 pF + _ M2 Figure 54 MOS Inverter Circuit Follow these steps to analyze this behavior: 1. Type the following netlist data into a file named quickINV.sp. Inverter Circuit .OPTION LIST NODE POST .TRAN 200P 20N .PRINT TRAN V(IN) V(OUT) M1 OUT IN VCC VCC PCH L=1U W=20U M2 OUT IN 0 0 NCH L=1U W=20U VCC VCC 0 5 VIN IN 0 0 PULSE .2 4.8 2N 1N 1N 5N 20N CLOAD OUT 0 .75P .MODEL PCH PMOS LEVEL=1 .MODEL NCH NMOS LEVEL=1 .END You can find the complete netlist for this example in directory \$<installdir>/ demo/hspice/apps/quickINV.sp. 2. To run HSPICE, type the following: hspice quickINV.sp > quickINV.lis 3. Use WaveView to examine the voltage waveforms, at the inverter IN and OUT nodes. 402 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 14: Transient Analysis Transient Control Options Figure 55 on page 403 shows the waveforms. Figure 55 Voltage at MOS Inverter Node 1 and Node 2 Transient Control Options Method, tolerance, and limit options in this section modify the behavior of transient analysis integration routines. Delta is the internal timestep. TSTEP and TSTOP are the step and stop values in the .TRAN statement. HSPICE® User Guide: Simulation and Analysis B-2008.09 403 Chapter 14: Transient Analysis Simulation Speed and Accuracy Using the RUNLVL Option Table 51 lists the options for RUNLVL. Table 51 Transient Control Options with RUNLVL Turned On, by Category Method Tolerance and Limit Output BYPASS MAXORD METHOD= Backward-Euler (BE) GEAR TRAP BDF PURETP TRCON ACCURATE AUTOSTOP BKPSIZ BYTOL CSHUNT DELMAX POST GMIN GSHUNT ITL4 MBYPASS MAXAMP MU RUNLVL INTERP For discussion of METHOD options, see Numerical Integration Algorithm Controls on page 408. Simulation Speed and Accuracy Using the RUNLVL Option Convergence is the ability to solve a set of circuit equations within specified tolerances and within a specified number of iterations. How quickly the simulator converges, is often a primary concern to a designer—especially for preliminary design trials. So designers may willingly sacrifice some accuracy for simulations that converge quickly. The RUNLVL algorithm, which is on by default in HSPICE, focuses on a balance between speed and accuracy. The RUNLVL algorithm: 1. Uses an enhanced Local Truncation Error (LTE) method based on nodal voltage for timestep control. This is advantageous because voltage is the target result users want from a simulation, and there is a clear mathematical relation between error tolerance and time step. 2. Adopts a new Newton-Raphson (NR) iteration method for transient analysis. It not only improves the convergence but also makes the convergence faster. 3. Improves the BYPASS algorithm, as well. Transient analysis performance may be improved up to 20X without any loss of accuracy by using the RUNLVL option compared to RUNLVL=0. For discussion of RUNLVL=0, see Appendix D, Transient Simulation with RUNLVL=0. 404 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 14: Transient Analysis Simulation Speed and Accuracy Using the RUNLVL Option RUNLVL Features The RUNLVL algorithm provides the following characteristics: ■ Simplifies accuracy control by setting RUNLVL values between 1 and 6 with 6 discrete settings (1=fastest, 6=most accurate). ■ Avoids interpolation error in .MEASURE statements by using the interpolating polynomial used by the time integration method. ■ Dynamically checks for correct handling of input signals and controlled sources between computed time steps to avoid small time step being set before transient simulation start. ■ Allows HSPICE to take time steps no larger than (Tstop-Tstart)/20. DELMAX is automatically set to (Tstop-Tstart)/20 if there is no specific setting of DELMAX. The effect is that, for example, HSPICE can take larger time steps for flat regions. The RUNLVL algorithm scales all simulation tolerances simultaneously and affects time step control, convergence, and model bypass all at once. This algorithm is activated only by .option RUNLVL=value. Higher values of RUNLVL result in smaller time steps (more Newton-Raphson iterations) to meet stricter error tolerances, and higher simulation accuracy. A valid value for .OPTION RUNLVL is an integer from 1 to 6. Values outside of this range will cause an error. The default value for RUNLVL is 3. This is the recommended starting setting. Higher values are for simulations requiring high accuracy. Lower values are used for simulating pure digital or mostly digital circuits. Setting RUNLVL=0 will turn off the option. If there are multiple settings of RUNLVL options, the last one set is used. The .OPTION RUNLVL invokes the advanced simulation algorithm, with the default value of RUNLVL=3. This is the recommended starting setting. However, you can set it to a higher value if the circuit type is pure analog and/or the simulation needs high accuracy. Table 52 Guidelines for RUNLVL Settings Circuit type RUNLVL Setting Digital RUNLVL=1-3 Analog or mixed signal accuracy RUNLVL=3-5 Cell characterization RUNLVL=5-6 HSPICE® User Guide: Simulation and Analysis B-2008.09 405 Chapter 14: Transient Analysis Simulation Speed and Accuracy Using the RUNLVL Option The RUNLVL flag and its effective value is reported in a *.lis file. The RUNLVL option is automatically set in the \$install_dir/hspice/hspice.ini file, which is generated during the installation process. All HSPICE simulations first try to find ONE implicit hspice.ini file and take it as the first include file; the search order for hspice.ini is: 1. Current working directory 2. User's home directory 3. \$install_dir/hspice directory Interactions Between .OPTION RUNLVL and Other Options Refer to Table 53 for information on how RUNLVL affects the values of other options. Since the latest algorithm invoked by RUNLVL sets the timestep and error tolerance internally, many transient error tolerance and timestep control options are no longer valid; furthermore, to assure the greatest efficiency of the RUNLVL algorithm, you should let the new engine manage everything itself. Options that are recommended not to tune are listed in the table, as well. Note: If RUNLV is set without value, its value defaults to =3. RNLVL=0 must be set explicitly. (See Appendix D, Transient Simulation with RUNLVL=0.) Table 53 Options and Interactions Option Default value with RUNLVL=3 ABSV/VNTOL 50u 50u ABSVAR 500m 500m ACCURATE* a 0 0 BYPASS* a 2 2 CHGTOL 1.0f 1.0f DI 100 100 DVDT 4 4 x DVTR 406 Default value without RUNLVL User definition ignored 1.0k 1.0k Recommend not to tune x x x x x HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 14: Transient Analysis Simulation Speed and Accuracy Using the RUNLVL Option Table 53 Options and Interactions (Continued) Option Default value without RUNLVL Default value with RUNLVL=3 User definition ignored Recommend not to tune FAST** b 0 0 x FS 250m 250m FT 250m 250m x IMIN/ITL3 3 3 x LVLTIM 1 4 x METHOD*** c TRAP TRAP RELQ 10m 10m RELTOL 1.0m 1.0m x RELV 1.0m 1.0m x RELVAR 300.0m 300.0m x RMAX 5 5 x RMIN 1.0n 1.0n x x x a. * ACCURATE and BYPASS notes: 1. If .option ACCURATE is set, then the RUNLVL value is limited to 5 or 6. Specifying a RUNLVL less than 5 results in a simulation at RUNLVL=5. When both ACCURATE and RUNLVL are set, the RUNLVL algorithm will be used. 2. When RUNLVL is set, BYPASS is set to 2. Users can re-define the BYPASS value by setting .option BYPASS=<value>; this behavior is independent of the order of RUNLVL and BYPASS; b. **The FAST option is disabled by the RUNLVL option; setting the RUNLVL value to 1 is comparable to setting the FAST option. c. ***RUNLVL can work with METHOD=GEAR; in cases where GEAR only determines the numeric integration method during transient analysis, the other options that were previously set by GEAR (when there is no RUNLVL) now are determined by the RUNLVL mode. This behavior is independent of the order of RUNLVL and METHOD. See the following table. HSPICE® User Guide: Simulation and Analysis B-2008.09 407 Chapter 14: Transient Analysis Numerical Integration Algorithm Controls The interactions of RUNLVL and GEAR are shown in Table 54. Table 54 RUNLVL option and GEAR method interactions Option GEAR without RUNLVL GEAR with RUNLVL=3 BYPASS 0 2 BYTOL 50u 100u LVLTIM 2 Disabled by runlvl MAXORD 2 3 for RUNLVL=6 2 for RUNLVL=1-5 MBYPASS 1 2 RMAX 2 Disabled by runlvl HSPICE maintains all the algorithms of RUNLVL=0 for backward compatibility consideration. See Appendix D, Transient Simulation with RUNLVL=0. Numerical Integration Algorithm Controls In HSPICE transient analysis, you can select one of several options solve the circuit differential algebraic equations: ■ Backward-Euler ■ Gear ■ Trapezoidal ■ BDF Table 55 Integration Method Integration Option Settings Algorithm Backward- METHOD=GEAR MAXORD=1 or Euler (BE) METHOD=GEAR MU=0 Backward-Euler only GEAR 408 Comments Combines GEAR and BE 2nd/3rd order increases accuracy METHOD=GEAR METHOD=GEAR MAXORD=2|3 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 14: Transient Analysis Numerical Integration Algorithm Controls Table 55 Integration Method (Continued) Integration Option Settings Algorithm Comments TRAP METHOD=TRAP METHOD=TRAP PURETP Combines Trapezoidal and BE Trapezoidal only BDF METHOD=BDF Higher order integration (Backward Differentiation Formulae) Each algorithm has advantages and disadvantages. The trapezoidal is often the preferred algorithm because of its high accuracy level and low simulation time. The pure trapezoidal (PURETP) is recommended for oscillators. The Gear method is an appropriate algorithm for convergence. 2nd-order GEAR is more accurate than Backward-Euler and 3rd-order GEAR is more accurate than 2nd-order GEAR. The GEAR is recommended for those circuit simulations that require high accuracy on current such as leakage current measurement. If the circuit fails to converge using the Trapezoidal integration method, HSPICE uses the GEAR method to run the transient analysis again from time=0. This process is called autoconvergence. The BDF method is an high order integration method based on the backward differentiation formulae. The key features include: variable order, variable step size, and high order polynomial interpolation. Two tolerance options are available to the user for the BDF method: .OPTIONS BDFRTOL (relative) and BDFATOL (absolute); each has a default of 1e-3. The BDF limitations are listed below. METHOD=BDF supports the following models only: ■ MOSFET, levels 1-54 ■ BJT, level 1 only ■ Diodes, all ■ Resistors, all ■ Capacitors, excludes DC block ■ Independent sources: V and I ■ Dependent sources: E/F/G/H HSPICE® User Guide: Simulation and Analysis B-2008.09 409 Chapter 14: Transient Analysis Dynamic Check Using the .BIASCHK Statement ■ L, excludes AC choke ■ K, excludes magnetic core, ideal transformer Note: BDF issues a warning in the .lis file if it encounters an unsupported model. The message is similar to: WARNING!!!, netlist contains ‘unsupported models’, HSP-BDF is disabled. Dynamic Check Using the .BIASCHK Statement The .BIASCHK statement can monitor the voltage bias, current, device-size, expression and region during transient analysis, and reports: ■ Element name ■ Time ■ Terminals ■ Bias that exceeds the limit ■ Number of times the bias exceeds the limit for an element For the syntax and description of this statement, see the .BIASCHK command in the HSPICE Reference Manual: Commands and Control Options. HSPICE saves the information as both a warning and a BIASCHK summary in the *.lis file. You can use this command only for active elements and capacitors. You can also use .OPTION BIASFILE and .OPTION BIAWARN with a .BIASCHK statement. The following limitations apply to the .BIASCHK statement: ■ .BIASCHK is only supported for diode, jfet, nmos, pmos, bjt, and c models, as well as subcircuits. ■ For a device-size check, only W and L MOSFET models are supported. ■ Wildcards in element and model names, and except definitions are supported but not in expressions. Four methods are available to check the data with the .BIASCHK command: ■ ■ 410 Limit and noise method Maximum method HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 14: Transient Analysis Dynamic Check Using the .BIASCHK Statement ■ Minimum method ■ Region method Note: The region method of data checking is only supported in MOSFET models. Limit and Noise Method For a transient simulation using the limit and noise method to check the data, use the following syntax: For local_max v(tn-1) > limit_value The bias corresponds anyone of the following two conditions: ■ v(tn-1) > v(tn) && v(tn-1) >= v(tn-2) ■ v(tn-1) >= v(tn) && v(tn-1) > v(tn-2) local_min: The minimum bias after the time last local max occurs. During a transient analysis, the local_max is recorded if it is greater than the limit. In the summary reported after transient analysis, the local_max(current) is replaced with the local_max(next) when the following comparison is true: local_max(current) - local_min < noise && local_max(next) - local_min < noise && local_max(current) < local_max(next) At the end of the simulation, all local_max values are listed as BIASCHK warnings. During other analyses, warnings are issued when the value you want to check is greater than the limit_value you specify. Maximum Method For a transient simulation using the maximum method, use this syntax: For local_max: v(tn-1) > max_value The bias corresponds any one of the following two conditions: ■ v(tn-1) > v(tn) && v(tn-1) >= v(tn-2) ■ v(tn-1) >= v(tn) && v(tn-1) > v(tn-2) HSPICE® User Guide: Simulation and Analysis B-2008.09 411 Chapter 14: Transient Analysis Troubleshooting: Internal Timestep, Measurement Errors During a transient analysis, all local_max values are listed as BIASCHK warnings. During other analyses, warnings are issued when the value you want to check is greater than max_value you specify. Minimum Method For a transient simulation using the minimum method to check the data, use the following syntax: For local_min: v(tn) < min_value The bias corresponds any one of the following two conditions: ■ v(tn-1) < v(tn) && v(tn-1) <= v(tn-2) ■ v(tn-1) <= v(tn) && v(tn-1) < v(tn-2) During a transient analysis, all local_min values are listed as BIASCHK warnings. During other analyses, warnings are issued when the value you want to check is smaller than min_value you specify. Region Method This method is only for MOSFET models. Three regions exist: ■ cutoff ■ linear ■ saturation When the specified transistor enters and exits during transient analysis, the specified region is reported. The biaschk.sp demo example is a netlist that uses the .BIASCHK command for a transient simulation. You can find the sample netlist for this example in: \$installdir/demo/hspice/apps/biaschk.sp Troubleshooting: Internal Timestep, Measurement Errors This section provides the following tips for error recovery: ■ ■ 412 Troubleshooting ‘Time step Too Small’ Errors Troubleshooting .MEASUREMENT Issues HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 14: Transient Analysis Troubleshooting: Internal Timestep, Measurement Errors Troubleshooting ‘Time step Too Small’ Errors These are the usual steps to follow when you get an “internal time step too small” in transient analysis errors. The best approach is to incrementally change the values of these options, one at a time. Note the time immediately following the timestep error in the list file. If your simulation gets further into the run, then the option is beneficial and you may wish to try higher or lower values as appropriate. 1. Be sure you are using the latest version of HSPICE if you can. Improvements are continuously made to convergence algorithms. 2. Comment out all timestep and convergence options you already have and try increasing the value of .OPTION RUNLVL as a first step. The RUNLVL option is turned on by default starting with version 2006.09 to level=3. It implements improved convergence techniques. If a higher RUNLVL such as 5 or 6 is set, try a lower RUNLVL to get convergence. Note: Remove any other convergence options when you use RUNLVL. 3. Increase .OPTION ITL4 This is the number of iterations HSPICE will try at one time point, before giving up and taking a smaller time step. The default is 8. Suggested values: .option itl4 = 50 .option itl4 = 100 Note: .OPTION ITL4 is the same as .OPTION IMAX. 100 is the maximum value. 4. Use GSHUNT and CSHUNT to add small amounts of conductance and or capacitance from each node to ground. Together or alone, these options can help solve timestep too small problems caused by either high-frequency oscillations or numerical noise. .option .option .option .option .option gshunt=1e-13 gshunt=1e-12 gshunt=1e-11 gshunt=1e-10 gshunt=1e-9 HSPICE® User Guide: Simulation and Analysis B-2008.09 cshunt=1e-17 cshunt=1e-16 cshunt=5e-15 cshunt=1e-15 cshunt=1e-14 413 Chapter 14: Transient Analysis Troubleshooting: Internal Timestep, Measurement Errors 5. Increase the timestep value, to step over possible model discontinuities. From original timestep settings, change the .TRAN statement to incrementally increase TSTEP: .tran (2)*tstep tstop .tran (2.5)*tstep tstop .tran (3)*tstep tstop 6. Using .OPTION METHOD=GEAR may help certain high gain analog (such as op-amps) and/or oscillatory circuits (such as a ring oscillators) during transient analysis by changing integration methods. .option method=gear 7. Investigate the device models used. Be sure the version of the models was developed for or qualified with the version of HSPICE you are using. For CMOS devices, make sure you have finite terminal capacitances and resistances. For level 49, be sure you have the model parameters as specified in the following example: (these are samples, not defaults) .model mname nmos level=49 version=3.2 + cj=5e-4 cjsw=1e-10 cgd0=1e-10 cgs0=1e-10 rs=1e-9 rd=1e-9 In the case of BJT device, be sure to have the following model parameters set (again, examples, not defaults). .model mname npn rb=50 r c=.4 re=1e-3 Troubleshooting .MEASUREMENT Issues If .MEASURE results are incorrect compared to the waveforms, the differences you see may be due to one or more of the following issues. ■ You are not comparing the same point. Make sure that the proper nodes and sweep points are being used for each comparison. ■ Do you have .option INTERP set in your netlist? If so, remove it. HSPICE will only save data points at the interval defined by the tstep parameter in the .TRAN statement. For example, for the .TRAN statement: .tran 1n 100n HSPICE will save 100 points at 1ns intervals to the tr0 file. The lack of precision can cause issues with your measurements. 414 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 14: Transient Analysis Troubleshooting: Internal Timestep, Measurement Errors ■ In your .TRAN statement, did you use the START keyword to delay output generation? If so, it should be removed. This option interferes with the .measure calculations. ■ If a .measure statement uses the result of previous .meas statement, then the calculation starts when the previous result is found. Until the previous result is found, it outputs zero. HSPICE® User Guide: Simulation and Analysis B-2008.09 415 Chapter 14: Transient Analysis Troubleshooting: Internal Timestep, Measurement Errors 416 HSPICE® User Guide: Simulation and Analysis B-2008.09 15 15 Spectrum Analysis Describes HSPICE implementation of spectrum analysis based on the Fourier transforms. Spectrum analysis represents a time-domain signal within the frequency domain. It most commonly uses the Fourier transform. A Discrete Fourier Transform (DFT) uses sequences of time values to determine the frequency content of analog signals in circuit simulation. The following topics are covered in these sections: ■ Spectrum Analysis (Fourier Transform) ■ .FFT Analysis ■ Examining the FFT Output ■ AM Modulation ■ Graphical Output ■ Balanced Modulator and Demodulator ■ Signal Detection Test Circuit Spectrum Analysis (Fourier Transform) This section describes the Fourier and FFT Analysis flow for HSPICE. HSPICE® User Guide: Simulation and Analysis B-2008.09 417 Chapter 15: Spectrum Analysis Spectrum Analysis (Fourier Transform) .FOUR Statement Transient Time-sweep simulation .FFT .FOUR Output Variables Display Options .FFT Statement Transient Output Variable V Figure 56 I Time-sweep simulation .FFT .FOUR Display Option P Other Window Format Fourier and FFT Analysis HSPICE provides two different Fourier analyses. ■ ■ 418 .FOUR is the same as is available in SPICE 2G6: a standard, fixed-window analysis tool. The .FOUR statement performs a Fourier analysis, as part of the transient analysis. .FFT is a much more flexible Fourier analysis tool. Use it for analysis tasks that require more detail and precision. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 15: Spectrum Analysis Spectrum Analysis (Fourier Transform) Using the Fourier-Related Statements and Options For syntax and examples, see the following commands and control options in the HSPICE Reference Manual: Commands and Control Options: ■ .FFT ■ .FOUR ■ .MEASURE FFT ■ .OPTION FFT_ACCURATE ■ .OPTION ACCURATE ■ .OPTION FFTOUT ■ .ENVFFT Fourier Accuracy Fourier Accuracy is dependent on transient simulation accuracy. For best accuracy, set small values for .OPTION RMAX or .OPTION DELMAX. For maximum accuracy, set .OPTION DELMAX to 1/(500*frequency). For circuits with very high resonance factors (high-Q circuits, such as crystal oscillators, tank circuits, and active filters), set DELMAX to less than 1/(500*frequency) where, frequency refers to fundamental frequency. Fourier Equation The total harmonic distortion is the square root of the sum of the squares, of the second through ninth normalized harmonic, times 100, expressed as a percent: ⎛9 ⎞ 1- ⎜ 2⎟ THD = ------ ⋅ R R 1 ⎜ ∑ m⎟ ⎝m = 2 ⎠ 1/2 ⋅ 100% The following equation calculates the Fourier coefficients: 9 g( t) = ∑ Cm ⋅ m=0 9 cos ( mt ) + ∑ Dm ⋅ sin ( mt ) m=0 HSPICE® User Guide: Simulation and Analysis B-2008.09 419 Chapter 15: Spectrum Analysis Spectrum Analysis (Fourier Transform) The following equations calculate values for the preceding equation: π Cm 1 = -- ⋅ π ∫ g ( t ) ⋅ cos ( m ⋅ t ) ⋅ dt –π π Dm 1 = -- ⋅ π ∫ g ( t ) ⋅ sin ( m ⋅ t ) ⋅ dt –π 9 g( t) = 9 ∑ Cm ⋅ cos ( m ⋅ t ) + m=0 ∑ Dm ⋅ sin ( m ⋅ t ) m=0 The following equations approximate the C and D values: 500 Cm = ∑ g(n ⋅ 2⋅ π⋅ m⋅ n Δ t ) ⋅ cos ⎛ ---------------------------------- ⎞ ⎝ ⎠ 501 n=0 500 Dm = ∑ g(n ⋅ 2⋅ π⋅ m⋅ n Δ t ) ⋅ sin ⎛ ---------------------------------- ⎞ ⎝ ⎠ 501 n=0 The following equations calculate the magnitude and phase: 2 2 Rm = ( Cm + Dm ) 1 / 2 Cm Φm = arctan ⎛ -------⎞ ⎝ D m⎠ Example 1 The following is input content for an .OP, .TRAN, or .FOUR analysis. This example is based on demonstration netlist four.sp, which is available in the directory \$installdir/demo/hspice/apps. 420 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 15: Spectrum Analysis .FFT Analysis CMOS INVERTER * M1 2 1 0 0 NMOS W=20U L=5U M2 2 1 3 3 PMOS W=40U L=5U VDD 3 0 5 VIN 1 0 SIN 2.5 2.5 20MEG * .MODEL NMOS NMOS LEVEL=3 CGDO=0.2N CGSO=0.2N CGB0=2N .MODEL PMOS PMOS LEVEL=3 CGDO=0.2N CGSO=0.2N CGB0=2N .OP .TRAN 1N 500N .FOUR 20MEG V(2) .PRINT TRAN V(2) V(1) .END Example 2 ****** cmos inverter **** fourier analysis tnom = 25.000 temp = 25.000 **** fourier components of transient response v(2) dc component=2.430D+00 harmonic frequency fourier normalized phase normalized no (hz) component component (deg) phase (deg) 1 20.0000x 3.0462 1.0000 176.5386 0. 2 40.0000x 115.7006m 37.9817m -106.2672 -282.8057 3 60.0000x 753.0446m 247.2061m 170.7288 -5.8098 4 80.0000x 77.8910m 25.5697m -125.9511 -302.4897 5 100.0000x 296.5549m 97.3517m 164.5430 -11.9956 6 120.0000x 50.0994m 16.4464m -148.1115 -324.6501 7 140.0000x 125.2127m 41.1043m 157.7399 -18.7987 8 160.0000x 25.6916m 8.4339m 172.9579 -3.5807 9 180.0000x 47.7347m 15.6701m 154.1858 -22.3528 total harmonic distortion= 27.3791 percent .FFT Analysis The .FFT statement uses the internal time point values. By default, .FFT uses a second-order interpolation to obtain waveform samples, based on the number of points that you specify. You can use windowing functions to reduce the effects of waveform truncation on the spectral content. You can also use the .FFT command to specify: ■ Output format ■ Output frequency range HSPICE® User Guide: Simulation and Analysis B-2008.09 421 Chapter 15: Spectrum Analysis .FFT Analysis ■ Start and stop time point ■ Fundamental frequency ■ Window type ■ Number of sampling time points Using Windows in FFT Analysis One problem with spectrum analysis in circuit simulators is that the duration of the signals is finite, although adjustable. Applying the FFT method to finiteduration sequences can produce inadequate results. This occurs because DFT assumes periodic extensions, causing spectral leakage. The effect occurs when the finite duration of the signal does not result in a sequence that contains a whole number of periods. This is especially true when you use FFT to detect or estimate signals – that is, to detect weak signals in the presence of strong signals, or to resolve a cluster of equal-strength frequencies. In FFT analysis, windows are frequency-weighting functions, applied to the time-domain data, to reduce the spectral leakage associated with finiteduration time signals. Windows are smoothing functions, which peak in the middle frequencies, and decrease to zero at the edges. Windows reduce the effects of discontinuities, as a result of finite duration. Figure 57 shows the windows available in HSPICE or HSPICE RF. Table 56 on page 423 lists the common performance parameters, for FFT windows. Figure 57 422 FFT Windows HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 15: Spectrum Analysis .FFT Analysis The most important parameters in Table 56 are: ■ Highest side-lobe level (to reduce bias, the lower the better). ■ Worst-case processing loss (to increase detectability, the lower the better). Table 56 Window Weighting Characteristics in FFT Analysis Highest SideLobe (dB) SideLobe Roll-Off (dB/ octave) 3.0-dB WorstBandwidth Case (1.0/T) Process Loss (dB) Window Equation Rectangular W(n)=1, 0 ≤ n < NPa -13 -6 0.89 3.92 Bartlett W(n)=2n/(NP-1), 0 ≤n ≤(NP/2)-1 W(n)=2-2n/(NP-1), NP/2 ≤n < NP -27 -12 1.28 3.07 Hanning W(n)=0.5-0.5[cos(2πn/(NP-1))], 0 ≤n < NP -32 -18 1.44 3.18 Hamming W(n)=0.54-0.46[cos(2πn/(NP-1))], 0 ≤ν < NP -43 -6 1.30 3.10 Blackman W(n)=0.42323 -0.49755[cos(2πn/(NP-1))] +0.07922cos[cos(4πn/(NP-1))], 0 ≤n < NP -58 -18 1.68 3.47 BlackmanHarris W(n)=0.35875 -0.48829[cos(2πn/(NP-1))] +0.14128[cos(4πn/(NP-1))] -0.01168[cos(6πn/(NP-1))], 0 ≤n < NP -92 -6 1.90 3.85 Gaussian a=2.5 a=3.0 a=3.5 W(n)=exp[-0.5a2(NP/2-1-n)2/(NP)2], 0 ≤n ≤(NP/2)-1 -42 W(n)=exp[-0.5a2(n-NP/2)2/(NP)2], -55 NP/2 ≤n < NP -69 -6 -6 -6 1.33 1.55 1.79 3.14 3.40 3.73 HSPICE® User Guide: Simulation and Analysis B-2008.09 423 Chapter 15: Spectrum Analysis .FFT Analysis Table 56 Window Weighting Characteristics in FFT Analysis (Continued) Window Equation KaiserBessel a=2.0 a=2.5 a=3.0 a=3.5 W(n)=I0(x2)/I0(x1) x1=pa x2=x1*sqrt[1-(2(NP/2-1-n)/NP)2], 0 ≤n ≤(NP/2)-1 x2=x1*sqrt[1-(2(n-NP/2)/NP)2], NP/2 ≤n < NP I0 is the zero-order modified Bessel function Highest SideLobe (dB) SideLobe Roll-Off (dB/ octave) 3.0-dB WorstBandwidth Case (1.0/T) Process Loss (dB) -46 -57 -69 -82 -6 -6 -6 -6 1.43 1.57 1.71 0.89 3.20 3.38 3.56 3.74 a. NP is the number of points used for the FFT analysis. Some compromise usually is necessary, to find a suitable window filtering for each application. As a rule, window performance improves with functions of higher complexity (those listed lower in the table). ■ The Kaiser window has an ALFA parameter, which adjusts the compromise between different figures of merit for the window. ■ The simple rectangular window produces a simple bandpass truncation, in the classical Gibbs phenomenon. ■ The Bartlett or triangular window has good processing loss, and good sidelobe roll-off, but lacks sufficient bias reduction. ■ The Hanning, Hamming, Blackman, and Blackman-Harris windows use progressively more complicated cosine functions. These functions provide smooth truncation, and a wide range of side-lobe level and processing loss. ■ The last two windows in the table are parameterized windows. Use these windows to adjust the side-lobe level, the 3 dB bandwidth, and the processing loss. Figure 58 and Figure 59 show the characteristics of two typical windows. 424 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 15: Spectrum Analysis .FFT Analysis Figure 58 Bartlett Window Characteristics Figure 59 Kaiser-Bessel Window Characteristics, ALFA=3.0 HSPICE® User Guide: Simulation and Analysis B-2008.09 425 Chapter 15: Spectrum Analysis Examining the FFT Output Examining the FFT Output HSPICE or HSPICE RF prints FFT analysis results in tabular format, in the .lis file. These results are based on parameters in the .FFT statement. HSPICE prints normalized magnitude values, unless you specify FORMAT=UNORM, in which case it prints unnormalized magnitude values. The number of printed frequencies is half the number of points (NP) specified in the .FFT statement. ■ If you use FMIN to specify a minimum frequency, or FMAX to specify a maximum frequency, HSPICE or HSPICE RF prints only the specified frequency range. ■ If you use FREQ to specify a frequency, HSPICE or HSPICE RF outputs harmonics of this frequency, and the percent of total harmonic distortion. HSPICE or HSPICE RF generates a .ft# file and the listing file for each FFT output variable that contains data to display in FFT analysis waveforms (such as in WaveView Analyzer). You can view the magnitude in dB, and the phase in degrees. In the following sample FFT analysis .lis file output, the header defines parameters in the FFT analysis. ****** Sample FFT output extracted from the .lis file fft test ... sine ****** fft analysis tnom= 25.000 temp= 25.000 ****** fft components of transient response v(1) Window: Rectangular First Harmonic: 1.0000k Start Freq: 1.0000k Stop Freq: 10.0000k dc component: mag(db)= -1.132D+02 mag= 2.191D-06 phase= 1.800D+02 frequency frequency fft_mag fft_mag fft_phase index (hz) (db) (deg) 2 1.0000k 0. 1.0000 -3.8093m 4 2.0000k -125.5914 525.3264n -5.2406 6 3.0000k -106.3740 4.8007u -98.5448 8 4.0000k -113.5753 2.0952u -5.5966 10 5.0000k -112.6689 2.3257u -103.4041 12 6.0000k -118.3365 1.2111u 167.2651 14 7.0000k -109.8888 3.2030u -100.7151 16 8.0000k -117.4413 1.3426u 161.1255 18 9.0000k -97.5293 13.2903u 70.0515 20 10.0000k -114.3693 1.9122u -12.5492 total harmonic distortion = 1.5065m percent 426 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 15: Spectrum Analysis Examining the FFT Output The preceding example specifies a frequency of 1 kHz, and a THD up to 10 kHz, which corresponds to the first ten harmonics. The highest FFT output frequency might not match the specified FMAX, due to adjustments that HSPICE or HSPICE RF makes. Table 57 describes the output of the FFT analysis. Table 57 .FFT Output Description Column Heading Description Frequency Index Runs from 1 to NP/2, or the corresponding index for FMIN and FMAX. The DC component, corresponding to the 0 index, displays independently. Frequency The actual frequency, associated with the index. fft_mag (dB), fft_mag The first FFT magnitude column is in dB. The second FFT magnitude column is in units of the output variable. HSPICE or HSPICE RF normalizes the magnitude, unless you specify UNORM format. fft_phase Associated phase, in degrees. Notes: ■ Use the following formula as a guideline to specify a frequency range for FFT output: frequency increment = 1.0/(STOP - START) Each frequency index is a multiple of this increment. To obtain a finer frequency resolution, maximize the duration of the time window or specify more time points (larger NP). ■ FMIN and FMAX have no effect on the .ft0, .ft1, ..., .ftn files. ■ If FFTOUT is specified in a .OPTION statement, HSPICE can print results of THD, SNR, SFDR, SNDR, and ENOB and then sort the harmonics of fundamental by magnitude size. Assume that freq=f0 is the fundamental frequency. • THD is total harmonic distortion, which can be computed with the following formula: HSPICE® User Guide: Simulation and Analysis B-2008.09 427 Chapter 15: Spectrum Analysis Examining the FFT Output ( sum ( mag ( n ⋅ f 0 ) ⋅ mag ( n ⋅ f 0 ) ) ) THD = -------------------------------------------------------------------------------------------mag ( f 0 ) • SNR is the ratio of signal to noise, which can be computed with the following formula: ( mag ( f 0 ) ⋅ mag ( f 0 ) ) SNR = 10 log -------------------------------------------------------sum(mag ( f ) ⋅ mag ( f )) The f loop over the whole spectrum except f0 and its harmonics. If FMIN/ FMAX is specified, f loops over the spectrum between FMIN and FMAX except fo and its harmonics, as well as all the frequency components above FMAX. • SFDR is the spurious-free dynamic range and is defined as the distance from the fundamental input signal to the highest spur (in dB). SFDR involves both magnitude distance and frequency separation. • SNDR is the signal to noise and distortion ratio, which is the level of the fundamental divided by the square root of the sum of squares of all frequency components other than the fundamental frequency. It can be computed with the following formula: mag ( f 0 ) ⋅ mag ( f 0 ) SNDR = 10 log -------------------------------------------------------sum(mag ( f ) ⋅ mag ( f )) • ENOB is the effective number of bits, which can be computed with the following formula: ENOB = ( SNDR – 1.76db ) -----------------------------------------6.02 The f loops over the whole spectrum except f0. If FMIN/FMAX is specified, f loops over the spectrum between FMIN and FMAX except fo. All the frequency components above FMAX are also looped by f. Measuring FFT Output Information All of the FFT output information above can be measured using the following syntax: 428 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 15: Spectrum Analysis AM Modulation Measuring frequency component at certain frequency point: .MEASURE FFT result + Find [vm|vp|vr|vi|vdb|im|ip|ir|ii|idb](signal) AT=freq Measuring THD of a signal spectrum up to a certain harmonic: .MEASURE FFT result THD signal_name [NBHARM=num] Default: NBHARM=maximum harmonic in FFT result. Measuring SNR/SNDR/ENOB of a signal up to a certain frequency point: .MEASURE FFT result [SNR|SNDR|ENOB] signal_name + [NBHARM=num|MAXFREQ=val] Default: NBHARM=maximum harmonic in FFT result. All the frequency components above NBHARM are considered to be noise. MAXFREQ=maximum frequency in FFT result. All the frequency components above MAXFREQ are considered to be noise. Measuring SFDR of a signal from minfreq to maxfreq: .MEASURE FFT result SFDR signal_name [MAXFREQ=val][MINFREQ=val] Default: MINFREQ=0. MAXFREQ=Maximum frequency in FFT result. Syntax to perform FFT measurements from previous simulation results: hspice -i *.tr0 -meas measure_file For more information, see .MEASURE FFT in the HSPICE Reference Manual: Commands and Control Options. AM Modulation This example is based on demonstration netlist exam1.sp, which is available in directory \$installdir/demo/hspice/fft, shows a 1 kHz carrier (FC), which a 100 Hz signal (FM) modulates. HSPICE® User Guide: Simulation and Analysis B-2008.09 429 Chapter 15: Spectrum Analysis AM Modulation AM Modulation .OPTION post .PARAM sa=10 offset=1 fm=100 fc=1k td=1m VX 1 0 AM(sa offset fm fc td) Rx 1 0 1 .TRAN 2u 50m .FFT V(1) START=10m STOP=40m FMIN=833 FMAX=1.16K .END The following equation describes the voltage at node 1, which is an AM signal: v ( 1 ) = sa ⋅ ( offset + sin ( ωm ( Time – td ) ) ) ⋅ sin ( ωc ( Time – td ) ) You can expand the preceding equation, as follows. v ( 1 ) = ( sa ⋅ offset ⋅ sin ( ωc ( Time – td ) ) + 0.5 ⋅ sa ⋅ cos ( ( ωc – ωm ) ( Time – td ) ) ) – 0.5 ⋅ sa ⋅ cos ( ( ωc + ωm ) ( Time – td ) ) where ωc = 2 π f c ωf = 2 π f m The preceding equations indicate that v(1) is a summation of three signals, with the following frequency: f c , ( f c – f m ) , and ( f c + f m ) This is the carrier frequency and the two sidebands. See also Behavioral Amplitude Modulator on page 679. Graphical Output Figure 60 and Figure 61 on page 431 display the results. ■ Figure 60 shows the time-domain curve for node 1. ■ Figure 61 shows the frequency-domain components, for the magnitude of node 1. The carrier frequency is 1 kHz, with two sideband frequencies 100 Hz apart. 430 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 15: Spectrum Analysis AM Modulation The third, fifth, and seventh harmonics are more than 100 dB below the fundamental, indicating excellent numerical accuracy. The time-domain data contains an integer multiple of the period, so you do not need to use windowing. 19.8775 exam1.tr0 v(1 Volt [Lin] 10.0 0 -10.0 -19.877 0 10.0m 20.0m 30.0m 40.0m 50.0m Time [Lin] Figure 60 AM Modulation 0 exam1.ft0 vdb(1 -25.0 Volt [Lin] -50.0 -75.0 -100.0 -125.0 -150.0 0 2.0k 4.0k 6.0k 8.0k 10.0k Hertz [Lin] Figure 61 AM Modulation Spectrum HSPICE® User Guide: Simulation and Analysis B-2008.09 431 Chapter 15: Spectrum Analysis Balanced Modulator and Demodulator Balanced Modulator and Demodulator Demodulation, or detection, recovers a modulating signal from the modulated output voltage. The netlist, in the Input and Output Listing section that follows, shows this process. This example uses HSPICE or HSPICE RF behavioral models, and FFT analysis, to confirm the validity of the process, in the frequency domain. The low-pass filter uses the Laplace element. This filter introduces delay in the output signal, which causes spectral leakage if you do not use FFT windowing. However, if you use window weighting to perform FFT, you eliminate most of the spectral leakage. The THD of the two outputs, shown in “Input and Output Listing,” verifies this. HSPICE or HSPICE RF expects a 1 kHz output signal, so specify a 1 kHz frequency in the .FFT command. Also specify FMAX, to provide the first few harmonics in the output listing, for THD calculations. Input and Output Listing The sample input and output listing files are located in the following directory: \$installdir/demo/hspice/fft/balance.sp Figure 62 through Figure 70 show the signals, and their spectral content. The modulated signal contains only the sum, and the difference of the carrier frequency and the modulating signal (1 kHz and 10 kHz). At the receiver end, this example recovers the carrier frequency, in the demodulated signal. This example also shows a 10 kHz frequency shift, in the above signals (to 19 kHz and 21 kHz). A low-pass filter uses a second-order Butterworth filter, to extract the carrier frequency. A Harris window significantly improves the noise floor in the filtered output spectrum, and reduces THD in the output listing (from 9.23% to 0.047%). However, this example needs a filter with a steeper transition region, and better delay characteristics, to suppress modulating frequencies below -60 dB. Figure 65 is a normalized filtered output signal waveform. 432 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 15: Spectrum Analysis Balanced Modulator and Demodulator exam2.ft0 v(mod1 2.0 Volt [Lin] 4.0 v(mod2 0 -2.0 -4.0 0 1.0m 2.0m 3.0m 4.0m Time [Lin] Figure 62 Modulating and Modulated Signals exam2.ft0 v(modout 2.0 Volt [Lin] 1.0 0 -1.0 -2.0 0 1.0m 2.0m 3.0m 4.0m Time [Lin] Figure 63 Modulated Signal HSPICE® User Guide: Simulation and Analysis B-2008.09 433 Chapter 15: Spectrum Analysis Balanced Modulator and Demodulator exam2.tr0 v(demod 1.0 Volt [Lin] 500.0m 0 -500.0 -1.0 0 1.0m 2.0m 3.0m 4.0m Time [Lin] Figure 64 Demodulated Signal 1.0 exam2.tr0 v(lpout Volt [Lin] 500.0m 0 -500.0 -1.0 0 1.0m 2.0m 3.0m 4.0m Time [Lin] Figure 65 434 Filtered Output Signal HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 15: Spectrum Analysis Balanced Modulator and Demodulator 0 exam2.ft0 vdb(mod1 Volt [Lin] -50.0 exam2.ft1 vdb(mod2 -100.0 -150.0 -200.0 0 10.0k 20.0k 30.0k 40.0k 50.0k Hertz [Lin] Figure 66 Modulating and Modulated Signal Spectrum 0 exam2.ft2 vdb(modout Volt [Lin] -50.0 -100.0 -150.0 -187.82 0 10.0k 20.0k 30.0k 40.0k 50.0k Hertz [Lin] Figure 67 Modulated Signal Spectrum HSPICE® User Guide: Simulation and Analysis B-2008.09 435 Chapter 15: Spectrum Analysis Balanced Modulator and Demodulator 0 exam2.ft3 vdb(demod Volt [Lin] -50.0 -100.0 -150.0 -200.0 0 10.0k 20.0k 30.0k 40.0k 50.0k Hertz [Lin] Figure 68 Demodulated Signal Spectrum 0 exam2.ft4 vdb(1pout -10.0 Volt [Lin] -20.0 -30.0 -40.0 -50.0 -60.0 0 10.0k 20.0k 30.0k 40.0k 50.0k Hertz [Lin] Figure 69 436 Filtered Output Signal (no window) HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 15: Spectrum Analysis Signal Detection Test Circuit 0 exam2.ft5 vdb(1pout -25.0 Volt [Lin] -50.0 -75.0 -100.0 -125.0 -150.0 0 10.0k 20.0k 30.0k 40.0k 50.0k Hertz [Lin] Figure 70 Filtered Output Signal (Blackman-Harris window) Signal Detection Test Circuit This example is a high-frequency mixer test circuit. It illustrates the effect of using a window to detect a weak signal, in the presence of a strong signal that is at a nearby frequency. This example adds two high-frequency signals, with a 40 dB separation (amplitudes are 1.0 and 0.01). Input Listing The sample input listing file is located in the following directory: \$installdir/demo/hspice/fft/exam3.sp Output Figure 71 shows the rectangular window. Compare this with the spectra of the output for all FFT window types, as shown in Figure 72 through Figure 78. Without windowing, HSPICE or HSPICE RF does not detect the weak signal because of spectral leakage. HSPICE® User Guide: Simulation and Analysis B-2008.09 437 Chapter 15: Spectrum Analysis Signal Detection Test Circuit 0 exam3.ft0 vdb(3 -10.0 Volt [Lin] -20.0 -30.0 -40.0 -50.0 -60.0 0 1.0g 2.0g 3.0g 4.0g 5.0g Hertz [Lin] Figure 71 Mixer Output Spectrum, Rectangular Window ■ In the Bartlett window (Figure 72), the noise floor increases dramatically, compared to the rectangular window (from -55, to more than -90 dB). ■ The cosine windows (Hanning, Hamming, Blackman, and Blackman-Harris) all produce better results than the Bartlett window. However, the BlackmanHarris window provides the highest degree of separation for the two tones, and the lowest noise floor. ■ The final two windows (Figure 77 and Figure 78) use the ALFA=3.0 parameter, which is the default value in HSPICE or HSPICE RF. These two windows also produce acceptable results, especially the Kaiser-Bessel window, which sharply separates the two tones, and has a noise floor of almost -100-dB. Processing such high frequencies, as demonstrated in this example, shows the numerical stability and accuracy of the FFT spectrum analysis algorithms, in HSPICE or HSPICE RF. 438 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 15: Spectrum Analysis Signal Detection Test Circuit 0 exam3.ft1 vdb(3 -20.0 Volt [Lin] -40.0 -60.0 -80.0 -100.0 -120.0 0 1.0g 2.0g 3.0g 4.0g 5.0g Hertz [Lin] Figure 72 Mixer Output Spectrum, Bartlett Window 0 exam3.ft2 vdb(3 -20.0 Volt [Lin] -40.0 -60.0 -80.0 -100.0 -120.0 0 1.0g 2.0g 3.0g 4.0g 5.0g Hertz [Lin] Figure 73 Mixer Output Spectrum, Hanning Window HSPICE® User Guide: Simulation and Analysis B-2008.09 439 Chapter 15: Spectrum Analysis Signal Detection Test Circuit 0 exam3.ft3 vdb(3 Volt [Lin] -20.0 -40.0 -60.0 -80.0 0 1.0g 2.0g 3.0g 4.0g 5.0g Hertz [Lin] Figure 74 Mixer Output Spectrum, Hamming Window 0 exam3.ft4 vdb(3 -20.0 Volt [Lin] -40.0 -60.0 -80.0 -100.0 -120.0 0 1.0g 2.0g 3.0g 4.0g 5.0g Hertz [Lin] Figure 75 440 Mixer Output Spectrum, Blackman Window HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 15: Spectrum Analysis Signal Detection Test Circuit 0 exam3.ft5 vdb(3 -20.0 Volt [Lin] -40.0 -60.0 -80.0 -100.0 -120.0 0 1.0g 2.0g 3.0g 4.0g 5.0g Hertz [Lin] Figure 76 Mixer Output Spectrum, Blackman-Harris Window 0 exam3.ft6 vdb(3 -20.0 Volt [Lin] -40.0 -60.0 -80.0 -100.0 0 1.0g 2.0g 3.0g 4.0g 5.0g Hertz [Lin] Figure 77 Mixer Output Spectrum, Gaussian Window HSPICE® User Guide: Simulation and Analysis B-2008.09 441 Chapter 15: Spectrum Analysis Signal Detection Test Circuit 0 exam3.ft7 vdb(3 -20.0 Volt [Lin] -40.0 -60.0 -80.0 -100.0 -120.0 0 1.0g 2.0g 3.0g 4.0g 5.0g Hertz [Lin] Figure 78 442 Mixer Output Spectrum, Kaiser-Bessel Window HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 15: Spectrum Analysis References References [1] For an excellent discussion of DFT windows, see Fredric J. Harris, “On the Use of Windows for Harmonic Analysis with Discrete Fourier Transform,” Proceedings of the IEEE, Vol. 66, No. 1, Jan. 1978. HSPICE® User Guide: Simulation and Analysis B-2008.09 443 Chapter 15: Spectrum Analysis References 444 HSPICE® User Guide: Simulation and Analysis B-2008.09 16 16 AC Small-Signal and Noise Analysis Describes how to perform AC and noise small signal analyses in HSPICE. This chapter covers AC small signal analysis, AC analysis of an RC network, noise analysis, and other AC analysis statements. For information on output variables, see AC Analysis Output Variables on page 310. For descriptions of individual HSPICE commands referenced in this chapter, see Chapter 2, HSPICE and HSPICE RF Netlist Commands in the HSPICE Reference Manual: Commands and Control Options. These topics are covered in the following sections: ■ Using the .AC Statement ■ AC Small Signal Analysis ■ AC Analysis of an RC Network ■ Using .NOISE for Small-Signal Noise Analysis ■ Other AC Analysis Statements Using the .AC Statement You can use the .AC statement for the following applications: ■ Single/double sweeps ■ Sweeps using parameters ■ .AC analysis optimization ■ Random/Monte Carlo analyses For .AC command syntax, see the .AC command in the HSPICE Reference Manual: Commands and Control Options. HSPICE® User Guide: Simulation and Analysis B-2008.09 445 Chapter 16: AC Small-Signal and Noise Analysis Using the .AC Statement .AC Control Options You can use the following .AC control options when performing an AC analysis: ABSH ACOUT DI MAXAMP RELH UNWRAP For syntax descriptions for these options, see Chapter 3, HSPICE and RF Netlist Simulation Control Options in the HSPICE Reference Manual: Commands and Control Options. .AC Command Examples Example 1 .AC DEC 10 1K 100MEG This example performs a frequency sweep by 10 points per decade from 1kHz to 100MHz. Example 2 .AC LIN 100 1 100HZ This example runs a 100-point frequency sweep from 1- to 100-Hz. Example 3 .AC DEC 10 1 10K SWEEP cload LIN 20 1pf 10pf This example performs an AC analysis for each value of cload. This results from a linear sweep of cload between 1- and 10-pF (20 points), sweeping the frequency by 10 points per decade from 1- to 10-kHz. Example 4 .AC DEC 10 1 10K SWEEP rx POI 2 5k 15k This example performs an AC analysis for each value of rx, 5k and 15k, sweeping the frequency by 10 points per decade from 1- to 10-kHz. Example 5 .AC DEC 10 1 10K SWEEP DATA=datanm This example uses the .DATA statement to perform a series of AC analyses, modifying more than one parameter. The datanm file contains the parameters. 446 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 16: AC Small-Signal and Noise Analysis AC Small Signal Analysis Example 6 .AC DEC 10 1 10K SWEEP MONTE=30 This example illustrates a frequency sweep and a Monte Carlo analysis with 30 trials. Example 7 AC DEC 10 1 10K SWEEP MONTE=10 firstrun=15 This example illustrates a frequency sweep and a Monte Carlo analysis from the 15th to the 24th trials. Example 8 .AC DEC 10 1 10K SWEEP MONTE=list(10 20:30 35:40 50) This example illustrates a frequency sweep and a Monte Carlo analysis at 10th trial and then from the 20th to 30th trial, followed by the 35th to 40th trial and finally at 50th trial. AC Small Signal Analysis AC small signal analysis in HSPICE computes AC output variables as a function of frequency (see Figure 79 on page 448). HSPICE first solves for the DC operating point conditions. It then uses these conditions to develop linear, small-signal models for all non-linear devices in the circuit. HSPICE® User Guide: Simulation and Analysis B-2008.09 447 Chapter 16: AC Small-Signal and Noise Analysis AC Small Signal Analysis Simulation Experiment DC Transient AC AC Small-Signal Simulations .AC .NOISE .DISTO .SAMPLE .LIN .NET AC options: ABSH ACOUT DI MAXAMP RELH UNWRAP Figure 79 DC options, to solve operating-point AC Small Signal Analysis Flow In HSPICE, the output of AC Analysis includes voltages and currents. HSPICE converts capacitor and inductor values to their corresponding admittances: y C = j ωC for capacitors 1y L = ------- for inductors j ωL Resistors can have different DC and AC values. If you specify AC=<value> in a resistor statement, HSPICE uses the DC value of resistance to calculate the operating point, but uses the AC resistance value in the AC analysis. When you analyze operational amplifiers, HSPICE uses a low value for the feedback resistance to compute the operating point for the unity gain configuration. You can then use a very large value for the AC resistance in AC analysis of the open loop configuration. AC analysis of bipolar transistors is based on the small-signal equivalent circuit, as described in the HSPICE Elements and Device Models Manual. MOSFET 448 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 16: AC Small-Signal and Noise Analysis AC Analysis of an RC Network AC-equivalent circuit models are described in the HSPICE Elements and Device Models Manual. The AC analysis statement can sweep values for: ■ Frequency. ■ Element. ■ Temperature. ■ Model parameter. ■ Randomized (Monte Carlo) distribution. ■ Optimization and AC analysis. Additionally, as part of the small-signal analysis tools, HSPICE provides: ■ Noise analysis. ■ Distortion analysis. ■ Network analysis. ■ Sampling noise. You can use the .AC statement in several different formats, depending on the application. You can also use the .AC statement to perform data-driven analysis in HSPICE. AC Analysis of an RC Network Figure 80 on page 450 shows a simple RC network with a DC and AC source applied. The circuit consists of: ■ Two resistors, R1 and R2. ■ Capacitor C1. ■ Voltage source V1. ■ Node 1 is the connection between the source positive terminal and R1. ■ Node 2 is where R1, R2, and C1 are connected. ■ HSPICE ground is always node 0. HSPICE® User Guide: Simulation and Analysis B-2008.09 449 Chapter 16: AC Small-Signal and Noise Analysis AC Analysis of an RC Network 1 R1 1k V1 10 VDC 1VAC 2 + _ R2 1k C1 0.001uF 0 Figure 80 RC Network Circuit The netlist for this RC network is based on demonstration netlist quickAC.sp, which is available in directory \$<installdir>/demo/hspice/apps: A SIMPLE AC RUN .OPTION LIST NODE POST .OP .AC DEC 10 1K 1MEG .PRINT AC V(1) V(2) I(R2) I(C1) V1 1 0 10 AC 1 R1 1 2 1K R2 2 0 1K C1 2 0 .001U .END Follow this procedure to perform AC analysis for an RC network circuit. 1. Type the above netlist into a file named quickAC.sp. 2. To run a HSPICE analysis, type: hspice quickAC.sp > quickAC.lis When the run finishes, HSPICE displays: >info: ***** hspice job concluded This is followed by a line that shows the amount of real time, user time, and system time needed for the analysis. Your run directory includes the following new files: • 450 quickAC.ac0 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 16: AC Small-Signal and Noise Analysis AC Analysis of an RC Network • quickAC.ic0 • quickAC.lis • quickAC.st0 3. Use an editor to view the .lis and .st0 files to examine the simulation results and status. 4. Run WaveView. 5. From the File menu, select File > Import > Waveform File. 6. Select the quickAC.ac0 file from the Open: Waveform Files window. 7. Display the voltage at node 2 by using a log scale on the x-axis. Figure 81 on page 451 shows the waveform that HSPICE produces if you sweep the response of node 2, as you vary the frequency of the input from 1 kHz to 1 MHz. Figure 81 RC Network Node 2 Frequency Response As you sweep the input from 1 kHz to 1 MHz, the quickAC.lis file displays: ■ Input netlist. ■ Details about the elements and topology. HSPICE® User Guide: Simulation and Analysis B-2008.09 451 Chapter 16: AC Small-Signal and Noise Analysis Using .NOISE for Small-Signal Noise Analysis ■ Operating point information. ■ Table of requested data. The quickAC.ic0 file contains information about DC operating point conditions. The quickAC.st0 file contains information about the simulation run status. To use the operating point conditions for subsequent simulation runs, execute the .LOAD statement. Using .NOISE for Small-Signal Noise Analysis A circuit noise analysis can be performed associated with a small-signal .AC analysis. The .NOISE command will activate a noise analysis that calculates the output noise generated based on the contributions from all noise sources within the circuit. This noise may be from passive elements, such as thermal (Johnson) noise in resistors, or from sources such as shot, channel, and flicker noise present within transistors. Most transistors will have several noise sources. For descriptions of noise models for each device type, see the HSPICE Reference Manual: Elements and Device Models. In most cases, the individual noise sources in HSPICE lack statistical correlation, and this allows their contributions to output noise to be computed independently. The total output noise voltage is the RMS sum of the individual noise contributions: N onoise = ∑ Zk 2 i nk 2 k=0 Where, onoise is the output noise spectral density ( V ⁄ Hz ) at the AC analysis frequency. 2 2 i nk is the mean-squared noise spectral density ( A ⁄ Hz ) for each noise current source due to thermal, shot, flicker, or other noise. Z k is the equivalent transimpedance between each noise current source and the output. N is the number of noise sources associated with all circuit elements. This analysis will be performed for every frequency specified with the .AC command. The output for noise analysis is specified in the .NOISE syntax: 452 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 16: AC Small-Signal and Noise Analysis Using .NOISE for Small-Signal Noise Analysis Basic Syntax: .NOISE v(out <,ref>) src <interval> The output noise (onoise) voltage is computed at the out node specified; if the (optional) ref node is also given, the output is taken as the differential output noise voltage v(out,ref). Noise analysis requires the specification of an independent input source (src). This allows the calculation of the equivalent input noise given by inoise = onoise ---------------G Where, inoise is the equivalent input noise spectral density at the input source. G is the gain between the input source (src) and the output. The .NOISE analysis can also generate a summary for how each noise generator within the circuit will contribute to output noise. Specify an integer value for interval to include a device noise summary for every interval frequency points in the HSPICE output listing. No summary is included unless interval is specified. The .NOISE analysis will also compute the total integrated noise over the AC frequency range, which will also be included in the output listing. The output summary will include values for the device noise sources given in Table 58 on page 454 — Table 60 on page 455. To request .NOISE analysis results (magnitude and decibel) with .print/ .probe use: .probe noise onoise onoise(m) onoise(db) .probe noise inoise inoise(m) inoise(db) Results will be included in the *.ac0 file. Output noise voltage or current units are either V ⁄ Hz or A ⁄ Hz , respectively. Device-level noise source contributions will also be included in the *.ac0 file (unless you have set .option probe=1). The naming convention and units for device level noise contributions is also shown in the following tables. To ensure that device noise models will be included in the analysis, verify that noise parameters are being set in your transistor models. Include values for AF and KF, for example, if you wish to activate flicker noise models for your devices. See also, Using Noise Analysis Results as Input Noise Sources in the HSPICE User Guide: RF Analysis. HSPICE® User Guide: Simulation and Analysis B-2008.09 453 Chapter 16: AC Small-Signal and Noise Analysis Using .NOISE for Small-Signal Noise Analysis For a complete description of the .NOISE command syntax and examples, see the .NOISE command in the HSPICE Reference Manual: Commands and Control Options. Note that the .NOISE analysis requires an .AC statement, and that if more than one .NOISE statement is included, HSPICE will run only the last statement. Table 58 .NOISE Measurements Available for MOSFETs .ac .lis Unit Description nd rd 2 V -----Hz Output thermal noise due to drain resistor ns rs 2 V -----Hz Output thermal noise due to source resistor ni id 2 V -----Hz Output channel thermal noise nf fn 2 V -----Hz Output flicker noise ntg total 2 V -----Hz Total output noise: Table 59 TOT=RD + RS + ID + FN .NOISE Measurements Available for BJTs .ac Unit Description rb rb 2 V -----Hz Output thermal noise due to base resistor rc rc 2 V -----Hz Output thermal noise due to collector resistor re 454 .lis re 2 V -----Hz Output thermal noise due to emitter resistor HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 16: AC Small-Signal and Noise Analysis Other AC Analysis Statements Table 59 .NOISE Measurements Available for BJTs (Continued) .ac .lis Unit Description nb ib 2 V -----Hz Output noise due to base shot noise source nc ic 2 V -----Hz Output thermal noise due to collector shot noise source nf fn 2 V -----Hz Output noise due to flicker noise source nt total 2 V -----Hz Total output noise: Table 60 TOT=RB + RC + RE + IB + IC + FN .NOISE Measurements Available for Diodes .ac .lis Unit Description nr rs 2 V -----Hz Output noise due to diode series resistance ni id 2 V -----Hz Output noise due to shot noise nf fn 2 V -----Hz Output noise due to flicker noise nt total 2 V -----Hz Total output noise: TOT=RS + ID + FN Other AC Analysis Statements The following sections describe the commands you can use to perform other types of AC analyses: HSPICE® User Guide: Simulation and Analysis B-2008.09 455 Chapter 16: AC Small-Signal and Noise Analysis Other AC Analysis Statements ■ Using .DISTO for Small-Signal Distortion Analysis on page 456 ■ Using .SAMPLE for Noise Folding Analysis on page 456 Use the .NOISE and .AC statements to control the noise analysis of the circuit. Using .DISTO for Small-Signal Distortion Analysis The .DISTO statement computes the distortion characteristics of the circuit in an AC small-signal, sinusoidal, steady-state analysis. HSPICE computes and reports five distortion measures at the specified load resistor. The analysis is performed assuming that one or two signal frequencies are imposed at the input. The first frequency, F1 (used to calculate harmonic distortion), is the nominal analysis frequency set by the .AC statement frequency sweep. The optional second input frequency, F2 (used to calculate intermodulation distortion), is set implicitly by specifying the skw2 parameter, which is the ratio F2/F1. For command syntax and examples, see the .DISTO command in the HSPICE Reference Manual: Commands and Control Options. Using .SAMPLE for Noise Folding Analysis For data acquisition of analog signals, data sampling noise often needs to be analyzed. This is accomplished with the .SAMPLE statement used in conjunction with the .NOISE and .AC statements. The SAMPLE analysis performs a simple noise folding analysis at the output node. For the syntax and description of the .SAMPLE statement, see the .SAMPLE command in the HSPICE Reference Manual: Commands and Control Options. 456 HSPICE® User Guide: Simulation and Analysis B-2008.09 17 17 Linear Network Parameter Analysis Describes how to perform an AC sweep to extract small-signal linear network parameters in HSPICE and HSPICE RF. The chapter covers .LIN analysis, RF measurements from .LIN, extracting mixed-mode S (scattering) and noise parameters, and additional measurements. For descriptions of individual commands referenced in this chapter, see the HSPICE Reference Manual: Commands and Control Options. These topics are covered in the following sections: ■ .LIN Analysis ■ Additional Measurements From .LIN ■ Extracting Mixed-Mode Scattering (S) Parameters .LIN Analysis The .LIN command extracts noise and linear transfer parameters for a general multi-port network. When used with the .AC command, .LIN makes available a broad set of linear port-wise measurements: ■ Multi-port scattering [S] parameters ■ Noise parameters ■ Stability factors ■ Gain factors ■ Matching coefficients HSPICE® User Guide: Simulation and Analysis B-2008.09 457 Chapter 17: Linear Network Parameter Analysis .LIN Analysis The .LIN analysis is similar to basic small-signal, swept-frequency .AC analysis, but it also automatically calculates a series of noise and small-signal transfer parameters between the terminals identified using port (P) elements. HSPICE can output the result of group delay extraction and two-port noise analysis to either a .sc* file, a Touchstone file, or a CITIfile. The .PRINT/.PROBE/.MEAS output syntax for .LIN supports H (hybrid) parameters and S/Y/Z/H group delay. I1 Z01 Figure 82 P1 I2 + V1 - Circuit under test + V2 P2 Z02 - Basic Circuit in .LIN Analysis Identifying Ports with the P-element The .LIN command computes the S (scattering), Y (admittance), and Z (impedance) parameters directly based on the location of the port (P) elements in your circuit, and the specified values for their reference impedances. The port element identifies the ports used in .LIN analysis. A full description of the port element and syntax may be found in the Port Element section of the chapter on Sources and Stimuli in this user guide. Using the P-element for Mixed-Mode Measurement You can use a port element with three terminals as the port element for measuring the mixed mode S-parameters. Except for the number of external terminals, the syntax of the port element remains the same. The .LIN analysis function internally sets the necessary drive mode (common/differential) of these mixed mode port elements. For analyses other than the .LIN analysis (such as DC, AC, TRAN, and so on), the mixed-mode P-element acts as a differential driver that drives positive nodes with half of their specified voltage 458 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 17: Linear Network Parameter Analysis .LIN Analysis and the negative nodes with a negated half of the specified voltage. Figure 83 shows the block diagram of the mixed mode port element. P1 (port element) n1+ Zo Zo V+ Vn1- n1_ref P1 n1+ n1- n1_ref Zo=50 Figure 83 Mixed Mode Port Element The port element can also be used as a signal source with a built in reference impedance. For further information on its use as a signal source, see Chapter 9, Sources and Stimuli. .LIN Input Syntax .LIN [sparcalc=1|0 [modelname = modelname]] + [filename = filename] [format=selem|citi|touchstone] + [noisecalc=1|0] [gdcalc=1|0] + [mixedmode2port=dd|dc|ds|cd|cc|cs|sd|sc|ss] + [dataformat=ri|ma|db] + [listfreq=(frequencies|none|all)] + [listcount=num] [listfloor=val] [listsources=1|0|on|off] For argument descriptions, see the .LIN command in the HSPICE Reference Manual: Commands and Control Options. .LIN Output Syntax This section describes the syntax for the .PRINT and .PROBE statements used for LIN analysis. HSPICE® User Guide: Simulation and Analysis B-2008.09 459 Chapter 17: Linear Network Parameter Analysis .LIN Analysis .PRINT and .PROBE Statements .PRINT AC Xmn | Xmn LINPARAM(TYPE) | X(m,n) | + X(m,n) LINPARAM(TYPE)> Hmn | Hmn(TYPE) | + H(m,n) | H(m,n)(TYPE)> .PROBE AC Xmn | Xmn LINPARAM(TYPE) | X(m,n) | + X(m,n) LINPARAM(TYPE)> Hmn | Hmn(TYPE) | + H(m,n) | H(m,n)(TYPE)> Argument Description Xmn, X(m,n) One of these parameter types: ■ S (scattering parameters) Y (admittance parameters) ■ Z (impedance parameters) ■ H (hybrid parameters) mn refers to a pair of port numbers, where m can be 1 or 2, and n can be 1 or 2. ■ Hmn, H(m,n) Complex hybrid (H-) parameters. mn refers to a pair of port numbers, where m can be 1 or 2, and n can be 1 or 2. If m,n=0 or m,n>2, HSPICE issues a warning and ignores the output request. ■ To calculate a one-port H parameter, you must specify at least one port (P) element. ■ To calculate a two-port H parameter, you must specify two or more port (P) elements. For additional information, see Hybrid Parameter Calculations on page 462. 460 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 17: Linear Network Parameter Analysis .LIN Analysis Argument Description LINPARAM Two-port noise parameters: ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ NFMIN (noise figure minimum) NF (Noise figure) VN2 (Equivalent input noise voltage squared IN2 (Equivalent input noise current squared) RHON (Correlation coefficient between input noise voltage and input noise current) RN (Noise equivalent resistance) GN (Noise equivalent conductance) ZCOR (Noise correlation impedance) YCOR (Noise correlation admittance) ZOPT (Optimum source impedance for noise) YOPT (Optimum source admittance for noise) GAMMA_OPT (source reflection coefficient that achieves the minimum noise figure) ZOPT (source impedance that achieves minimum noise) RN (noise equivalent resistance) K_STABILITY_FACTOR (Rollett stability factor) MU_STABILITY_FACTOR (Edwards & Sinsky stability factor) G_MAX (maximum available/operating power gain) G_MSG (Maximum stable gain) G_TUMAX (Maximum unilateral transducer power gain) G_U (Unilateral power gain) G_MAX_GAMMA1 (source reflection coefficient that achieves maximum available power gain) G_MAX_GAMMA2 (load reflection coefficient that achieves maximum operating power gain) G_MAX_Z1=Source impedance needed to realize G_MAX (complex, Ohms) G_MAX_Z2=Load impedance needed to realize G_MAX (complex, Ohms) G_MAX_Y1=Source admittance needed to realize G_MAX (complex, Siemens) G_MAX_Y2=Load admittance needed to realize G_MAX (complex, Siemens) G_AS (associate gain—maximum gain at the minimum noise figure) VSWR(n) (voltage standing-wave ratio at the n port) GD (group delay from port=1 to port=2) G_MSG (maximum stable gain) G_TUMAX (maximum unilateral transducer power gain) G_U (unilateral power gain) HSPICE® User Guide: Simulation and Analysis B-2008.09 461 Chapter 17: Linear Network Parameter Analysis .LIN Analysis Argument Description TYPE Data type definitions: ■ ■ ■ ■ ■ ■ R=Real I=Imaginary M=Magnitude P=PD=Phase in degrees PR=Phase in radians DB=decibels Examples .print AC S11 S21(DB) S(2,3)(D) S(2,1)(I) .print AC NFMIN GAMMA_OPT G_AS .probe AC RN G_MAX ZOPT Y(3,1)(M) Y31(P) Hybrid Parameter Calculations The hybrid parameters are transformed from S-parameters: ■ For a one-port circuit, the calculation is: ( 1 + S 11 ) H 11 = Z 01 --------------------( 1 – S 11 ) ■ For a two-port circuit, the calculation is: ( 1 + S 11 ) ( 1 + S n ) – S 12 S 21 H 11 = Z 01 --------------------------------------------------------------( 1 – S 11 ) ( 1 + S n ) + S 12 S 21 H 12 = 2 S 12 Z 02 ------- ----------------------------------------------------------------Z 01 ( 1 – S 11 ) ( 1 + S 22 ) + S 12 S 21 H 21 = – S 21 Z 02 ------- ----------------------------------------------------------------Z 01 ( 1 – S 11 ) ( 1 + S 22 ) + S 12 S 21 1 - ( 1 – S 11 ) ( 1 S 22 ) – S 12 S 21H 22 = ------- ----------------------------------------------------------------Z 02 ( 1 – S 11 ) ( 1 + S 22 ) + S 12 S 21 For networks with more than two ports when computing the 1,2 H index parameters, HSPICE assumes that ports numbered 3 and above terminate in their port reference impedance (z0). The above two-port calculations therefore remain appropriate because S11, S12, S21, and S22 remain valid, and simulation can ignore higher order S-parameters. 462 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 17: Linear Network Parameter Analysis .LIN Analysis Multi-Port Scattering (S) Parameters S-parameters represent the ratio of incident and scattered (or forward and reflected) normalized voltage waves. Figure 84 shows a two-port network. I1 Port=1 Figure 84 Z01 I2 + V1 Two-Port Network - + V2 Z02 Port=2 - Two-Port Network The following equations define the incident (forward) waves for this two-port network: v 1 + Z 01 I 1 a 1 = ----------------------2 ⋅ Z 01 v 2 + Z 02 I 2 a 2 = ----------------------2 ⋅ Z 02 The following equations define the scattered (reflected) waves for this two-port network: v 1 – Z 01 I 1 b 1 = ----------------------2 ⋅ Z 01 v 2 – Z 02 I 2 b 2 = ----------------------2 ⋅ Z 02 The following equations define the S-parameters: b1 S 11 = ---a1 a2 = 0 b1 S 12 = ---a2 a1 = 0 b2 S 21 = ---a1 a2 = 0 b2 S 22 = ---a2 a1 = 0 Each S-parameter is a complex number, which can represent gain, isolation, or a reflection coefficient. Example The following examples show how you can represent a gain, isolation, or reflection coefficient: HSPICE® User Guide: Simulation and Analysis B-2008.09 463 Chapter 17: Linear Network Parameter Analysis .LIN Analysis .PRINT .PRINT .PRINT .PRINT AC AC AC AC S11(DB) S21(DB) S12(DB) S22(DB) \$ \$ \$ \$ Input return loss Gain Isolation Output return loss Two-Port Transfer and Noise Calculations Two-port noise analysis is a linear AC noise analysis method that determines the noise figure of a linear two-port for an arbitrary source impedance. Several output parameter measurements are specific to two-port networks. .LIN analysis supports two-port calculations for 3 or more ports if port=1 is the input and port=2 the output. All other ports terminate in their characteristic impedance. This is equivalent to operating on the two-port [S] submatrix extracted from the multi-port [S] matrix. This occurs for both signal and noise calculations. A warning appears if N<2 and you specified two-port quantities. Noise and signal port-wise calculations do not require that port elements use a ground reference. You can therefore measure fully-differential circuits. .LIN generates a set of noise parameters. The analysis assumes a noise model consisting of: ■ A shunt current noise source, called In, at the input of a noiseless two-port linear network. ■ A series voltage noise source, called Vn, at the input of a noiseless two-port linear network. ■ A source with impedance, called Zs, that drives this two-port network. ■ The two-port network drives a noiseless load, called Zl. Equivalent Input Noise Voltage and Current For each analysis frequency, HSPICE computes a noise equivalent circuit for a linear two-port. The noise equivalent circuit calculation results in an equivalent noise voltage and current, and their correlation coefficient. ■ ■ IN2: Equivalent input noise current squared (Real, A2). ■ 464 VN2: Equivalent input noise voltage squared (Real, V2). RHON: Correlation coefficient between the input noise voltage and the input noise current (complex, unitless). HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 17: Linear Network Parameter Analysis .LIN Analysis Equivalent Noise Resistance and Conductance These measurements are the equivalent resistance and conductance, which generate the equivalent noise voltage and current values at a temperature of T=290K in a 1Hz bandwidth. ■ RN: Noise equivalent resistance (Real, Ohms) ■ GN: Noise equivalent conductance (Real, Siemens) Noise Correlation Impedance and Admittance These measurements represent the equivalent impedance and admittance that you can insert at the input of the noise equivalent circuit to account for the correlation between the equivalent noise voltage and the current values. ■ ZCOR: Noise correlation impedance (Complex, Ohms) ■ YCOR: Noise correlation admittance (Complex, Siemens) Optimum Matching for Noise These measurements represent the optimum impedance, admittance, and reflection coefficient value that result in the best noise performance (minimum noise figure). ■ ZOPT: Optimum source impedance for noise (Complex, Ohms) ■ YOPT: Optimum source admittance for noise (Complex, Siemens) ■ GAMMA_OPT: Optimum source reflection coefficient (Complex, unitless) Because ZOPT and YOPT can commonly take on infinite values when computing optimum noise conditions, calculations for optimum noise loading reflect the GAMMA_OPT coefficient. Noise Figure and Minimum Noise Figure Noise figure represents the ratio of the SNR (signal to noise ratio) at the input to the SNR at the output. You can set the input source impedance to ZOPT to obtain the minimum noise figure. ■ NFMIN: Minimum noise figure (source at ZOPT) (real, unitless, power ratio) ■ NF: Noise figure (value obtained with source impedance at Zc[1]) (real, unitless, power ratio) HSPICE® User Guide: Simulation and Analysis B-2008.09 465 Chapter 17: Linear Network Parameter Analysis .LIN Analysis Associated Gain This measurement assumes that the input impedance matches the minimum noise figure, and the output matches the maximum gain. G_AS is the associated gain—maximum power gain at NFMIN (real, power ratio) Output Format for Group Delay in .sc* Files All of the S/Y/Z/H parameters support a group delay calculation. The output syntax of .PRINT and .PROBE statement for group delay is: Xmn(T) | Xmn(TD) | X(m,n)(T) | X(m,n)(TD) ■ X=S, Y, Z, or H ■ m, n=port number (1 or 2 for H parameter) The output of group delay matrices in .sc* files lets HSPICE directly read back the group delay information, the tabulated data uses the regular HSPICE model syntax with the SP keyword: *| group delay parameters .MODEL SMODEL_GD SP N=2 SPACING=POI INTERPOLATION=LINEAR + MATRIX=NONSYMMETRIC VALTYPE=REAL + DATA=3 + 1e+08 + 0 5e-09 + 5e-09 0 + {...data...} model name is the model name of the S-parameters, plus _GD. GROUPDELAY=[0|1] in the top line indicates group delay data: *| N=2 DATA=3 NOISE=0 GROUPDELAY=1 *| NumOfBlock=1 NumOfParam=0 Output Format for Two-Port Noise Parameters in .sc* Files Output of two-port noise parameter data in .sc* files shows the tabulated data with the following quantities in the following order: *| 2-port noise parameters *| frequency Fmin[dB] GammaOpt(M) GammaOpt(P) RN/Z0 *| {...data...} In this syntax: 466 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 17: Linear Network Parameter Analysis .LIN Analysis ■ Fmin[dB]=minimum noise figure (dB). ■ GammaOpt(M)=magnitude of the reflection coefficient needed to realize Fmin. ■ GammaOpt(P)=phase (degrees) of the reflection coefficient needed to realize Fmin. ■ RN/Z0=normalized noise resistance. Both GammaOpt and RN/Z0 values are normalized with respect to the characteristic impedance of the port=1 element (that is, Z01). Noise Parameters in 2-Port and N-Port Networks You can use the .LIN analysis to compute the equivalent two-port noise parameters or multi-port noise parameters for a network. The noisecalc=1 option automatically calculates the following equivalent circuit values. Vn +In Port=1 Figure 85 Two-Port Network Port=2 Noise Equivalent Circuit ■ Vn is the equivalent input-referred noise voltage source. ■ In is the equivalent input-referred noise current source. ■ InVn is their correlation. The noisecalc=2 option activates N-port noise analysis: .LIN [sparcalc=[1|0] [modelname = modelname]] + [filename = filename] [format=selem|citi|touchstone] + [noisecalc=[2|1|0] [gdcalc=[1|0]] + [mixedmode2port=dd|dc|ds|cd|cc|cs|sd|sc|ss]> + [dataformat=ri|ma|db] Invoking an N-port noise analysis produces an *.nc# file to output the N-port noise correlation matrix in the following format, which is similar to a *.sc# file. HSPICE® User Guide: Simulation and Analysis B-2008.09 467 Chapter 17: Linear Network Parameter Analysis .LIN Analysis *| N=2 DATA=1 NOISE=0 GROUPDELAY=0 COMPLEX_DATAFORMAT=RI *| NumOfBlock=2 NumOfParam=1 ParamNames=res *| ParamSweep res:50 100 *|------------------------------------*| res=50 .MODEL NFQMODEL SP N=2 SPACING=POI INTERPOLATION=LINEAR MATRIX=NONSYMMETRIC + DATA=1 + 100 + 0.457141 0 -0.457141 + -0.457141 0 0.457141 *|------------------------------------*| res=100 .MODEL NFQMODEL1 SP N=2 SPACING=POI INTERPOLATION=LINEAR MATRIX=NONSYMMETRIC + DATA=1 + 100 + 0.514284 0 -0.514284 + -0.514284 0 0.514284 0 0 0 0 The noise analysis data is output in the .lis file in the following format: Frequency = 100.000 Hz NF (mag) = 1.0+1.02857 NF (dB) = 3.07189 Element Contribution to NF (mag) r1 TOT 1.02857 (dB) 122.327m All the 2-port noise parameters are deduced and output in the .lis file with .PRINT/.PROBE commands. HSPICE can output the result of .LIN noise analysis to a .sc*, Touchstone, or CITIfile. Note this limitation for Touchstone files: because Touchstone files currently provide only two-port noise parameters, this type of noise model only supports two-port S-parameter noise analysis for both passive and active systems. Hybrid (H) Parameters .LIN analysis can calculate the complex two-port H (hybrid) parameter of a multi-terminal network. The H parameters of a two-port network relate the voltages and currents at input and output ports: V 1 = h 11 ⋅ I 1 + h 12 ⋅ V 2 468 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 17: Linear Network Parameter Analysis .LIN Analysis I 2 = h 21 ⋅ I 1 + h 22 ⋅ V 2 In the preceding equations: ■ H = h 11 h 12 Hybrid matrix h 21 h 22 ■ V1=Voltage at input port ■ I2=Current at output port ■ V2=Voltage at output port ■ I1=Current at input port You can add the hybrid H parameter matrixes of two networks to describe networks that are in series at their input and in parallel at their output. .LIN can calculate H parameters based on the scattering parameters of the networks. .LIN analysis can extract one-port and two-port network H parameters. For networks with more than two ports, .LIN assumes that the ports numbered 3 and above terminate in their port characteristic impedance (Zc[i], i>2). Group Delay Group delay measures the transit time of a signal through a network versus frequency. It reduces the linear portion of the phase response to a constant value, and transforms the deviations from linear phase into deviations from constant group delay (which causes phase distortion in communications systems). The average delay represents the average signal transit time through a network system. HSPICE can output the result of .LIN group delay measurement to a .sc*, Touchstone, or CITIfile. Group delay is a function of frequency: gd ( w ) = – d ( phase ) -------------------------d(w) Where, HSPICE® User Guide: Simulation and Analysis B-2008.09 469 Chapter 17: Linear Network Parameter Analysis Additional Measurements From .LIN ■ gd=Group delay at the f frequency, 2 πf = w ■ phase=phase response at the f frequency ■ w=radians frequency All complex S, Y, Z, and H parameters support a group delay calculation. Syntax Xmn(T) | Xmn(TD) | X(m,n)(T) | X(m,n)(TD) X=S, Y, Z, or H (parameters) m,n=port number (1 or 2 for H-parameters) The results of the group delay calculation are scalar real numbers in units of seconds. For .LIN, group delay values are a function of frequency. The calculation is: r ij = | r ij | e jf ij ( w ) Differentiating the complex logarithm with respect to omega results in: 1 dr ij 1 d | r ij | df---- ------- = ------- ----------- + j ------r ij dw | r ij | dw dw The group delay is the negative derivative of the phase. Simulation can compute it from the imaginary component of the derivative w.r.t. frequency of the measurement: dr r ij dw 1- ij dfτ ( w ) = – ------ = – Im ---- ------dw Additional Measurements From .LIN In addition to S, Y, Z, and H parameters, a LIN analysis can include the output measurements in the following sections. Impedance Characterizations ■ ■ ZIN(i)=Input impedance at port i (complex, Ohms) ■ 470 VSWR(i)=Voltage standing wave ratio at port i (real, unit-less) YIN(i)=Input admittance at port i (complex, Siemens) HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 17: Linear Network Parameter Analysis Additional Measurements From .LIN Stability Measurements ■ K_STABILITY_FACTOR=Rollett stability factor (real, unit-less) ■ MU_STABILITY_FACTOR=Edwards & Sinsky stability factor (real, unit-less) Gain Measurements ■ G_MAX=Maximum available/operating power gain (real, power ratio) ■ G_MSG=Maximum stable gain (real, power ratio) ■ G_TUMAX=Maximum unilateral transducer power gain (real, power ratio) ■ G_U=Unilateral power gain (real, power ratio) Matching for Optimal Gain ■ G_MAX_GAMMA1=Source reflection coefficient needed to realize G_MAX (complex, unit-less) ■ G_MAX_GAMMA2=Load reflection coefficient needed to realize G_MAX (complex, unit-less) ■ G_MAX_Z1=Source impedance needed to realize G_MAX (complex, Ohms) ■ G_MAX_Z2=Load impedance needed to realize G_MAX (complex, Ohms) ■ G_MAX_Y1=Source admittance needed to realize G_MAX (complex, Siemens) ■ G_MAX_Y2=Load admittance needed to realize G_MAX (complex, Siemens) Noise Measurements ■ VN2=Equivalent input noise voltage squared (real, V2) ■ IN2=Equivalent input noise current squared (real, A2) ■ RHON=Correlation coefficient between input noise voltage and input noise current (complex, unit-less) ■ RN=Noise equivalent resistance (real, Ohms) ■ GN=Noise equivalent conductance (real, Siemens) ■ ZCOR=Noise correlation impedance (complex, Ohms) HSPICE® User Guide: Simulation and Analysis B-2008.09 471 Chapter 17: Linear Network Parameter Analysis Additional Measurements From .LIN ■ YCOR=Noise correlation admittance (complex, Siemens) ■ ZOPT=Optimum source impedance for noise (complex, Ohms) ■ YOPT=Optimum source admittance for noise (complex, Siemens) ■ GAMMA_OPT=Optimum source reflection coefficient (complex, unit-less) ■ NFMIN=Noise figure minimum (source at Zopt) (real, unit-less power ratio) ■ NF=Noise figure (value obtained with source impedance at Z01) (real, unitless power ratio) ■ G_AS=Associated gain -- maximum power gain at NFMIN (real, power ratio) Two-Port Transfer and Noise Measurements Several of the output parameter measurements are assumed to be for two-port networks. When the network has 3 or more ports, the measurements are still carried out by assuming that port=1 is the input and port=2 is the output. All other ports are assumed terminated in their (noiseless) characteristic (z0) impedances. Note that this assumption is equivalent to operating on the twoport [S] submatrix extracted from the multi-port [S] matrix. This is true for both signal and noise calculations. A warning message is issued in cases where N>2 when two-port quantities are requested. Signal and noise port-wise calculations do not require that port elements use a ground reference. Measurements are therefore possible; for example, for fully differential circuits. Since Zopt and Yopt can commonly take on infinite values when computing optimum noise conditions, calculations for optimum noise loading is performed in terms of the reflection coefficient GammaOpt, and is made as robust as possible. Output Format for Two-Port Noise Parameters in .sc* Files The output of two-port noise parameter data in .sc* files are slightly modified. The tabulated data appears with the following quantities in the following order: *| 2-port noise parameters *| frequency Fmin[dB] GammaOpt(M) GammaOpt(P) *| {...data...} RN/Z0 Where 472 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 17: Linear Network Parameter Analysis Additional Measurements From .LIN ■ Fmin[dB] is the minimum noise figure (dB) ■ GammaOpt(M) is the magnitude of reflection coefficient needed to realize Fmin ■ GammaOpt(P) is the phase (degrees) of reflection coefficient needed to realize Fmin ■ RN/Z0 is the normalized noise resistance Both GammaOpt and RN/Z0 values are normalized with respect to the characteristic impedance of the port=1 element; for example, Z01. VSWR The Voltage Standing Wave Ratio represents the ratio of maximum to minimum voltages along a standing wave pattern due to a port’s impedance mismatch. All ports other than the port of interest terminate in their characteristic impedances. VSWR is a real number related to that port’s scattering parameter: 1 + s ii VSWR [ i ] = ----------------1 – s ii ZIN(i) The Input Impedance at the i port is the complex impedance into a port with all other ports terminated in their appropriate characteristic impedance. It is related to that port’s scattering parameter: 1 + S ii ZIN [ i ] = Z 0 i -------------1 – S ii YIN(i) The Input Admittance at the i port is the complex admittance into a port with all other ports terminated in their appropriate characteristic impedance. It is related to that port’s scattering parameter: 1 1 – S ii YIN [ i ] = ------ -------------Z 0 i 1 + S ii HSPICE® User Guide: Simulation and Analysis B-2008.09 473 Chapter 17: Linear Network Parameter Analysis Additional Measurements From .LIN K_STABILITY_FACTOR (Rollett Stability Factor) The Rollett stability factor is: 2 2 2 1 – s 11 – s 22 + Δ K = -------------------------------------------------------2 s 12 s 21 Δ determines the two-port S matrix calculated from this equation: Δ = s 11 s 22 – s 12 s 21 An amplifier where K>1 is unconditionally stable at the selected frequency. MU_STABILITY_FACTOR (Edwards-Sinsky Stability Factor) The following equation defines the Edwards-Sinsky stability factor. 2 1 – | S 11 | μ = ----------------------------------------------------* | S 22 – Δ S 11|+ |S 21S 12| Δ = S 11 S 22 – S 12 S 21 An amplifier with μ>1 is considered unconditionally stable at the specified frequency. Maximum Available Power Gain—G_MAX This is the gain value that can be realized if the two-port is simultaneously conjugate-matched at both input and output (with no additional feedback): s 21 2 G max = --------- ⎛ K – K – 1⎞ ⎠ s 12 ⎝ K is the Rollett stability factor. Special cases of G_MAX are handled in the following manner: ■ If |S12|=0 and (|S11|=1 or |S22|=1), G_MAX=|S21|2 ■ If |S12|=0 and |S11|≠1 and |S22|≠1, G_MAX=G_TUMAX ■ If |S12|≠0 and K≤1, G_MAX=G_MSG When values for K≤1, the Maximum Available Power Gain is undefined, and HSPICE RF returns the Maximum Stable Gain. 474 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 17: Linear Network Parameter Analysis Additional Measurements From .LIN Maximum Stable Gain - G_MSG For a two-port that is conditionally stable (K<1), the following equation calculates the maximum stable gain: s 21 G MSG = --------s 12 To achieve this gain, resistively load the unstable two-port so that K=1, and then simultaneously conjugately match the input and output ports. G_MSG is therefore equivalent to G_MAX with K=1. In terms of admittance parameters: y 21 G MSG = ---------y 12 MSG is equivalent to the Maximum Available Power Gain if K=1. Maximum Unilateral Transducer Power Gain —G_TUMAX This is the highest possible gain that a two-port with no feedback (that is, S12=0) can achieve. 2 s 21 G tumax = -----------------------------------------------------2 2 ( 1 – s 11 ) ( 1 – s 22 ) Unilateral Power Gain—GU This is the highest gain that the active two-port can ever achieve by embedding in a matching network that includes feedback. The frequency where the unilateral gain becomes unity defines the boundary between an active and a passive circuit. The frequency is usually referred to as fmax, the maximum frequency of oscillation. To realize this gain, HSPICE RF neutralizes the feedback of the two-port, and simultaneously conjugate-matches both input and output: HSPICE® User Guide: Simulation and Analysis B-2008.09 475 Chapter 17: Linear Network Parameter Analysis Additional Measurements From .LIN 2 s 21 ------ – 1 s 12 G U = -----------------------------------------------s 21 ⎫ s 21 ⎧ 2 K ------ – 2 Re ⎨ ------ ⎬ s 12 ⎭ s ⎩ 12 Simultaneous Conjugate Match for G_MAX A simultaneous conjugate match is required at the source and load to realize the Gmax gain value. The source reflection coefficient at the input must be: 2 B1 B1 C∗ 1 - ------------ – --------------- – 1 Γ 1 = --------2 C1 2 C1 2 C1 2 2 B 1 = 1 – s 22 + s 11 – Δ 2 C 1 = s 11 – Δ s∗ 22 Δ = s 11 s 22 – s 12 s 21 The load reflection coefficient (G_MAX_GAMMA_2) is: 2 B2 B2 C∗ 2 --------- ------------ – --------------- – 1 Γ2 = 2 C2 2 C2 2 C2 In the preceding equation: 2 2 B 2 = 1 – s 11 + s 22 – Δ ∗ C 2 = s 22 – Δ s11 2 Δ = s 11 s 22 – s 12 s 21 You can obtain useful solutions only when: B1 ------------ > 1 2 C1 B2 ----------- > 1 2 C2 These equations also imply that K>1. 476 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 17: Linear Network Parameter Analysis Additional Measurements From .LIN HSPICE RF derives calculations for the related impedances and admittances from the preceding values. For G_MAX_Z1: 1 + Γ1 Z 1 = Z 01 --------------1 – Γ1 For G_MAX_Z2: 1 + Γ2 Z 2 = Z 02 --------------1 – Γ2 For G_MAX_Y1 1- 1 – Γ 1 Y 1 = ------- --------------Z 01 1 + Γ 1 For G_MAX_Y2 1- 1 – Γ 2 Y 2 = ------- --------------Z 02 1 + Γ 2 Equivalent Input Noise Voltage and Current—IN2, VN2, RHON For each analysis frequency, HSPICE RF computes a noise-equivalent circuit for a linear two-port. The noise analysis assumes that all ports terminate in noise-less resistances. For circuits with more than two ports, ports identified as 3 and above terminate, and the analysis considers only ports 1 and 2. The noise-equivalent circuit calculation results in an equivalent noise voltage and current, and their correlation coefficient. These values are: VN 2 = |v n | 2 IN 2 = |i n | 2 i n v* n RHON = ρ n = -----------------------2 2 | in | | vn | Equivalent Noise Resistance and Conductance—RN, GN These measurements are the equivalent resistance and conductance that would generate the equivalent noise voltage and current values at a temperature of T0 = 290 k in a 1 Hz bandwidth (that is, Δ f = 1 Hz ). HSPICE® User Guide: Simulation and Analysis B-2008.09 477 Chapter 17: Linear Network Parameter Analysis Additional Measurements From .LIN 2 | vn | RN = R n = ----------------4 kT 0 Δ f 2 | in | GN = G n = ----------------4 kT 0 Δ f Noise Correlation Impedance and Admittance—ZCOR, YCOR These measurements represent the equivalent impedance and admittance that you can insert at the input of the noise-equivalent circuit to account for the correlation between the equivalent noise voltage and the current values. 2 ZCOR = ρ n i * vn | vn | n --------- = ------------ = R cor + jX cor 2 2 | in | | in | YCOR = ρ n | in | i nv n * --------- = ------------ = G cor + jB cor 2 2 | vn | | vn | 2 ZOPT, YOPT, GAMMA_OPT – Optimum Matching for Noise The equivalent input noise sources and their correlation make it possible to compute the impedance, admittance, and reflection coefficient values that, if presented at the input of the noisy two-port, result in the best noise performance. These values are: Z opt = Rn 2 ------ – X cor – jX cor Gn 1 Y opt = --------- = Z opt Gn 2 ------ – B cor – jB cor Rn Z opt – Z 01 GAMMA_OPT = Γ opt = ----------------------Z opt + Z 01 Noise Figure and Noise Figure Minimum—NF, NFMIN If you set the input source impedance to ZOPT, the two-port operates with the minimum Noise Figure. The definition of the Noise Figure (F) is unusual because it involves the available gain of the two-port and not its transducer gain. You can express it in the following form: Na F = 1 + --------------------G a kT 0 Δ f 478 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 17: Linear Network Parameter Analysis Additional Measurements From .LIN ■ Ga is the available power gain. ■ Na is the available noise power at the output of the two-port (due solely to the two-port’s noise and not to the input impedance). ■ k is Boltzmann’s constant. ■ T0 is the 290 Kelvin reference temperature. The NMIN minimum noise figure value is computed as: ⎛ Rn 2⎞ N FMIN = F min = 1 + 2 G n ⎜ R cor + ------ – Xcor ⎟ Gn ⎝ ⎠ where NFMIN≥1. For input source impedance values other than ZOPT, the Noise Figure varies as a function of the input source reflection coefficient, according to: 2 R n | Γ S – Γ opt | F = F min + ---------------------------------2 2 Z 01 |1+ Γ opt | The HSPICE RF Noise Figure measurement (NF) returns the noise figure value if the input terminates in the port characteristic impedance (that is, Γ s = 0 ). This value is: Gn R n | Γ opt | 2 NF = F min + --------------------------------- = F min + ------- |Z 01 – Z opt | 2 Z 01 2 Z 01 |1+ Γ opt | Associated Gain—G_As HSPICE RF also includes a measurement named Associated Gain, which assumes that the Γ s in-out impedance is matched for the minimum noise figure (that is, Γ s = Γ opt ), while the output is matched for the maximum gain. 2 2 s 21 ( 1 – Γ Opt ) G AS = -----------------------------------------------------------------2 2 1 – s 11 Γ Opt ( 1 – s ′ 22 ) s 12 s 21 Γ Opt ′ In the preceding equation: s 22 = s 22 + ----------------------------1 – s 11 Γ Opt HSPICE® User Guide: Simulation and Analysis B-2008.09 479 Chapter 17: Linear Network Parameter Analysis Extracting Mixed-Mode Scattering (S) Parameters Extracting Mixed-Mode Scattering (S) Parameters Note: An easily-adapted time domain reflectometry (TDR) example is available in Performing a TDR Simulation in HSPICE in the HSPICE User Guide: Signal Integrity. In HSPICE RF, the .LIN analysis includes a keyword for extracting mixedmode scattering (S) parameters. Syntax .LIN … [ mixedmode2port= dd|dc|ds|cd|cc|cs|sd|sc|ss ] The following keywords in a .PRINT and .PROBE statements specifies the elements in the mixed mode S parameter matrices: S|Y|Z<xy>nm<(t)> Argument Description x, y One of the following: ■ D (differential) C (common) ■ S (single-ended) For example: ■ ■ SCC=common mode S-parameters SDC or SCD=cross mode S-parameters If you omit x,y, then HSPICE uses the value set for the mixedmode2port. ■ Scc Common-mode S-parameters Scd and Sdc Mode-conversion or cross-mode S-parameters m, n port number type One of the following: ■ ■ ■ ■ ■ 480 DB: magnitude in decibels I: imaginary part M: magnitude (default) P: phase in degree R: real part HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 17: Linear Network Parameter Analysis Extracting Mixed-Mode Scattering (S) Parameters Defaults Availability and default value for the mixedmode2port keyword depends on the port configuration. Example 1 p1=p2=single Where, ■ Available: ss ■ Default: ss Example 2 p1=p2=balanced Where, ■ Available: dd,cd,dc,cc ■ Default: dd Example 3 p1=balanced p2=single Where, ■ Available: ds,cs ■ Default: ds Example 4 p1=single p2=balanced Where, ■ Available: sd,sc ■ Default: sd Output File Formats An sc# file format for the mixed mode: HSPICE® User Guide: Simulation and Analysis B-2008.09 481 Chapter 17: Linear Network Parameter Analysis Extracting Mixed-Mode Scattering (S) Parameters ■ The S-element model has additional keywords, such as mixedmodei and idatatype, if the netlist includes one or more balanced ports. ■ The mixedmode2port keyword prints in the header line. ■ The other S-element keywords also appear in the header lines. Touchstone format for the mixed mode: The following lines for data mapping are added to the head of the Touchstone output file if the netlist includes one or more balanced ports. ! ! ! ! S11=SDD11 S12=SDD12 S13=SDC11 S14=SDC12 Two-Port Parameter Measurement Two-port parameter measurement function takes the first 2 ports, then reads the corresponding parameter with the drive condition specified by the mixedmode2port keyword. 482 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 17: Linear Network Parameter Analysis Extracting Mixed-Mode Scattering (S) Parameters Output Format and Description File Type Description *.ac# Output from both the .PROBE and .PRINT statements. *.printac# Output from the .PRINT statement. This is available in HSPICE RF only. *.sc# The extracted S-parameters/2-port noise parameters are written to a *.sc# file by using the S-element format. If you want to simulate the S element, you can reference the *.sc# file in your netlist. * N=numOfPorts DATA=numOfFreq NOISE=[0|1] GROUPDELAY=[0|1] * NumOfBlock=numOfSweepBlocks NumOfParam=numOfSweptParameters * MIXEDMODE=[0|1] DATATYPE=mixedModeDataTypeString .MODEL mname S + N=numOfPorts FQMODEL=SFQMODEL TYPE=S Zo=*** *** ... .MODEL SFQMODEL SP N=numberOfPorts SPACING=POI INTERPOLATION=LINEAR MATRIX=NONSYMMETRIC + DATA= numberOfData + freq1 + s11real s11imag s12real s12imag ... s1Nreal s1Nimag ... + sN1real sN1imag ... sNNreal sNNimag ... ... + freqNumberOfData + s11real s11imag s12real s12imag ...s1Nreal s1Nimag ... + sN1real sN1imag ... sNNreal sNNimag * * * * 2-port noise parameter frequency Fmin [dB] GammaOpt(M) GammaOpt(P) 0.10000E+09 0. 1.0000 0. 1.0281 ... RN/Zo The 2-port noise section starts with “*” so that you can include this file in your HSPICE or HSPICE RF input netlists. Features Supported .LIN analysis in HSPICE and HSPICE RF supports the following features: HSPICE® User Guide: Simulation and Analysis B-2008.09 483 Chapter 17: Linear Network Parameter Analysis Extracting Mixed-Mode Scattering (S) Parameters ■ Automatic calculation of bias-dependent S, Y, and Z parameters. No additional sources required. ■ Automatic calculation of noise parameters. ■ Automatic calculation of group delay matrices. In addition, HSPICE RF supports all existing HSPICE RF models. For noise analysis, HSPICE and HSPICE RF view port 1 as the input and port 2 as the output. Prerequisites and Limitations The following prerequisites and limitations apply to .LIN analysis in HSPICE RF: ■ Requires one .LIN statement to specify calculation options. ■ Requires one .AC statement to specify frequency sweep and parameter sweep. ■ Requires at least one P element, numbered from port 1 to N. ■ For noise analysis, HSPICE RF views port 1 as the input and port 2 as the output. Reported Statistics for the Performance Log (HSPICE RF Only) ■ Simulation time • • ■ DC op time Total simulation time Memory used • 484 Total memory HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 17: Linear Network Parameter Analysis Extracting Mixed-Mode Scattering (S) Parameters Errors and Warnings ■ If the circuit contains fewer than two P-elements and noisecalc=1, then the 2-port noise calculation is skipped. ■ If the circuit contains fewer than two P-elements, does not let you cannot use the .PRINT, .PROBE, or .MEAS command with any two-port noise or gain parameters. ■ If the circuit contains more than two P-elements, all two-port parameters are computed. By default, port=1 is the input and port=2 is the output. All other ports terminate in their reference impedances. Example .OPTION POST=2 .AC DEC 1 20MEG 20G .LIN noisecalc=1 Pout outs gnd port=2 RDC=50 RAC=50 DC=0 AC=1 0 Pin ins gnd port=1 RDC=50 RAC=50 DC=0.5 AC=0.5 0 xlna_2_ ins outs lna .subckt lna in out rhspr5 in _n481 50 rhspr6 _n523 out 100 vvdd _n523 gnd dc=1.8 qhspnpn3 out _n481 gnd gnd bjtm1 area=3 .ends lna .global gnd .END Via Modeling for PCBs in HSPICE You can do modeling of vias for PCBs in pre-layout signal integrity phase of HSPICE simulations. While A 3D field solver is required to accurately model vias, you can use the built-in HSPICE 2D field solver to approximate a via model using the following method: 1. Create a SPICE netlist for a via. The via can be modeled as a lumped pimodel if the via delay is less than 0.1 of the signal edge. HSPICE® User Guide: Simulation and Analysis B-2008.09 485 Chapter 17: Linear Network Parameter Analysis Extracting Mixed-Mode Scattering (S) Parameters L_barrel C-pad Figure 86 C-pad Where: L_barrel is the inductance of the barrel of the via and C_pad is the capacitance of the pad. 2. Use the .LIN command to extract an S-parameter model file in Touchstone format. 3. Use the S-element to use the model file. Other Considerations If you are working with a PCB via, note that it can also be modeled as a Pi Lumped Element Model. The pi-model circuit approximates the behavior of short transmission lines (lumped RLC circuits). But the exact values for the RLC parameters of a via depend on the size and geometry of the via. To determine the exact values, you need to use a 3D field solver, such as the Synopsys Raphael product to extract exact parameter values. Equivalent RLCs for GHz boards require a 3D EM analysis for accurate modeling, such as Raphael provides to include the magnetic flux in the conductor at DC or for modeling edge effects accurately. If Raphael can produce the RLGC table model, you can simulate with the model in HSPICE and then compare the result with field solvers to evaluate the difference. Note that modeling IC vias is more complex as you need to consider stress effects (since process-induced mechanical stress can cause electromigration and formation of voids or cracks in vias or metal lines), thermal effects (since vias have much higher thermal conductivity than the dielectric materials (ILD), and modeling via plug resistance, etc. 486 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 17: Linear Network Parameter Analysis References References [1] Goyal, Ravender. “S-Parameter Output From SPICE Program”, MSN & CT, February 1988, pp. 63 and 66. [2] Robert J. Weber “Introduction to Microwave Circuits”, IEEE Press. [3] Behzad Razavi, “Design of Analog CMOS Integrated Circuits”, McGraw Hill. [4] Reinhold Ludwig, Pavel Bretchko, “RF Circuit Design Theory and Applications”. [5] G.D. Vendelin, Design of Amplifiers and Oscillators by the S-Parameter Method, John Wiley & Sons, 1982. [6] R.S. Carson, High-Frequency Amplifiers, 2nd Edition, John Wiley & Sons, 1982. [7] G. Gonzalez, Microwave Transistor Amplifiers: Analysis and Design, 2nd Edition, Prentice-Hall, 1997. [8] M.L. Edwards and J.H. Sinsky, “A single stability parameter for linear 2-port networks,” IEEE 1992 MTT-S Symposium Digest, pages 885-888. [9] H. Rothe and W. Dahlke, “Theory of noisy fourpoles”, Proc. IRE, volume 44, pages 811-818, June 1956. [10] David E. Bockeman, “Combined Differential and Common-Mode Scattering Parameters: Theory and Simulation,” IEEE trans. on MTT Volume 43, Number 7, Jul. 1995. [11] “Understanding Mixed Mode S-parameters,” http://www.si-list.org/files/tech_files/Understandmm.pdf [12] Robert J. Weber “Introduction to Microwave Circuits”, IEEE Press. [13] Behzad Razavi, “Design of Analog CMOS Integrated Circuits”, McGraw Hill. [14] Reinhold Ludwig, Pavel Bretchko, “RF Circuit Design Theory and Applications.” HSPICE® User Guide: Simulation and Analysis B-2008.09 487 Chapter 17: Linear Network Parameter Analysis References 488 HSPICE® User Guide: Simulation and Analysis B-2008.09 18 Statistical Eye Analysis 18 Describes statistical eye diagram analysis using the .STATEYE command. Analysis of high-speed serial interfaces requires processing of millions of bits of data making analysis by traditional analysis tools computationally expensive. Eye diagrams are used extensively in the evaluation of high-speed serial interfaces and as a fundamental performance metric for high-speed serial interfaces in the bit error rate (BER). Statistical eye diagram techniques allow eye diagrams and BER to be evaluated quickly and accurately. These topics are discussed in the following sections: ■ Statistical Eye Analysis Setup ■ Input Syntax ■ Output Data ■ Examples, Statistical Analysis Setup ■ Known Limitation Important: The .STATEYE command is invoked using the hspicerf executable on the command line for this release (not hspice). However, running a statistical eye analysis only requires an HSPICE license token. Statistical Eye Analysis Setup The port element is used to designate the incident (input) and probe (output) ports for the system to be analyzed. Ports can be specified as single ended or mixed mode. Random jitter can be applied to each incident and probe point in the system. HSPICE® User Guide: Simulation and Analysis B-2008.09 489 Chapter 18: Statistical Eye Analysis Statistical Eye Analysis Setup Each incident port acts as random bit pattern source with specified voltage magnitude. If an incident port element does not have a time domain voltage magnitude specification, the default values, V_high=1.0, V_low=–1.0 are used. Probe ports are used as observation points where .PRINT, .PROBE and .MEASURE statements can be defined. To perform the statistical eye diagram analysis, use the analysis command .STATEYE. Input Syntax The syntax for the .STATEYE command is: .STATEYE T=time_interval Trf=rise_fall_time + Incident_port=idx1, [idx2, … idxN] + Probe_port=idx1, [idx2, … idxN] + [Rj=Rj1, [Rj2, … RjN]] + [tran_init=n_periods] + [V_low=val] [V_high=val] + [T_resolution=n] [V_resolution=n] Parameter T Time of one period of the incident pulse signal (in seconds) Trf Single value (in seconds) to set both the rise and fall times of the incident pulse Incident_port An array of the index numbers of the incident port elements Probe_port An array of the index numbers of the probing port elements Rj An array of the real numbers to specify the standard deviation of the Gaussian random jitter. The array must be in the order of the port element index. No random jitter is added by default. V_low Low voltage level of the incident pulse. The value is used when the voltage level is not specified in the incident port(s). V_high 490 Description High voltage level of the incident pulse. The value is used when the voltage level is not specified in the incident port(s). HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 18: Statistical Eye Analysis Statistical Eye Analysis Setup Parameter Description Tran_init An integer number that specifies the numbers of periods (T) that is used by the initial transient analysis to determine the pulse response of the system. Default value is 30. T_resolution An integer number used to specify the probability density function (PDF) image resolution of the time axis. Default value is 200. V_resolution An integer number used to specify the probability density function (PDF) image resolution of the voltage axis. Default value is 200. Port Element Configuration Incident ports act as pure random bit stream generators in .STATEYE analysis unless either LFSR or PAT source keywords are specified. When either a LFSR or PAT keyword is specified, the incident port will act as a specific bit pattern generator. Port elements that are defined but not specified as an incident or probe port will be assumed to be a DC voltage source with no time dependence. The following statistical eye diagram analysis results can be printed or probed: ■ Eye diagram at a port ■ Bit error rate map at a port ■ Bathtub curve of the bit error rate at a port for specified voltage ■ Bathtub curve of the bit error rate at a port for a specified time .Print and .Probe Syntax .print .print .print .print .print .print .print stateye stateye stateye stateye stateye stateye stateye eye(port_idx) eyeBW(port_idx) eyeV(port_idx,v) eyeT(port_idx,t) ber(port_idx) bathtubV(port_idx,v) bathtubT(port_idx,t) .probe .probe .probe .probe stateye stateye stateye stateye eye(port_idx) eyeBW(port_idx) eyeV(port_idx,v) eyeT(port_idx,t) HSPICE® User Guide: Simulation and Analysis B-2008.09 491 Chapter 18: Statistical Eye Analysis Statistical Eye Analysis Setup .probe stateye ber(port_idx) .probe stateye bathtubV(port_idx,v) .probe stateye bathtubT(port_idx,t) Where: ■ eye(port_idx) specifies the port to output the eye diagram ■ eyeBW(port_idx)specifies the port to output the eye diagram as black and white data ■ eyeV(port_idx,v)specifies the port to output as cross-section of the eye diagram at specified port at specified voltage ■ eyeT(port_idx, t) specifies cross section of the eye diagram at specified port at specified time ■ ber(port_idx) specifies the port to output the bit error rate ■ bathtubv(port_idx, v) specifies the port and voltage to output a bathtub curve ■ bathtubt(port_idx, t) specifies the port and time to output a bathtub curve .Measure Syntax The following statistical eye diagram analysis results can be measured: ■ Vertical eye opening at a specified time ■ Horizontal eye opening at a specified voltage ■ Measure a bit pattern that produces the worst eye opening at a specified time in a high or low state .measure stateye result_name Veye port_idx time=val + [tol=val] .measure stateye result_name Heye port_idx volt=val + [tol=val] .measure stateye result_name WorstBits port_idx time=val + [state=low|high] 492 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 18: Statistical Eye Analysis Statistical Eye Analysis Setup Where, ■ Veye port_idx time=val [tol=val] specifies the port, time and tolerance where the vertical eye opening is to be measured. ■ Heye port_idx volt=val [tol=val] specifies the port, voltage and tolerance where the horizontal eye opening is to be measured. ■ WorstBits port_idx time=val [state=low|high] specifies the port, time and state of the bit pattern that produces the worst eye opening. The default value of tolerance (tol) and logic state (state) are 0 and high, respectively. Output Data Probing Output The .probe stateye command generates netlist.stet# and netlist.stev# for following purposes: ■ netlist.stet#: eye(t,v), eyeBW(t,v), eyeV(t), ber(t,v) and bathtubV(t) ■ netlist.stev#: bathtubT(v) Printing Output The .print stateye command generates the data directory netlist.printSte#/ then stores a convenient gnuplot script for each .print stateye target with necessary data files. For example: ■ The .print stateye eye(2) statement creates the netlist.printSte0/eye_2 script file. ■ The .print stateye bathtubV(2,0.1) creates the netlist.printSte0/bathtub_2_0.1000e+00 script file. On the gnuplot command shell, these scripts can be directly loaded to display the target data. For example, % gnuplot gnuplot> load "printSte0/eye_2" gnuplot> load "netlist.printSte0/bathtub_2_0.1000e+00" HSPICE® User Guide: Simulation and Analysis B-2008.09 493 Chapter 18: Statistical Eye Analysis Statistical Eye Analysis Setup Measurement Output The .measure stateye command generates the netlist.mste# file and stores the measurement results. Examples, Statistical Analysis Setup Incident port definitions p1 tx_in+ tx_in- 0 port=1 p2 in 0 port=2 Probe port definitions p3 rxout+ rxout- 0 port=3 p4 out 0 port=4 Analysis statement .stateye T = 400p trf=20p + incident_Port= 1, 2 + probe_port = 3, 4 + Rj = 5p, 5p, 2p, 2p tran_init = 50 + T_resolution = 300 V_resolution = 300 Print, probe, and measure statements .print .print .print .print stateye stateye stateye stateye eye(4) ber(3) bathtubV(3, 0.9) bathtubT(4, 1n) .probe .probe .probe .probe stateye stateye stateye stateye eye(4) ber(3) bathtubV(3, 0.9) bathtubT(4, 1n) .measure stateye eyevert Veye 4 time=1n tol=0.1n .measure stateye eyehorz Heye 4 volt=0.9 tol=0.05 .measure stateye badbithigh WorstBits 3 time=1n state=high Known Limitation For the current version, a linear time invariant system is assumed for the superposition of the pulse responses even though non-linearities will be taken into account when computing the single bit pulse response. 494 HSPICE® User Guide: Simulation and Analysis B-2008.09 19 Timing Analysis Using Bisection 19 Describes how to use the bisection function in timing optimization. To analyze circuit timing violations, a typical methodology is to generate a set of operational parameters that produce a failure in the required behavior of the circuit. When a circuit timing failure occurs, you can identify a timing constraint, which can lead to a design guideline. You must perform an iterative analysis to define the violation specification. Typical types of timing constraint violations include: ■ Data setup time, before the clock. ■ Data hold time, after the clock. ■ Minimum pulse width required for a signal to propagate to the output. ■ Maximum toggle frequency of the component(s). For more information about optimization, see the HSPICE Simulation and Analysis User Guide Overview of Bisection Before bisection methods were developed, engineers built external drivers to submit multiple parameterized simulations to SPICE-type simulators. Each simulation explored a region of the operating envelope for the circuit. To provide part of the analysis, the driver also post-processed the simulation results, to deduce the limiting conditions. If you characterize small circuits this way analysis times are relatively small, compared with the overall job time. This method is inefficient, due to overhead of submitting the job, reading and checking the netlist, and setting up the matrix. The newer bisection methods increase efficiency when you analyze HSPICE® User Guide: Simulation and Analysis B-2008.09 495 Chapter 19: Timing Analysis Using Bisection Overview of Bisection timing violations, to find the causes of timing failure. Bisection optimization is an efficient cell-characterization method, in Synopsys HSPICE or HSPICE RF. The bisection methodology saves time in three ways: ■ Reduces multiple jobs to a single characterization job. ■ Removes post-processing requirements. ■ Uses accuracy-driven iterations. Figure 87 on page 497 shows a typical analysis of setup-time constraints. Clock and data input waveforms drive a cell. Two input transitions (rise and fall) occur at times T1 and T2. The result is an output transition, when V(out) changes from low to high. The following relationship between the T1(data) and T2 (clock) times must be true for the V(out) transition to occur: T2>(T1+setup time). Characterization or violation analysis determines the setup time. To do this, HSPICE or HSPICE RF keeps T2 fixed and repeats the simulation with different T1 values. It then observes which T1 values produce an output transition and which do not. Before bisection, users had to run tight sweeps of the delay between the data setup and clock edge, and look for the value at which no transition occurs. To do this, you swept a value that specifies how far the data edge precedes a fixed clock edge. This method is time consuming, and is accurate only if the sweep step is very small. Linear search methods cannot accurately determine the setup time value, unless you use extremely small steps from T1 to T2 to simulate the circuit at each point, and monitor the outcome. For example, even if you know that the desired transition occurs during a particular 5ns period, you might need to run 50 simulations to search for the setup time to within 0.1ns over that 5ns period. But the error in the result can be as large as 0.05ns. 496 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 19: Timing Analysis Using Bisection Overview of Bisection T1(varies) T2(fixed) Setup Time = T2 - T1 1 Clock 0 Early enough to cause a good V(out) transition 1 Target value: latest time at which a Data transition results in a V(out) transition Too late for a good transition: V(out) does not change Data 0 1 V(out) 0 Time T1 Setup time is the minimum amount of time by which the Data transition must precede the Clock transition at T2, in order to cause a V(out) transition Figure 87 T2 Bisection can be used to quickly find the latest time T1 at which a Data transition causes a V(out) transition. Determining Setup Time with Bisection Violation Analysis The bisection feature greatly reduces the amount of work and computational time required to find an accurate solution for this type of problem. The following sections show examples of using this feature to identify timing violations for the setup, hold, and minimum clock pulse width. HSPICE® User Guide: Simulation and Analysis B-2008.09 497 Chapter 19: Timing Analysis Using Bisection Bisection Methodology Bisection Methodology Bisection is an optimization method that uses a binary search method, to find the value of an input variable (target value). This variable is associated with a goal value of an output variable. The type of the input and output variables can be voltage, current, delay time, or gain, related by some transfer function. In general, use a binary search to locate the goal value of the output variable within a search range of the input variable. Then, iteratively halve that range to rapidly converge on the target value. At each iteration, HSPICE or HSPICE RF compares the measured value of the output variable with the goal value. Both the pass/fail method and the bisection method use bisection (see Using Bisection on page 498). The bisection procedure consists of two measurement and optimization steps, when solving the timing violation problem: ■ Detecting whether the output transition occurred. ■ Automatically varying the input parameter (T1 in Figure 87 on page 497) to find the value for which the transition barely occurs. Measurement Use the MAX measurement function to detect the success or failure of an output transition. For a low-to-high output transition, a MAX measurement produces zero on failure, or approximately the Vdd supply voltage on success. This measurement, using a goal of Vdd (minus a suitable small value to ensure a solution), is sufficient to drive the optimization. Optimization The bisection method is straightforward if you specify a single measurement with a goal, and known upper and lower boundary values for the input parameter. The characterization engineer must specify acceptable upper and lower boundary values. Using Bisection Before you can use bisection, you must specify the following: 498 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 19: Timing Analysis Using Bisection Using Bisection ■ A pair of values, for the upper and lower boundaries of the input variables. To find a solution, one of these values must result in an output variable >|goal value| and the other must result in <|goal value|. ■ A goal value. If there is no goal keyword in the statement, the goal value will not be defaulted to zero, and HSPICE considers the measure result as a relative error expression. ■ Error tolerance value. The bisection process stops when the difference between successive test values is ≤ error tolerance. If the other criteria are also met, see the following steps. ■ Related variables. Use a monotonic transfer function to relate variables where a steadily-progressing time (increase or decrease) results in a single occurrence of the goal value at the target input variable value. HSPICE or HSPICE RF includes the error tolerance in a relation, used as a process-termination criterion. Figure 88 on page 504 shows an example of the binary search process that the bisection algorithm uses. This example is the pass/fail type, and is appropriate for a setup-time analysis that tests for the presence of an output transition. In the example depicted in Figure 87 on page 497 note that: 1. A long setup time TS (= T2 - T1) results in a VOUT transition (a pass). 2. A too-short setup time (where the latch has not stabilized the input data, before the clock transition) results in a fail. Explanation: For example, you might define a pass time value as any setup time, TS, that produces a VOUT output minimum high logic output level of 2.7V, which is the goal value. 3. The target value is a setup time that just produces the VOUT value of 2.7V. Finding the exact value is impractical, if not impossible, so you need to specify an error tolerance to calculate a solution arbitrarily close to the target value. 4. The bisection algorithm performs tests for each specified boundary value to determine the direction in which to pursue the target value, after the first bisection. In this example shown in Figure 87 on page 497, the upper boundary has a pass value and the lower boundary has a fail value. 5. To start the binary search you specify the lower and upper boundaries. The program tests the point midway between the lower and upper boundaries (see Figure 88 on page 504). HSPICE® User Guide: Simulation and Analysis B-2008.09 499 Chapter 19: Timing Analysis Using Bisection Using Bisection • If the initial value passes the test, the target value must be less than the tested value (in this example). The bisection algorithm moves the upper search limit to the value that it just tested. • If the test fails, the target value must be greater than the tested value. Bisection moves the lower limit to the value that it just tested. 6. The algorithm tests a value midway between the new limits. 7. The search continues in this manner, moving one limit or the other to the last midpoint, and testing the value midway between the new limits. 8. The process stops when the difference between the latest test values is less than or equal to the error tolerance that you specified. To normalize this value, multiply by the initial boundary range. For more information about using the .MODEL statement for bisection, see the HSPICE and HSPICE RF Command Reference. Examining the Command Syntax The following syntax is used for bisection: .MODEL <OptModelName> OPT METHOD=BISECTION ... -or.MODEL <OptModelName> OPT METHOD=PASSFAIL ... OptModelName is the model to be used. Refer to the HSPICE Simulation and Analysis User Guide for name information on specifying optimization models in HSPICE. The METHOD keyword specifies which optimization method to use. The OPT keyword indicates that optimization is to be performed. For bisection, the method can be one of the following: ■ BISECTION When the difference between the two latest test input values is within the error tolerance and the latest measured value exceeds the goal, bisection has succeeded and then ends. This process reports the optimized parameter that corresponded to the test value that satisfies this error tolerance and this goal (passes). ■ PASSFAIL When the difference between the last two optimization parameter test values is < the error tolerance and the associated goal measurement fails for one of the values and passes for the other, bisection has succeeded and 500 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 19: Timing Analysis Using Bisection Using Bisection then ends. The process reports the optimization parameter test value associated with the last passing measurement. “Pass” is defined as a condition in which the associated goal measurement can produce a valid result. “Fail” is defined as a condition in which the associated goal measurement is unable to produce a valid result. For example, if the measurement is of TRIG/TARG form, and the TARG event is not found, then this optimization parameter test value is deemed a failure. When using PUSHOUT bisection, the definition of a failure is modified to also include any goal measurement result that is valid and > the push-out specification. The parameters are passed in a normal optimization specification: .PARAM <ParamName>=<OptParFun> (<Initial>, <Lower>, <Upper>) In the BISECTION method, the measure results for <Lower> and <Upper> limits of <ParamName> must be on opposite sides of the goal value in the .MEASURE statement. In the PASSFAIL method, the measure must pass for one limit and fail for the other limit. The process ignores the value of the <Initial> field. The error tolerance is a parameter in the model which is being optimized. Using the BISECTION method, a bisectional search is applied to multiple parameters. The logical relationship of these parameters is based on 'AND'. In the PASSFAIL method, a bisectional search is applied to only one parameter. When the OPTLST option is set (.OPTION OPTLST=1), the process outputs the following information for the BISECTION method: bisec-opt iter = <num_iterations> xlo = <low_val> xhi = <high_val> x = <result_low_val> xnew = <result_high_val> err = <error_tolerance> The x is the old parameter value and xnew is the new parameter value. When .OPTION OPTLST=1, the process outputs the following information for the PASSFAIL method: bisec-opt iter = <num_iterations> xlo = <low_val> xhi = <high_val> x = <result_low_val> xnew = <result_high_val> measfail = 1 In this syntax, measfail=0 for a test failure for the x value. Performing Transient Analyses with Bisections When performing transient analysis bisection with the .TRAN statement, use the following syntax: HSPICE® User Guide: Simulation and Analysis B-2008.09 501 Chapter 19: Timing Analysis Using Bisection Setup Time Analysis .TRAN <TranStep> <TranTime> SWEEP OPTIMIZE=<OptParFun> + RESULTS=<MeasureNames> MODEL=<OptModelName> When performing a transient analysis bisection with the .MEASURE statement, use the following syntax: .MEASURE TRAN <MeasureName> <MeasureClause> GOAL=<GoalValue> Setup Time Analysis This example uses a bisectional search to find the minimum setup time for a D flip-flop. The circuit for this example is dff_top.sp, which is located in directory <\$installdir>/demo/hspice/bisec. Figure 88 on page 504 and Figure 89 on page 505 show the results of this demo. HSPICE or HSPICE RF does not directly optimize the setup time, but extracts it from its relationship with the DelayTime parameter (the time before the data signal), which is the parameter to optimize. Input Listing The following portion of the input listing shows how .TRAN analysis, the DelayTime parameter, and .MEASURE statements are used in bisection: 502 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 19: Timing Analysis Using Bisection Setup Time Analysis * DFF_top Bisection Search for Setup Time * PWL Stimulus v28 data gnd PWL + 0s 5v + 1n 5v + 2n 0v + Td = "DelayTime" \$ Offsets Data from time by DelayTime v27 clock gnd PWL + 0s 0v + 3n 0v + 4n 5v * Specify DelayTime as the search parameter and provide * the lower and upper limits. .PARAM DelayTime= Opt1 ( 0.0n, 0.0n, 5.0n ) * Transient simulation with Bisection Optimization .TRAN 0.1n 8n SweepOptimize = Opt1 + Result = MaxVout\$ Look at measure + Model = OptMod * This measure finds the transition if it exists .MEASURE Tran MaxVout Max v(D_Output) Goal = ‘v(Vdd)’ * This measure calculates the setup time value .MEASURE Tran SetupTimeTrig v(Data)Val = ‘v(Vdd)/2’ + Fall = 1 + Targ v(Clock)Val = ‘v(Vdd)/2’ + Rise = 1 * Optimization Model .MODEL OptMod Opt + Method = Bisection .OPTION Post Brief NoMod HSPICE® User Guide: Simulation and Analysis B-2008.09 503 Chapter 19: Timing Analysis Using Bisection Setup Time Analysis Measured value Y - volts in this case First bisection value is mid-way between specified boundaries. First test value passes because measured value > goal value (2.7 V in this case). X1 = (XU + XL)/2 ~5V Output signal present for all TS target value Goal = 2.7V Target value Lower boundary XL - test fails Input variable X - Setup time Ts in this case Upper boundary XU - test passes First test value - passes First test value becomes new upper test limit. Second test value is mid-way between new upper limit and lower boundary. Second test value fails. v X2 = (X1 + XL)/2 XL X1 Target XU X XU X Second test value - fails X2 = (X1 + X2)/2 v Second test value becomes new lower limit. Third test value is mid-way between new lower limit and current upper limit. XL X2 X1 Third test value - passes Continue halving the test region until the interval between successive test values meets the criterion: then report the value X, (associated with the measured value the passed). If you select the bisection method, the reported value must correspond with the condition: measured value - goal > 0 Figure 88 504 Bisection Example for Three Iterations HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 19: Timing Analysis Using Bisection Setup Time Analysis Results The top plot in Figure 89 shows the relationship between the clock and the data pulses that determine the setup time. The bottom plot is the output transition. Figure 89 Transition at Minimum Setup Time Find the actual value for the setup time in the “Optimization, Results” section of the input listing file: optimization completed, the condition relin = 1.0000E-03 is satisfied **** optimized parameters opt1 .PARAM DelayTime = 1.7822n ... maxvout = 5.0001E+00 at= 4.8984E-09 from = .0000E+00 to= 8.0000E-09 setuptime= 2.1777E-10 targ= 3.5000E-09 trig= 3.2822E-09 This listing file excerpt shows that the optimal value for the setup time is 0.21777ns. The top plot in Figure 90 on page 506 shows examples of early and late data transitions, and the transition at the minimum setup time. The bottom plot HSPICE® User Guide: Simulation and Analysis B-2008.09 505 Chapter 19: Timing Analysis Using Bisection Minimum Pulse Width Analysis shows how the timing of the data transition affects the output transition. The following analysis statement produces these results: * Sweep 3 values for DelayTime Early Optim Late .TRAN 0.1n 8n Sweep DelayTime Poi 3 0.0n 1.7822 Figure 90 5.0n Early, Minimum, and Late Setup and Hold Times This analysis produces the following results: *** parameter DelayTime = .000E+00 *** \$ Early setuptime= 2.0000E-09 targ= 3.5000E-09 trig= 1.5000E-09 *** parameter DelayTime = 1.7822E-09 *** \$ Optimal setuptime= 2.1780E-10 targ= 3.5000E-09 trig= 3.2822E-09 *** parameter DelayTime = 5.000E-09 *** \$ Late setuptime= -3.0000E-09 targ= 3.5000E-09 trig= 6.5000E-09 Minimum Pulse Width Analysis This example uses a pass/fail bisectional search to find a minimum pulse width required so the input pulse can propagate to the output of an inverter. It is based on demonstration netlist iva_a.sp, which is available in directory \$<installdir>/demo/hspice/bisect. Figure 91 on page 507 shows the results of this demo. 506 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 19: Timing Analysis Using Bisection Pushout Bisection Methodology Input Listing Directory This input listing file is located in: \$installdir/demo/hspice/bisect/inv_a.sp. Results Figure 91 shows results of pass/fail search, for two different capacitive loads. Figure 91 Results of Bisectional Pass/Fail Search Pushout Bisection Methodology For setup- or hold-time optimization analysis, a normal bisection method varies the input timing to find the point just before failure. At this point, delaying the input longer results in failure, and the output does not transition. In pushout analysis, instead of finding the last point just before failure, the first successful output transition is used as the golden target. You can then apply a maximum allowed pushout time to decide if the subsequent results are classified as passes or failures. Finding the optimized pushout result is similar to a normal bisection because both use a binary search to approach the desired solution. The main difference is the goal or the optimization criteria. HSPICE® User Guide: Simulation and Analysis B-2008.09 507 Chapter 19: Timing Analysis Using Bisection Pushout Bisection Methodology The following example (Figure 92 on page 508) shows a transition of Vin with a varying delay during a Vclck transition. When the “lower” input transitions, it indicates that the device being tested is functioning. The “upper” input does not transition, which indicates that the device is not functioning. Lower Pushout Norm Upper Vin Ts Tp Vclk Lower Pushout Norm Upper Vout Delta Figure 92 Pushout Bisection Example Consider the pushout bisection example located in the following directory: \$installdir/demo/hspice/bisect/dff_push.sp The transition of Vin is delayed by varying amounts with respect to a Vclk transition. For the Lower input transition, the output transitions and indicates that the device under test is functioning. For the Upper input transition, the output does not transition and indicates that the device is not functioning. Normal bisection varies the input timing to find the point just before failure (called Norm here). At this point, a failure occurs when the device is delayed longer and the output does not transition. The circuit works at points between Lower and Norm, but the output transition is delayed from the lower conditions 508 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 19: Timing Analysis Using Bisection Pushout Bisection Methodology by setting Delta. This is called the Pushout. The pushout can also lie between Norm and Upper, which depends on your use of the lower or upper option. In you use normal bisection in this example, the resulting gain is delaytime=7.374e-10 pushout=-1.672e-09. Instead, when setting pushout=0.01, the result is delaytime=3.918e-11 pushout=3.970e-09. HSPICE® User Guide: Simulation and Analysis B-2008.09 509 Chapter 19: Timing Analysis Using Bisection Pushout Bisection Methodology 510 HSPICE® User Guide: Simulation and Analysis B-2008.09 20 20 Analyzing Variability and Using the Variation Block Introduces variability, describes how it can be defined in HSPICE, and introduces the Variation Block. The topics are covered in the following sections: ■ Overview of Variation on Silicon ■ Defining Variability in HSPICE ■ Overview of the Variation Block ■ Variation Block Structure ■ Variation Block Examples ■ Group Operator {...} and Subexpressions ■ Interconnect Variation in Star-RCXT with the HSPICE Flow ■ Control Options and Syntax Overview of Variation on Silicon As semiconductor technologies migrate to ever-smaller geometries, larger relative variations in device characteristics are being observed. These fluctuations in device characteristics have been analyzed and classified for the purpose of dealing with the variations in manufacturing during the design phase. The following types of variations can be identified at the wafer level: ■ Global variations from foundry, lot, or wafer processing ■ Across wafer variations due to materials and gas flow, generally linear across the area of a chip ■ Across wafer variations due to thermal, optical, and spin processes, generally linear across the area of a chip HSPICE® User Guide: Simulation and Analysis B-2008.09 511 Chapter 20: Analyzing Variability and Using the Variation Block Overview of Variation on Silicon As a result of microscopic random processes, local variations are observed between closely spaced identically designed devices. Microscopic variations include line edge roughness, finite number of dopant atoms in the channel, and atomic level oxide thickness changes. In analog design, certain circuit characteristics can be made insensitive to global variations by applying the concept of matched devices; however these characteristics are then affected by the local variations. In digital designs for nanometer technologies, large local variations can cause unacceptable variations in path delays and signal slopes. Large circuits suffer from spatial or position dependent variations, which create problems with clock skew for devices that are far apart. Finally device characteristics are affected by features in proximity (metal coverage, fill patterns, mechanical strain, shape variation due to lithography, etc.) and orientation. Some of these variations are systematic and can be accounted for in design or post-layout verification. Historically, only the effects of variation on device characteristics (transistors, resistors, and capacitors) have been considered. In nanometer technologies, the variations on the interconnect also need to be taken into account because the relative variation in the resistance and capacitance has increased due to smaller wire width and inter conductor spacing. These variations combined, summarized as parametric variability, dominate yield loss in the nanometer technologies. The circuits function in terms of connectivity, but do not meet specifications on metrics such as speed, leakage, or offset. For example while the threshold of MOS devices gets smaller, approaching 200mV, the variation in threshold gets larger, with standard deviation up to 30mV for short devices. Due to the low supply voltages, in combination with requirements for high speed, the circuits stop working with these large spreads in device characteristics. Therefore, simulating (or predicting) the effects of these variations on circuit response is increasingly important, in particular when considering the high mask costs and time to market constraints for the majority of today's products. To be able to simulate the effects of the variations in device characteristics due to materials and manufacturing, they need to be described in a way that the simulator can handle. Traditionally, the global variations were specified through process corner files, and the other types of variations mentioned above were either guessed or ignored. In recent years, statistics blocks were added to the model files. They describe variations in terms of distributions on device model parameters. An even newer approach for defining variations is the Variation Block, described later in this chapter. 512 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 20: Analyzing Variability and Using the Variation Block Defining Variability in HSPICE The following analyses are available in HSPICE to simulate the effects of variations on circuit response: ■ Monte Carlo analysis is the traditional method for finding the variation in circuit response resulting from the parameter variations. ■ DC and AC mismatch analyses are efficient methods for simulating the effects of local variations on a circuit's DC or AC response. To get satisfactory answers from these analyses, the variation definitions must have been generated for the target technology of the design, similar to device models. Defining Variability in HSPICE Three approaches are available for defining variability in HSPICE: ■ Defining a Variation Block; for example, .Variation global and local variation definitions .End_Variation ■ Defining variations on parameters; for example, .param var=agauss(20,1.2,3) For a discussion of this topic, see Appendix A, Statistical Analysis. ■ Defining variations on models using lot and dev parameters in the model file; for example, vth0=0.6 lot/0.1 dev/0.02 For a discussion of this topic, see Appendix A, Statistical Analysis. The Variation Block approach replaces the older methods of defining variations on parameters and models in HSPICE because it best fulfills the requirements for simulating nanometer technology devices. The advantages of the Variation Block over previous solutions are: ■ The Variation Block consolidates variation definitions in single records. ■ A clear distinction exists between Global, Local, and Spatial Variations. ■ A subset of variation types can be selected in a dependent simulation. HSPICE® User Guide: Simulation and Analysis B-2008.09 513 Chapter 20: Analyzing Variability and Using the Variation Block Overview of the Variation Block ■ The syntax allows for defining Local and Global Variation as a function of device geometry, and Spatial Variation as a function of device location. ■ Monte Carlo results derived from the Variation Block are consistent with those from DCMatch or ACMatch analyses. The following sections present these topics: ■ Overview of the Variation Block ■ Variation Block Structure ■ Variation Block Examples ■ Interconnect Variation in Star-RCXT with the HSPICE Flow ■ Control Options and Syntax Overview of the Variation Block The characteristics of circuits produced in semiconductor processing are subject to variability, as is the case for any manufactured product. For a given target technology, the nominal device characteristics are described with a set of parameters, which applies to a certain device model (for example, BSIM4). In HSPICE, the variability of the model parameters is described through a Variation Block. A Variation Block is a container for specifying variations introduced by the effects in manufacturing on geometry and model parameters. For the purpose of dealing with variations in HSPICE, they are modeled as Global, Local, or Spatial variations. ■ ■ Local Variations are defined as variations between devices in proximity, or with common centroid layout on the same chip; they are caused by the microscopic variations in materials and geometry, and affect different devices differently. ■ 514 Global Variations are defined as variations in device characteristics from lot to lot, wafer to wafer and chip to chip; they are caused by variations in starting material and differences between equipment and procedures. Global Variations affect all devices with the same model name in the same way. Spatial Variations are defined as variations due to the physical arrangement of the devices on the layout; they are caused by gradients from material properties, imperfections of lenses, and spin processes. The dependence on distance means that large or distributed circuits are more affected by Spatial Variations. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 20: Analyzing Variability and Using the Variation Block Variation Block Structure All three classes can be described in the Variation Block in a very flexible way by user-defined expressions. Since there are currently no industry-wide standards for specifying process variability, this feature allows each company to implement their own proprietary model for variability. The Variation Block is generally provided by a modeling group, very similar to device models (for example, BSIM) because it must be created specifically for each technology from test circuits. Like a model, the Variation Block can be part of a library which is encrypted; therefore, the content is not accessible to the designers. They can add a separate Variation Block in their netlist, to define options and variations on generic elements. See Control Options and Syntax and Variations of Element Parameters. The structure of the Variation Block allows for building expressions to model interdependence and hierarchy of the variations. For example, one random variable can control the variation in oxide thickness of both PMOS and NMOS devices, as it is generally the same for both types of devices. Note that the earlier methods for specifying variation are not compatible with the Variation Block. For controlling the behavior of Variation Blocks, see section on options for controlling the behavior. The Variation Block is currently used for Monte Carlo, DC and AC mismatch analyses; for a description of these analyses, see Chapter 21, Monte Carlo Analysis Using the Variation Block Flow and Chapter 22, Mismatch Analyses, respectively. For the functions available to build expressions as presented in the next sections, see Parameters and Functions on page 273. Variation Block Structure A Variation Block is structured in four sections: ■ general section ■ subblock for Global Variations ■ subblock for Local Variations ■ subblock for Spatial Variations This discussion presents the syntax of a Variation Block, followed by discussion of the contents of the four sections. HSPICE® User Guide: Simulation and Analysis B-2008.09 515 Chapter 20: Analyzing Variability and Using the Variation Block Variation Block Structure .Variation Define options Define common parameters that apply to all subblocks .Global_Variation Define the univariate independent random variables Define additional random variables through tranformations Define variations of model parameters .End_Global_Variation .Local_Variation Define the univariate independent random variables Define additional random variables through transformations Define variations of model parameters .Element_Variation Define variations of element parameters .End_Element_Variation .End_Local_Variation .Spatial_Variation Define the univariate independent random variables Define additional random variables through tranformations Define variation of model parameters .End_Spatial_Variation .End_Variation General Section In the general section, options can be defined that control the variability analyses which use the content of the Variation Block. Options can be specified, one per logical record. Note: “.Option” (with a leading period) does not work for options specified in the Variation Block. The correct syntax is: Option OptionName = value See Control Options and Syntax at the end of this chapter for a listing and description of Variation Block control options. Parameters, also, can be defined that apply to all subblocks in which variations are specified; however, these cannot contain any distribution related functions. Parameters defined within a Variation Block are completely independent of parameters defined outside of it. Example: parameter PI=3.1416 516 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 20: Analyzing Variability and Using the Variation Block Variation Block Structure Subblocks for Global, Local and Spatial Variations Within the variation subblocks, univariate independent random variables can be defined. These are random variables with specific distributions over a certain sample space. Additional random variables can be generated through transformations. These random variables form the basis for correlations and complicated distributions. A basic rule of the Variation Block approach is to have the model definition on the top level, instead of inside of a subcircuit, as necessary in the old approach.In all three subblocks, variations on model parameters can be defined. This is where global or Local Variations on the parameters of semiconductor devices are specified. A special section within the subblock for Local Variations allows for defining Local Variations on elements. This is either for specifying local temperature variations or variations on generic elements that do not have a model, as used early in the pre-layout design phase, or for off-chip components; for example, resistors and capacitors. Local and Global variation support the block operator brackets described in Group Operator {...} and Subexpressions on page 531. Independent Random Variables When describing variations, a standard normal (Gaussian) distribution is assumed, unless otherwise specified explicitly. This default behavior is explained in later sections. Other types of distributions or correlations are modeled by applying transformations to the independent random variables. These independent random variables come from three basic distributions: ■ Uniform distribution: defined over the range from -0.5 to 0.5: U() ■ Normal distribution: with mean=0 and variance=1, default range +/-4: N() ■ User-defined cumulative distribution function: CDF(xyPairs) If f(x) is the probability density of a random variable x, then the cumulative distribution function is the integral of f(x). A cumulative distribution function can be approximated by a piecewise linear function, which can be described as a sequence of pairs of points [xi, yi]. The following rules apply: 1. at least two pairs are required 2. white space or a comma is required between each number 3. the CDF starts at zero: y1=0 4. CDF ends at one: yn=1 HSPICE® User Guide: Simulation and Analysis B-2008.09 517 Chapter 20: Analyzing Variability and Using the Variation Block Variation Block Structure 5. xi values must be monotonically increasing xi+1 > xi 6. yi values must be monotonically non-decreasing yi+1 ≥ yi ∞ 7. ∫ x ⋅ f ( x ) ⋅ dx = 0 –∞ Example Parameter var=CDF(-0.1 0 -0.05 0.5 0.05 0.5 0.1 1.0) This CDF produces for 1000 samples: The distributions N() and U() do not accept any arguments. The syntax for defining independent random variables is: Parameter a=U() b=N() c=CDF(x1,y1,......xn,yn) These distributions cannot be defined within expressions; variables must be assigned and then the variables can be used within expressions. Dependent Random Variables To model distributions which are more complicated than the ones which are available through the predefined independent random variables, transformations can be applied by using expressions on independent random variables. A dependent variable can also be created as a function of more than one independent random variable to express correlation. 518 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 20: Analyzing Variability and Using the Variation Block Variation Block Structure Example 1 This example creates a random variable with normal distribution, with mean A and standard deviation B. Parameter var=N() Y='A + B * var' Example 2 This example creates a random variable with a uniform distribution from D to E, where D and E are arbitrary constants. Parameter var=U() Y='0.5*(D+E) + (E-D) * var' Example 3 This example creates a random variable with two peaks. Parameter a=N() b=N() c='a+2*sgn(b)' Absolute Versus Relative Variation By default, the specified variation is absolute, which means additive to the original model or element parameter; however, sometimes it is more appropriate to specify relative variations that are defined by appending a space and a “%” sign to the expression. The simulator divides the result of the expression by 100, and multiplies by the original parameter value and the random number from the appropriate generator to calculate the change. Example In the following example, the variation on the threshold parameter vth0 is specified as absolute (sigma of 80 or 70mV), the variation on the mobility u0 as relative (15 or 13 percent). .Global_Variation Nmos snps20N vth0=0.08 u0=15 % Pmos snps20P vth0=0.07 u0=13 % .End_Global_Variation HSPICE® User Guide: Simulation and Analysis B-2008.09 519 Chapter 20: Analyzing Variability and Using the Variation Block Variation Block Structure Variations on Model Parameters Variations on model parameters can be defined in subblocks for Global, Local, and Spatial Variation. In the course of the simulation, these variations are then applied to the specified device model parameters. Model parameter variations are described with the following syntax: Model_Type Model_Name Model_Parameter=Expression for Sigma The syntax Model_Parameter=Expression for Sigma is a shorthand notation for Variation_in_Model_Parameter=’Expression for Sigma’. If the expression references only constants and parameters that evaluate to constants, then a Gaussian variation with zero mean and a sigma equal to the expression is automatically implied. To describe variation as a function of previously defined independent random variables, use the construct 'Perturb()', with the following syntax: Model_Type Model_Name Model_Parameter=Perturb(’Expression’) The expression for sigma may need to be enclosed in quotes, see the general HSPICE rules for Using Algebraic Expressions on page 278. The following lines define a global Variation, with implicit normal distribution, with zero mean and sigma of 10, on the parameter rsh of resistors with model Rpoly. .Global_Variation R Rpoly rsh=10 .End_Global_Variation In the next example, the independent variable Toxvar is used to model global Variations on oxide thickness. Toxvar is an independent random variable with a normal distribution, with mean=0 and sigma=1. In the device models nch and pch, Toxvar is applied to the parameters tox with a different multiplier. The oxide thicknesses in the two models vary in parallel; they are correlated. .Global_Variation Parameter Toxvar=N() Nmos nch tox=Perturb('7e-10*Toxvar') Pmos pch tox=Perturb('8e-10*Toxvar') .End_Global_Variation HSPICE supports the following model types: NMOS, PMOS, R, Q, D, and C. 520 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 20: Analyzing Variability and Using the Variation Block Variation Block Structure Variations can only be defined on parameters that are explicitly specified in the associated device model. For a list of supported models and parameters see “Supported Models and Parameters for HSPICE variability” on SolvNet. For binned models, variations can be defined separately by specifying the model name with the bin extension; for example, devices from bins 1 and 2 receive different variation on the parameter lint, which models length variation: Nmos snps20N.1 lint=10n Nmos snps20N.2 lint=12n Variations on Subcircuit Parameters The Variation Block allows for defining variation on parameters, which are specified in the subcircuit definition record, with a default value. The default parameter values can be overwritten by specifying them at subcircuit instantiation. The syntax is: Subckt SubcktName Parameter='expression for sigma' The following rules apply for these types of definitions: ■ Only parameters that are defined as formal numeric arguments on the subcircuit definition record can be subject to variation. (This is the line which starts with .SUBCKT and possibly has continuation lines.) ■ The subcircuit must not be defined within another subcircuit. ■ If the subcircuit contains a model, then variations on the model parameters, as described in section, Variations on Model Parameters, are not supported. Instead, variations need to be defined on a subcircuit parameter and the parameter used inside of the model. Subcircuit Parameters Variation Use Models The subckt parameters variation feature addresses the following three needs: ■ A component is defined with an expression, which is not available in a model: r1 1 0 'Rsh*l/w*(1+b1*(tanh(b2*abs(v(1,0)/l))))' HSPICE® User Guide: Simulation and Analysis B-2008.09 521 Chapter 20: Analyzing Variability and Using the Variation Block Variation Block Structure This expression models a voltage dependent resistor, with non-linear dependence not available in a traditional model. If this resistor is called within a subcircuit, and parameters are specified on the subcircuit definition record, then variation can be modeled, for example, on Rsh, l and w: Example 1 i1 0 1 1m x1 1 0 rtanh .subckt rtanh a b rsh=1k w=1u l=1u .param b1 = -0.4 b2 = 8u r1 a b 'Rsh*l/w*(1+b1*(tanh(b2*abs(v(a,b)/l))))' .ends .Variation .Global_Variation subckt rtanh rsh=10 % .End_Global_Variation .Local_Variation subckt rtanh rsh=3 % .End_Local_Variation .End_Variation ■ A component is represented by a network, and the subcomponents must have the same value when local variations are specified: Example 2 r1 end1 middle rmodel w='w+dw' l='l/2+dl' r2 end2 middle rmodel w='w+dw' l='l/2+dl' c1 middle sub cmodel w=w l=l In this example, the resistor has a center tap, where a capacitor is connected. If these three components are defined within a subcircuit and parameters dw, dl, and rsh are defined on the subcircuit definition record, 522 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 20: Analyzing Variability and Using the Variation Block Variation Block Structure then the two resistors of the same network always have the same value; local variations only cause different instantiations of the subcircuit to have different equivalent resistance between the network terminals. ■ Users need to calculate the value of a device model parameter through an equation because the built-in equations are not adequate: Example 3 .subckt nch n1 n2 n3 n4 dvth0_glob=0 dvth0_loc=0 du0_glob=0 du0_loc=0 + dtox=0 dlint=0 dwint=0 l=60n w=120n as='w*90n' ad='w*90n' ... .param vth0_base=0.345 u0_base=0.015 .param vth0_geo=function1(w,l,temper,vth0_base) .param u0_geo=function2(w,l,temper,u0_base) .param dvth0_geo=function3(w,l,dvth0_loc) .param du0_geo=function4(w,l,temper,du0_loc) M1 n1 n2 n3 n4 nch25 w=w l=l as=as ad=ad ... .MODEL nch25 NMOS LEVEL = 54 + vth0='vth0_geo+dvth0_glob+dvth0_geo' u0='u0_geo*(1+du0_glob)*(1+du0_geo)' + tox='2.6n+dtox' lint='2.1n+dlint' wint='5.3n+dwint' ... .ends X1 d1 g1 s1 b1 nch l=60n w=150n X2 d2 g2 s2 b2 nch l=80n w=120n .Variation .Global_Variation subckt nch dvth0_glob=0.03 dtox=0.12n du0_glob=0.2 dlint=2n dwint=3n .End_Global_Variation .Local_Variation subckt nch dvth0_loc=2.0m dtox=0.03n du0_loc=0.03 dlint=21p dwint=47p .End_Local_Variation .End_Variation The values of model parameters vth0 and u0 are defined through user defined equations (function1 and function2), with dependency on device size and temperature. This necessitates a local model (nch25). The parameters with variations are declared on the subcircuit definition line. In this example, global and local variations are processed differently through the subcircuit, therefore the respective variations have to be specified on separate parameters. Global variations (dvth0_glob and du0_glob) are applied to the model parameters vth0 and u0 directly. Local variation HSPICE® User Guide: Simulation and Analysis B-2008.09 523 Chapter 20: Analyzing Variability and Using the Variation Block Variation Block Structure definitions (dvth0_loc and du0_loc) are adjusted for device size using function3 and function4, and result then in the variations dvth0_geo and du0_geo applied to the model parameters vth0 and u0. While this use model is supported, it is not desirable because it leads to one model per device, which is inefficient in terms of memory. Variations of Element Parameters Devices are not only affected by variations in the underlying model parameters, but also through variations of properties specified at instantiation of an element, or variations on implied properties, such as local temperature. Also, early in the design phase, passive devices sometimes have only a nominal value, but no model as yet because no decision has been made on a specific implementation. For these elements, variations can be specified on the implicit value parameter; for example: R1 1 0 1k. Variations on element parameters are only supported for Local Variations; they are defined in a section within the Local Variation subblock. Element parameter Variations are described with the following syntax: Element_Type Element_Parameter = ’Expression for Sigma’ The syntax Element_Parameter = ’Expression for Sigma’ is shorthand notation for: Variation_in_Element_Parameter = Expression for Sigma If the expression references only constants and parameters that evaluate to constants, then a Gaussian variation with zero mean and a sigma equal to the expression is automatically implied. To describe variation as a function of previously defined independent random variables, use the construct Perturb(), with the following syntax: Element_Type Element_Parameter = Perturb(Expression) The expressions may need to be enclosed in quotes, see the general HSPICE rules for Using Algebraic Expressions on page 278. See Parameters and Expressions on page 49 for limitations. The following lines define a normal distribution with sigma of 10 on the resistors without model: .Element_Variation R R=10 .End_Element_Variation 524 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 20: Analyzing Variability and Using the Variation Block Variation Block Structure In the following example, only resistor ra2 is affected by the temperature variation specified with a uniform distribution from 0 to 10 degrees (the resistor is located next to a power device). ra1 1 0 1k rb1 2 0 1k ra2 3 0 rpoly l=10u w=1u rb2 4 0 rpoly l=10u w=1u .model rpoly r rsh=100 tc1=0.01 .Variation .Local_Variation .Element_Variation Parameter tempvar=U() R(Element_Name~='ra*' && Model_Name~='rpoly') + dtemp=perturb('10*tempvar+5') .End_Element_Variation .End_Local_Variation .End_Variation Because different classes of devices might be affected differently, a selection mechanism based on element name and model name is provided by using a condition clause: Element_Type(condition_clause) Element_Parameter= 'Expression for Sigma' The condition clause allows for specifying variations on selected elements, according to their name or associated model. Wildcard substitutions can be indicated as “?” for single character and “*” for multiple characters. Examples for condition clause syntax are: Element_Type(model_name~='modelNameA') Element_Type(element_name~='elNameB') Element_Type(model_name~='modelNameC' OPERATOR element_name~='elNameD') par='exp' Element_Type(model_name~='modelNameE' OPERATOR model_name~='modelNameF') par='exp' Element_Type(element_name~='elNameG' OPERATOR element_name~='elNameH') par='exp' Where OPERATOR can be && (AND), || (OR). The operator “~=” stands for “matches”. All pattern matching operations are case-insensitive. A leading subcircuit prefix is ignored when matching the element name. HSPICE® User Guide: Simulation and Analysis B-2008.09 525 Chapter 20: Analyzing Variability and Using the Variation Block Variation Block Structure Example In this example, only resistor ra1 varies. ra1 1 0 1k rb1 2 0 1k .Variation .Local_Variation .Element_Variation R(element_name~='ra*') R=20 .End_Element_Variation .End_Local_Variation .End_Variation Supported element types and their parameters are: Table 61 Supported elements and parameters Element Parameter M DTEMP R Rval* DTEMP C Cval* DTEM Q AREA DTEMP D DTEMP L Lval* DTEMP I DCval* mag phase V DCval* mag phase The asterisk “*” denotes implicit value parameter. The DTEMP parameter is implicit; it does not have to be specified on the element instantiation line. 526 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 20: Analyzing Variability and Using the Variation Block Variation Block Structure Example for Voltage Source Netlist element: V1 1 0 0.1 AC Variation definition: V DC=5% (5% of 0.1) V MAG=5% (5% of 1) V PHASE=5 (5 degrees) Access Functions Certain variations depend on element geometry, as defined with parameters at instantiation. The access function (only supported for the Variation Block) Get_E() allows for accessing these parameters in expressions by using the following syntax: Get_E(Element_Parameter) Where Element_Parameter is the name of an element parameter, which must be defined on the instantiation line (except for the DTEMP parameter and the multiplier M). This access function is generally used for specifying variations as a function of device geometry. The Get_E() access function reports the effective device geometry, after resolving parameters, scales and adjustments by process parameters, such as, xw, xl, wint, lint. Refer to the HSPICE Reference Manual: MOSFET Models for equations which depend on the LEVEL of interest and Geometric Scaling for Diode Models in the HSPICE Reference Manual: Device and Element Models for scaling equations. For example, the local variation on the threshold is often specified as inversely proportional to the square root of the total area of the device, as calculated from the product of the element parameters W, L, and M. Nmos nch vth0='1.234e-9/sqrt(Get_E(W)*Get_E(L)*Get_E(M))' Another function allows for accessing the values of global parameters by using the following syntax: Get_P(Global_Parameter) The parameter value is taken from the circuit context: from the subcircuit, if defined inside, otherwise from the top level. In the following example, the resistor variation is determined by sweep parameter “tol”: HSPICE® User Guide: Simulation and Analysis B-2008.09 527 Chapter 20: Analyzing Variability and Using the Variation Block Variation Block Structure .param tol=1 ra1 1 0 1k i1 0 1 1m .Variation .Local_Variation .Element_Variation R R='get_P(tol)' % .End_Element_Variation .End_Local_Variation .End_Variation .dc tol 1 5 1 monte=100 If a variation must be expressed as a function of a simulator option (specified as .option=optionval outside of the Variation Block), the access function Get_O is available, using the construct Get_O(option_name). For example, if the element parameter nf (number of fingers) is used with some advanced models, the device width reported by the Get_E function depends on the value of .OPTION WNFLAG. For variation as a function of total device area, the following definition produces the expected results, independent of the settings of WNFLAG: vth0 = `6.0621e-9/sqrt(Get_E(W)*Get_E(L)*Get_E(M)*\\ (1-Get_O(WNFLAG)+Get_O(WNFLAG)*get_E(NF)))' Spatial Variation To make the Spatial Variation useful, the simulator needs to know the coordinate of a particular device. The element instantiation must therefore be extended to include placement information. For example, for an MOS device: Mid Dn Gn Sn Bn ModelName w=width l=length x=xcoor y=ycoor In the Spatial Variation definition, the element coordinates are accessed using the Get_E() function. For the current release, HSPICE supports only netlists with a single subcircuit, with devices on the top level and/or in the subcircuit. All devices of the model which has Spatial Variation defined, must have coordinates, and these must be specified with numbers (no parameters allowed). 528 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 20: Analyzing Variability and Using the Variation Block Variation Block Examples Special Rules Regarding Variation Block Usage The contents of the Variation Block are generally created by a foundry. To safeguard against unintentional overwriting of these variation definitions, two features are in place: ■ The name-space of the Variation Block is separate from the netlist contents. ■ Once a variation is specified on a parameter, it can not be redefined later, even in .ALTER statements. For example, if a user wants to change the corners defined in a model library file with an .ALTER statement, then the Variation Block must be specified in a separate *.lib section. Variation Block Examples This simple Variation Block is used in the example netlists opampdcm.sp and opampmc.sp which are available in the HSPICE demo directory: \$installdir/demo/hspice/variability The following variations are defined in the example: Global Variations on vth0 (absolute) Global Variations on u0 (relative) Local Variations on vth0 (absolute), as a function of device area Local Variations on u0 (relative), as a function of device area Local Variation on the implicit value of resistors (relative) .Variation .Global_Variation Nmos snps20N vth0=0.07 u0=10 % Pmos snps20P vth0=0.08 u0=8 % .End_Global_Variation .Local_Variation Nmos snps20N vth0='1.234e-9/ sqrt(Get_E(W)*get_E(L)*Get_E(M))' + u0='2.345e-6/sqrt(get_E(W)*get_E(L)*get_E(M))' % Pmos snps20P vth0='1.234e-9/ sqrt(Get_E(W)*get_E(L)*Get_E(M))' + u0='2.345e-6/sqrt(Get_E(W)*get_E(L)*get_E(M))' % .Element_Variation R r=10 % .End_Element_Variation .End_Local_Variation .End_Variation HSPICE® User Guide: Simulation and Analysis B-2008.09 529 Chapter 20: Analyzing Variability and Using the Variation Block Variation Block Examples Principal Component-based Global Variation Modeling In this example, the independent random variables A1, A2, and A3 are the principal components, on which all variations (nmos and pmos) are modeled. See [1] for details. .Global_Variation Parameter A1=N() A2=N() A3=N() Nmos nch + tox =Perturb('-6.2E-12*A1-8.1E-12*A2-2.7E-12*A3') + vth0=Perturb('-3.6E-03*A1+8.9E-03*A2-1.5E-03*A3') + cjn =Perturb('-3.2E-06*A1+6.7E-06*A2-4.3E-06*A3') + u0 =Perturb(' 5.6E-04*A1-9.7E-04*A2+7.6E-04*A3') + .... Pmos pch + tox =Perturb('-7.5E-12*A1-6.9E-12*A2-8.8E-12*A3') + vth0=Perturb('-7.4E-03*A1+3.3E-03*A2-7.2E-03*A3') + cjn =Perturb('-5.0E-06*A1+8.9E-06*A2-3.2E-06*A3') + u0 =Perturb(' 7.6E-04*A1-4.3E-04*A2+4.8E-04*A3') + .... .End_Global_Variation Local Variation Example for Submicron Technology This Local Variation data was created using the methodology outlined in [2]. Note the different dependencies on w and l for the different parameters. .Local_Variation Nmos nch + tox ='3.1e-07/sqrt(Get_E(L)*Get_E(W)*Get_E(M))' % + wint ='6.2e-12/sqrt(Get_E(L)*Get_E(M))' + lint ='2.0e-12/sqrt(Get_E(W)*Get_E(M))' + nch ='1.9e-06/sqrt(Get_E(L)*Get_E(W)*Get_E(M))' % .End_Local_Variation Spatial Variation Example .Variation .Spatial_Variation Parameter a = N( ) Parameter b = U( ) Parameter Pi = 3.14159265 Parameter Angle = 'Pi*2*b' NMOS snps20n + vth0 = Perturb('20*a*sqrt(Get_E(x)* Get_E(x)+ Get_E(y)* Get_E(y)) \\ *cos(Angle-atan(Get_E(y)/Get_E(x))-Get_E(x)<0?Pi:0))') .End_Spatial_Variation .End_Variation 530 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 20: Analyzing Variability and Using the Variation Block Group Operator {...} and Subexpressions The Spatial Variation is specified as a plane with a slope sigma of 20mV/mm, and arbitrary rotation on the chip surface. Group Operator {...} and Subexpressions To improve readability of complex variation specifications, a group operator {...} and subexpressions are available. Used within a defined group, subexpressions can reference element and global parameters. (As an efficient alternative, consider using the Common Model Interface (CMI). Consult your HSPICE technical support team for application note and source code access.) Syntax ModelType ModelName { Parameter ... ModelParameter= ... } The group operator {...} separates variation definitions group by group. Each group is based on one model, which means all parameters defined inside a group operator are specific to this model. A group definition starts after the Model Name, and must end after the last model parameter specification of the same Model Name. Parameter definitions support expressions with Get_E() or Get_P(). ModelParameter definitions have no leading Parameter key. Syntax Extension with Bins ModelType ModelName { Parameter ... ModelParameter= ... ModelName.1 ModelParameter= ... ........ ModelName.m ModelParameter= ... } Model parameter definitions within a group before the first bin name (ModelName.1 in the example) apply to all bins; whereas the following definition is bin specific: HSPICE® User Guide: Simulation and Analysis B-2008.09 531 Chapter 20: Analyzing Variability and Using the Variation Block Group Operator {...} and Subexpressions ModelName.1 ModelParameter= ... Example In this example, note that the expressions before NMOS apply to all bins, whereas those for mn.12 are bin specific. .Global_Variation Parameter PG1=N() PG2=N() PG3=N() + dxl=' 4.3e-9 * PG1 ' + dvth0='0.02 * (-0.29 * PG1 + 0.95 * PG2)' + dtoxe='1.3e-10 * (0.39 * PG1 -0.87 * PG2 + 0.28 * PG3)' + F1='1.0/(2*SQRT(dvth0*dvth0))' + F_FF='(-dvth0+SQRT(dvth0*dvth0))*F1' + F_SS='(dvth0+SQRT(dvth0*dvth0))*F1' NMOS mn.12 { parameter u0varg='-dvth0*(F_FF*2.1+F_SS*0.6)' xl= perturb(dxl) vth0=perturb(dvth0) lvth0=perturb(dvth0*(F_FF*0.097+F_SS*0.054)) u0=perturb('u0varg') % wu0=perturb('u0varg') % lu0=perturb('u0varg') % pu0=perturb('u0varg') % toxe=perturb(dtoxe) toxp=perturb(dtoxe) } .End_Global_Variation .Local_Variation NMOS mn.12 { parameter sqrtarea='SQRT(get_E(W)*get_E(L)*get_E(M)' vth0='1.2e-9/sqrtarea' u0='2.3e-6/sqrtarea' } .End_Local_Variation Rules for Using the Group Operator The following rules apply when using the block operator: ■ ■ Condition clauses are not supported inside of a group. ■ Any specifications that appear at the same line and after the opening '{' are ignored; a parameter definition should begin at a new line after the bracket. ■ Group operators only support model parameter, not subcircuit parameter definitions. ■ 532 Independent random variables can not be defined inside of a group. A group with the same ModelType and ModelName can be defined only once; HSPICE will abort if any duplicated group definitions are found. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 20: Analyzing Variability and Using the Variation Block Interconnect Variation in Star-RCXT with the HSPICE Flow Parameter Hierarchies Succession relations between parameters defined inside and outside of a group have the following restrictions: parameters defined inside a group can not conflict with those defined outside of it. However, the same parameter can be redefined inside another group, and these are invisible to each other. The parameter hierarchies are as follows: .Param a=2 Defined outside of Variation Block; can be referenced using get_P() syntax .Variation parameter a=3 .Global_Variation parameter b='a*get_P(a)' Global parameter within Variation Block; can be used in all subblocks b = 6; valid in global variation subblock NMOS nch { parameter c=0.4*b c = 2.4; only visible in this group; .... can be redefined in other groups } PMOS pch { parameter c='-0.3*b' c = -1.8; c is only visible in this group; .... can be redefined in other groups } .End_Global_Variation .Local_Variation parameter b='2*a*get_P(a)' b=12; valid in local variation subblock .Element_Variation R r='0.1*b' % Relative sigma of r is 0.1*2*2*3*0.01=0.012 .End_Element_Variation .End_Local_Variation .End_Variation Interconnect Variation in Star-RCXT with the HSPICE Flow In its Z-2006.12 release, the Synopsys layout extraction tool, Star-RCXT, established a Sensitivity-Based Extraction Flow, which can generate a variation-aware netlist to interpret and produce simulation results based on the HSPICE® User Guide: Simulation and Analysis B-2008.09 533 Chapter 20: Analyzing Variability and Using the Variation Block Interconnect Variation in Star-RCXT with the HSPICE Flow probability distribution of interconnect variations. The currently available methodology of running worst case corners produces pessimistic results, as opposed to the new method, which calculates the actual distribution, and which then allows for selecting design limits based on yield. Using the Sensitivity-Based Extraction Flow, Star-RCXT extracts resistors and capacitors associated with the interconnect. HSPICE then works as a postprocessor to do statistical analysis with the output file from Star-RCXT which contains sensitivity information that is required to support Variation Blockbased ACMatch, DCMatch, and Monte Carlo analyses. Refer to the Star-RCXT User Guide, Chapter 11: Variation-Aware Extraction for more information. Variation Block and Statistical Sensitivity Coefficients Statistical sensitivity coefficients corresponding to each parasitic value are generated and provided by Star-RCXT. These coefficients measure the expected change in the capacitance/resistance due to the variation of an interconnect process parameter. By definition, the fractional change of capacitance/resistance value due to a unit variation in a specific parameter is the statistical sensitivity of the capacitance/resistance in question with respect to that parameter. The combination of the nominal capacitance/resistance tables, and the corresponding statistical sensitivity coefficients, provides the necessary and sufficient coverage for all possible effects of parameter variations on capacitance/resistance. This eliminates the need for using extensive sets of capacitance tables, and provides a realistic coverage of all possible ranges of random variation. Application of statistical sensitivity coefficients requires that the parameter variations be small. This restriction is acceptable for nanometer semiconductor processes since a large part of the process variation tends to be systematic and is considered and modeled under the scope of deterministic process variation. Given the distribution of parameter variations, based on statistical sensitivity information, you can get the statistical effects on capacitance and resistance values in Monte Carlo, DCMatch, and ACMatch analyses. Interconnect variability is defined in its own block, the Interconnect_Variation subblock. Currently, the variation is restricted to the global level. The Interconnect_Variation subblock is created by Star-RCXT and is included as part of the post-layout netlist. 534 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 20: Analyzing Variability and Using the Variation Block Interconnect Variation in Star-RCXT with the HSPICE Flow Usage Example and Input Syntax 1: Interconnect Variation Block The information in the Variation Parameters section is re-coded as follows: .Variation .Interconnect_Variation .Global_Variation ID= param_id Name = param_name [R_Sensitivity_Type = + param_type] [C_Sensitivity_Type = param_type] [L_Sensitivity_Type = param_type] [K_Sensitivity_Type = + param_type] [CV= coeff_of_var] ... .End_Global_Variation .End_Interconnect_Variation .End_Variation Argument Description param_id Is a nonnegative integer to uniquely identify the parameter. In this way, every parameter is associated with a different integer. These unique identifiers are used in the parasitic section to represent the sensitivity information. param_name Are alphanumeric characters without any spaces or meta characters. param_type Valid values are N, D, or X. These refer to the form of the sensitivity expression and indicate if the particular parameter variation appears in the numerator, the denominator, or does not influence the element value. If not specified, the default is X. coeff_of_var This argument is numeric and optional. The default value is 1. Variation blocks have global scope and the above definition should appear outside any subcircuit definitions. R_Sensitivity_Type, L_Sensitivity_Type, and K_Sensitivity_Type help to define the form of the sensitivity expression. This is a generalization of the Taylor series-based HSPICE® User Guide: Simulation and Analysis B-2008.09 535 Chapter 20: Analyzing Variability and Using the Variation Block Interconnect Variation in Star-RCXT with the HSPICE Flow variation form, 1 + ∑si Δ pi , to the more general Pade ′ iε I 1 + ∑i Δ pi s approximation: --------------------------- . 1 + ∑s j Δ p j jε J The index sets I and J are disjoint, for example, a parameter can influence either the numerator or the denominator, but not both. In the Star-RCXT-VX and HSPICE releases, only resistors have the more general Pade ′ form, capacitors have the Taylor series form, and inductors (normal and K-Matrix style) have no variation. Example of the extended NETNAME-style information .Variation .Interconnect_Variation .Global_Variation ID=0 Name=ME1_T R_Sensitvity_Type=D CV=0.06 ID=1 Name=ME1_W R_Sensitvity_Type=D CV=0.04 ID=2 Name=ME1_R R_Sensitvity_Type=N CV=0.05 ID=3 Name=ME12_T R_Sensitvity_Type=D CV=0.06 ID=4 Name=ME12_ER R_Sensitvity_Type=X CV=0.02 ID=5 Name=ME2_T R_Sensitvity_Type=D CV=0.08 ID=6 Name=ME2_W R_Sensitvity_Type=D CV=0.07 ID=7 Name=ME2_R R_Sensitvity_Type=N CV=0.04 ID=8 Name=ME23_T R_Sensitvity_Type=D CV=0.054 ID=9 Name=ME23_ER R_Sensitvity_Type=X CV=0.02 ID=10 Name=ME3_T R_Sensitvity_Type=D CV=0.08 ID=11 Name=ME3_W R_Sensitvity_Type=D CV=0.07 ID=12 Name=ME3_R R_Sensitvity_Type=N CV=0.04 .End_Global_Variation .End_Interconnect_Variation .End_Variation 536 C_Sensitvity_Type=N C_Sensitvity_Type=N C_Sensitvity_Type=X C_Sensitvity_Type=N C_Sensitvity_Type=N C_Sensitvity_Type=N C_Sensitvity_Type=N C_Sensitvity_Type=X C_Sensitvity_Type=N C_Sensitvity_Type=N C_Sensitvity_Type=N C_Sensitvity_Type=N C_Sensitvity_Type=X HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 20: Analyzing Variability and Using the Variation Block Interconnect Variation in Star-RCXT with the HSPICE Flow In the example above, ■ The ID field must be a non-negative integer. HSPICE uses the ID field to link variation information to the sensitivity in the C and R records. ■ The Name field is alphanumeric and should not contain any white space or meta characters. The Name field is used only for output annotation. ■ The CV field is numeric and the CV field is interpreted as the standard deviation for a (default) normal distribution. 2: Model Card in the Header Section The purpose of the model card in the header section is to communicate to HSPICE the model name used in the parasitic section for the resistors as well as the reference temperature. The reference temperature is equal to the GLOBAL_TEMPERATURE in ITF with units in celsius. Syntax .model <model_name> R Tref=<global_temperature> Example .model resStar R Tref=25 3: Parasitic Section The resistance and capacitance records take the form: Cxxx <node1> <node2> Value SENS [param_id, param_id, …]= [sens_coeff, sens_coeff, …] Rxxx <node1> <node2> <model_name> R=<value> TC1=<val> TC2=<val> SENS [param_id, param_id, …] = [sens_coeff, sens_coeff, …] ........ Examples The following is an example of a C record in NETNAME format: C1 G2[21]:F12 Y2:897 0.699 Sens [0,1,5,6] = [0.009,0.001,0.006,0.010] C2 X3:962 RX[12]:F74 0.324 Sens [0,1,5,8] = [0.010,0.006,0.017,-0.003] The following is an example of an R record in NETNAME format: R1 G2[21]:F12 G2[21]:8 resStar R=0.699 TC1=0.0023 TC2=4e-7 Sens [5,6,7] = [0.51,0.64,0.86] HSPICE® User Guide: Simulation and Analysis B-2008.09 537 Chapter 20: Analyzing Variability and Using the Variation Block Control Options and Syntax The Sens key defines the start of sensitivity information and the two vectors are the sparse sensitivity indices and the corresponding values. The first vector may contain only ordered non-negative integers that map to the Interconnect_Variation section, while the second vector of real numbers is interpreted as the sensitivities. The lengths of the two vectors must match. There must be one blank space between the Sens keyword and the sensitivity indices. Note: For interconnect output, see Interconnect Output Formats in Chapter 21, Monte Carlo Analysis Using the Variation Block Flow. Control Options and Syntax Options can be specified, one per logical record in a Variation Block. Several of the listed options are useful if a Variation Block is part of a model file that a designer cannot edit. However, you can add a Variation Block with options to control how the contents of all Variation Blocks are used in the analysis. For Monte Carlo-specific options: see Chapter 21, Monte Carlo Analysis Using the Variation Block Flow. Note: No period is required before the word Option in the Variation Block, and is, in fact, illegal. The following options can be specified within the Variation Block: ■ Option Normal_Limit=Value Limits the range of the Normal distributions. The default value is 4, i.e., numbers in the range +/- 4 σ are generated. The range allowed is 0.1 to 6.0. This option allows a foundry to limit the perturbations to parameter ranges where a model is still valid. ■ 538 Option Ignore_Variation_Block=Yes Ignores the Variation Block and executes earlier style variations (traditional Monte Carlo analysis). By default, the contents of the variation block are executed and other definitions (AGAUSS, GAUSS, AUNIF, UNIF, LOT, and DEV) are ignored. Previous methods of specifying variations on parameters and models are not compatible with the Variation Block. By default, the contents of the Variation Block are used and all other specifications are ignored. Thus no changes are required in existing netlists other than adding the Variation Block. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 20: Analyzing Variability and Using the Variation Block Control Options and Syntax ■ Option Ignore_Local_Variation=Yes Excludes effects of local variations in simulation. Default is No. ■ Option Ignore_Global_Variation=Yes Excludes effects of global variations in simulation. Default is No. ■ Option Ignore_Spatial_Variation=Yes Excludes effects of spatial variations in simulation. Default is No. ■ Option Ignore_Interconnect_Variation=Yes Excludes effects of interconnect variations in simulation. Default is No. (See Interconnect Variation in Star-RCXT with the HSPICE Flow.) ■ Option Output_Sigma_Value=Value Use to specify the sigma value of the results of Monte Carlo, DCMatch, and ACMatch analyses. Default is 1, range is 1 to 10. Note that this option only changes the output listings and that the input sigma is not affected. ■ Option Vary_Only Subckts=SubcktList Use either this option to limit variation to the specified subcircuits or the following option, but not both. Actual subcircuit names are specified here (not the hierarchical names). ■ Option Do_Not_Vary Subckts=SubcktList Excludes variation on the specified subcircuits. Use either this option to limit variation to the specified subcircuits or the one above, but not both. Actual subcircuit names are specified here (not the hierarchical names). HSPICE® User Guide: Simulation and Analysis B-2008.09 539 Chapter 20: Analyzing Variability and Using the Variation Block References References [1] K. Singhal and V. Visvanathan: Statistical device models from worst case files and electrical test data. IEEE Trans. Semiconductor Manufacturing, November 1999. (Global variation modeling by principal components) [2] P.G. Drennan and C.C. McAndrew: Understanding MOSFET mismatch for analog design. IEEE J. Solid-State Circuits, March 2003. (Modeling mismatch in nanometer technologies) 540 HSPICE® User Guide: Simulation and Analysis B-2008.09 21 21 Monte Carlo Analysis Using the Variation Block Flow Describes enhanced Monte Carlo analysis in HSPICE. These topics are covered in the following sections: ■ Overview ■ Monte Carlo Analysis in HSPICE ■ Sampling Options ■ Application Considerations Known Limitations ■ Troubleshooting Monte Carlo Issues Overview Monte Carlo analysis is the generic tool for simulating the effects of variations in device characteristics on circuit performance. The variations in device characteristics are expressed as distributions on the underlying model parameters. For each sample of the Monte Carlo analysis, random values are assigned to these parameters and a complete simulation is executed, producing one or more measurement results. The series of results from a particular measurement represent a distribution, which can be characterized by statistical terms; for example, mean value and standard deviation (σ). With increasing number of samples, the shape of the distribution gets better defined with the effect that the two quantities converge to their final values. A standard way of analyzing the results is by arranging them in bins. Each bin represents how many results fall into a certain range (slice) of the overall distribution. A plot of these bins is a histogram, which shows the shape of the distribution as the number of results versus slice. As the number of samples increases, the shape of the histogram gets smoother. HSPICE® User Guide: Simulation and Analysis B-2008.09 541 Chapter 21: Monte Carlo Analysis Using the Variation Block Flow Overview The ultimate interest of Monte Carlo simulation is to find out how the distribution in circuit response relates to the specification. The aspect of yield is considered here: ■ What is the percentage of devices which meet the specification? ■ Is the design centered with respect to the specification? Closely related is the aspect of over-design. This is when the circuit characteristics are within specification with a wide margin, which could be at the expense of area or power and ultimately cost. A typical design process is iterative, first for finding a solution which meets the nominal specification, and then moving on to a solution that meets yield and economic constraints, including the effects of variations in device characteristics. In this optimization process, it helps to understand the relationship of the design parameters to the circuit response, and the relationships of the different types of circuit response. This information is available after running Monte Carlo analysis and can best be presented by Pairs Plots. This is a matrix of two-dimensional plots for investigating pair-wise relationships and exploring the data interactively. HSPICE does not produce such plots, but makes the necessary data available from Monte Carlo simulation. Figure 93 shows an example of a Pairs Plot from a simple resistive divider: Figure 93 542 Pairs Plot example HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 21: Monte Carlo Analysis Using the Variation Block Flow Monte Carlo Analysis in HSPICE An application note, “Pairs Plots from HSPICE Monte Carlo,” describes the basic ideas and includes a MATLAB® script to create such a plot. Contact the Synopsys Support Center for a copy of the application note. Monte Carlo analysis is computationally expensive; therefore, other types of analysis have been created that produce certain results more efficiently. For cases where only the effects of variations on the DC or AC response of a circuit is of interest, methods called DCMatch and ACMatch analyses can be used; for a description, see Chapter 22, Mismatch Analyses. Monte Carlo Analysis in HSPICE Monte Carlo analysis has been available in HSPICE for some time and is based on two approaches: ■ defining distributions on global parameters (using AGAUSS, GAUSS, UNIF, and AUNIF) in a netlist; for example, .param var=agauss(20,1.2,3) ■ defining distributions on model parameters using DEV and LOT constructs in a model file; for example, vth0=0.6 lot/0.1 dev/0.02 The above two methods are documented in Appendix A, Statistical Analysis. To satisfy some key requirements for modern semiconductor technologies, a new approach is available based on the Variation Block, which is described in detail in Chapter 20, Analyzing Variability and Using the Variation Block. This new approach is not compatible with the earlier ones; see the first option in Monte Carlo-Specific Variation Block Options on page 546 for ways to select one or the other method. Figure 94 on page 544 shows the Monte Carlo simulation flow when global and local variations are specified. Sample number 1 of a Monte Carlo analysis is always executed with nominal values and no variation. For subsequent samples, HSPICE updates the parameters specified for variation in the variation block with random values. For global variations, a specified parameter is changed by the same random value for all elements that share a common model. For local variation, the specified parameter is changed by a different random value for each element. The changes due to global and local variations are additive and are saved in a file for post-processing. When all the elements have been updated, the simulation is executed and the measurement results HSPICE® User Guide: Simulation and Analysis B-2008.09 543 Chapter 21: Monte Carlo Analysis Using the Variation Block Flow Monte Carlo Analysis in HSPICE are saved. When all the requested samples have been simulated, HSPICE calculates the statistics of the measurement results and includes them in the run listing. Start Index 1: Simulate with nominal parameters Global variation: Add some random value to particular parameter for all devices Local variation: Add different random value to specified parameters for each device Index n: Simulate with variations applied More Done Calculate statistics End Figure 94 Monte Carlo analysis flow in HSPICE Input Syntax Monte Carlo analysis is always executed in conjunction with another analysis (see Traditional Monte Carlo Analysis in Appendix A for full discussion): 544 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 21: Monte Carlo Analysis Using the Variation Block Flow Monte Carlo Analysis in HSPICE .DC sweepVar start stop step [SWEEP MONTE=MCCommand] .AC type step start stop [SWEEP MONTE=MCcommand] .TRAN step start stop [SWEEP MONTE=MCCommand] Syntax for MCcommand: MONTE=val|list(num)|valfirstrun=num| + list(<num1:num2><num3><num4:num5) Parameter Description val Specifies the number of random samples to produce. val firstrun=num Specifies the sample number on which the simulation starts. list (num) Specifies the sample number to execute. list(<num1:num2><num3> <num4:num5>) Samples from num1 to num2, sample num3, and samples from num4 to num5 are executed (parentheses are optional). The parameter values and results are always the same for a particular sample, whether generated in one pass or using firstrun or the list syntax. Therefore, Monte Carlo analyses can be split or distributed and the results spliced together with scripts. DC Sweep Examples In these examples a DC sweep is applied to a parameter k. In the first case, 10 samples are produced. In the second case, five samples are produced, starting with sample number 6. In the last two examples, samples 5, 6, 7 and 10 are simulated. .dc k start=2 stop=4 step=0.5 monte=10 .dc k start=2 stop=4 step=0.5 monte=5 firstrun=6 .dc k start=2 stop=4 step=0.5 monte=list (5:7 10) HSPICE® User Guide: Simulation and Analysis B-2008.09 545 Chapter 21: Monte Carlo Analysis Using the Variation Block Flow Monte Carlo Analysis in HSPICE Monte Carlo-Specific Variation Block Options Options for the deprecated Monte Carlo style are ignored when simulations based on the Variation Block are executed. The options described in Chapter 19 (Control Options and Syntax) control Monte Carlo analysis. In addition, the following Monte Carlo-specific options can be specified in the first section of the Variation Block: ■ Option Random_Generator = [Default | MSG] Specifies the random number generator used in Variation Block based Monte Carlo analysis. Random_Generator=MSG invokes the generator from previous releases. Random_Generator=Default uses a longer cycle generator. ■ Option Stream =[x | Random | Default] Specifies an integer stream number for random number generator (only for Variation Block). The minimum value of x is 1, the maximum value of x is 20; If Stream=Random, HSPICE creates a random stream number between 1 and 20 according to the system clock, and prints it in the .lis file for the user to debug. If Stream=Default, then it is equivalent to Stream=1. ■ Option Normal_Limit=Value Limits the range for the numbers generated by the random number generator for Normal distributions. The default value is 4, i.e., numbers in the range +/- 4 σ are generated. The range allowed is 0.1 to 6.0. ■ Option Output_Sigma_Value=Value Specifies the sigma value of the results. Default is 1, range is 1 to 10. Note that the input sigma is not affected. ■ Option Print_Only Subckts=SubcktList Use either this option to limit output in the .mc# file to the specified subcircuits or the following one, but not both. Actual subcircuit names are specified here (not the hierarchical names). ■ Option Do_Not_Print Subckts=SubcktList Use either this option to exclude output from the specified subcircuits to the .mc# file or the one above, but not both. Actual subcircuit names are specified here (not the hierarchical names). 546 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 21: Monte Carlo Analysis Using the Variation Block Flow Output Example for Ignore_Global and Normal_Limit Options In the following example, global variations are not simulated, and the Normal distributions are exercised to 6σ. For information regarding Local and Global Variations, see Subblocks for Global, Local and Spatial Variations in the chapter Analyzing Variability and Using the Variation Block. .Variation Option Ignore_Global_Variation=Yes Option Normal_limit=6 .Global_Variation Definitions for global variations .End_Global_Variation .Local_Variation Definitions for local variations .End_Local_Variation .End_Variation Output Simulation Listing The output listing file contains a summary of the names of all input parameters that are subject to global or local variations. For each sample, the measured results are printed. Finally, the statistics for the measured data are reported. Example: Output Listing Partial printout of an output listing: HSPICE® User Guide: Simulation and Analysis B-2008.09 547 Chapter 21: Monte Carlo Analysis Using the Variation Block Flow Output MONTE CARLO DEFINITIONS Random number generator is default, and stream = 1 Global variations: model parameter snps20n vth0 snps20n u0 Local variations: model snps20n snps20n parameter vth0 u0 Element variations: element r1 parameter r *** monte carlo index = systoffset1= 1.3997E-03 *** monte carlo index = systoffset1= -9.2694E-04 1 *** 2 *** MONTE CARLO STATISTICS meas_variable = systoffset mean = 1.4398m varian sigma = 1.1132m avgdev max = 5.3035m min 1-sigma = 1.1132m median = 1.2391u = 893.3815u = -1.4532m = 1.4184m Measurement Output File Measure commands cause simulation results to be saved for each sample, along with its index number. Depending on the analysis type, the name of the result file has an extension of ms#, ma#, or mt#, where the # denotes the regular sequence number for HSPICE output files. The changes in all parameter values subject to variation are saved in a file with an extension of .mcs#, .mca#, or .mct#, depending on the analysis type. Parameter File The structure of this file is the same as for regular measure files. Therefore, the data can be read with the same post-processing tools (for example, CosmosScope). In the header section, the names of the parameters and independent variables are presented as follows: ■ ■ for local variation on model parameter: Element_Name@Model_Name@Parameter_Name@ID ■ 548 for global variation on model parameter: Model_Name@Parameter_Name@ID for local variation on element parameter: Element_Name@Parameter_Name@ID HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 21: Monte Carlo Analysis Using the Variation Block Flow Output ■ for interconnect variation: Param_Name@ID and Element_Name@ID ■ for independent variables: Variable_Name@ID where: ID is a three-character string for identifying the type of the parameter as follows. Table 62 and Table 63 on page 549 list the independent and dependent parameter types, respectively. Table 62 Independent Parameter Type Identifier First character Second character Third character I G Global N Normal distribution L Local U Uniform distribution S Spatial C CDF distribution Independent variable Table 63 Dependent Parameter Type Identifier First character Second character Third character M Model G Global R Relative E Element L Local A Absolute S Subcircuit Variables S Spatial T Interconnect The independent variables include explicitly specified random variables [for example: A=N()], and the internally generated random variables for implicit definitions in the expressions for sigma (for example: Nmos snps20 vth0=0.07). Values for parameters that have absolute variation specified in the variation block are reported as absolute deviation from the nominal value. Values for parameters that have relative variation specified are reported as a relative deviation in percent. The printed value for parameter “status” is “1” for a successful simulation, and “0” for a failed simulation. If the netlist or the model or both are encrypted, hash codes are printed in the appropriate places, which are meaningful to HSPICE for External Sampling. HSPICE® User Guide: Simulation and Analysis B-2008.09 549 Chapter 21: Monte Carlo Analysis Using the Variation Block Flow Output Example: mcs# File index 1.0000 2.0000 snps20n@vth0@IGN snps20n@u0@IGN snps20n@vth0@MGA snps20n@u0@MGR xi82.mn6@snps20n@vth0@MLA xi82.mn6@snps20n@u0@MLR xi82.mn1@vth0@ILN xi82.mn1@u0@ILN xi82.mn1@snps20n@vth0@MLA xi82.mn1@snps20n@u0@MLR xi82.mn2@vth0@ILN xi82.mn2@u0@ILN xi82.mn2@snps20n@vth0@MLA xi82.mn2@snps20n@u0@MLR xi82.rcomp@r@ILN xi82.rcomp@r@ELR status alter# 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 1.0 1.0000 0.6141 0.6284 4.299e-02 6.284e-02 2.1837 0.2184 1.7554 0.1755 1.6017 0.1602 0.4769 4.769e-02 -1.0088 0.5350 In this example, the changes due to the global variations on parameters vth0 (absolute) and u0 (relative) are reported first, then the changes on each device due to local variations on the same parameters are reported next, and finally, the local variation on the parameter r of the element rcomp are reported. Note that the parameter value applied to the device for a particular sample is the nominal value, plus the reported change due to global variations, plus the reported change due to local variations, and so on. The contents of this parameter file are useful for data mining. In connection with the measured data in the regular output file, the relationship of circuit response variation to parameter variation can be investigated by using, for example, a Pairs Plot as shown in Figure 93 on page 542. Note: The contents of this file are subject to change. Interconnect Output Formats The following is example output for interconnect variation testing. In the Monte Carlo sampling output file *.mc?#, one identifier keyword for interconnect variation parameter is used. In the following, IGN is the extension for 550 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 21: Monte Carlo Analysis Using the Variation Block Flow Sampling Options independent variables. TGA is the extension for dependent variables.The t is present for interconnect parameters: \$ DATA1 SOURCE='HSPICE' VERSION='Y-2006.09' \$ This file format is subject to change .TITLE '* two capacitors for model parameter variation testing' index fox_c_t@IGN fox_a_t@IGN ild_b_t@IGN imd1c_t@IGN imd1d_t@IGN imd2a_t@IGN r1@TGA r2@TGA r11@TGA r22@TGA r211@TGA r222@TGA c1@TGA c2@TGA c11@TGA c22@TGA status alter# 1.0000 0 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 1.0 1.0000 2.0000 3.0000 0.6141 5.198e-02 -1.031e-02 6.133e-05 2.464e-04 5.796e-04 1.0 -0.1087 1.6842 3.551e-03 -2.440e-04 -7.813e-05 1.055e-04 0.6284 1.2452 -3.537e-04 2.464e-03 3.037e-04 0.8866 -1.5600 -5.191e-02 2.964e-03 5.073e-04 1.0000 -0.6694 -1.0088 9.223e-05 -7.813e-04 -2.212e-04 3.363e-02 0.5350 1.782e-02 1.220e-03 5.374e-05 Sampling Options This section presents the advanced sampling methods can be defined in the Variation Block. Factorial Sampling Option Sampling_Method=Factorial HSPICE® User Guide: Simulation and Analysis B-2008.09 551 Chapter 21: Monte Carlo Analysis Using the Variation Block Flow Sampling Options Use this option to evaluate the circuit response at the extremes of variable ranges to get an idea of the worst and best case behavior. The response is evaluated at the center of the hypercube (nominal) and at all its corners in the full factorial sampling method (see Figure 95). There are 1+2m samples for a space with m independent variables. To prevent large runaway jobs, the problem dimension is restricted to m ≤12 which results in ~4K simulations. If the size constraint is violated, then the command is ignored and an error message is generated. 6 5 2 1 4 7 5 4 1 3 8 2 Figure 95 3 2 3 Factorial Hypercube Evaluation at Center and Corners One-Factor-at-a-Time Sampling Option Sampling_Method=OFAT This sampling method varies One-Factor-At-a-Time, a Design of Experiments feature. [1] The number of samples is 2m+1 with m independent variables. The number specified on the Monte Carlo command is ignored, and m must be less than 2500. Sampling starts with no perturbation (nominal), then negative and positive perturbation only on the first parameter, negative and positive perturbation only on the second parameter, etc. The amounts of perturbation are the extreme values for a uniform distribution, and the Normal_Limit values for a normal distribution. Figure 96 illustrates OFAT examples. 5 5 7 2 1 3 2 1 3 1 2 6 4 Figure 96 552 3 4 One-Factor-at-a-Time sampling HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 21: Monte Carlo Analysis Using the Variation Block Flow Sampling Options A suboption, intervals=n, creates 2mn+1 intervals with equal probability. The full syntax is then: Option Sampling_Method=OFAT Intervals=2 9 8 2 3 1 4 5 2 3 1 4 5 7 6 Figure 97 suboption intervals Latin Hypercube Sampling Option Sampling_Method=LHS Latin Hypercube Sampling is an efficient sampling technique for Monte Carlo analysis of systems which are modeled on a computer and that have large numbers of variable parameters. [2] [3] Advantages of LHS are: ■ The estimation error is smaller on most real world problems and a smaller sample size can be used to get the same precision in the results. ■ The sample points are evenly spread over the entire range of variation of each parameter. ■ The circuit is exercised over a wide range of parameter values and will often detect weak spots in the design. ■ You can replicate the sampling using Option Replicates=Value This option runs replicates of the Latin Hypercube samples. The sample with Nominal conditions is simulated once. HSPICE repeats the LHS run the number of times specified by Value. For example, if, in a regular run, you have 10+1 (including nominal value) iterations, if you set Replicates=2, you generate 21 iterations (or 2x +1) Latin Hypercube Sampling. HSPICE® User Guide: Simulation and Analysis B-2008.09 553 Chapter 21: Monte Carlo Analysis Using the Variation Block Flow Sampling Options Figure 98 Example of the distribution of 10 sampling points in two dimensions Note: Monte Carlo options firstrun and list are not supported with LHS. External Sampling You can also execute a dataset of externally created perturbations instead of relying on one of the built-in sampling methods. External sampling allows design and process exploration tools to run statistical experiments, with the variables for each sample under their full control. Usage Model for External Sampling Use the following procedure 1. Execute HSPICE with a regular simulation command (AC, DC, TRAN) and monte=1 to produce a *.mc?0 file, which lists all the independent and dependent variables. 2. Create a data block outside of HSPICE with the desired perturbations on the independent variables, for global and local variations. 3. Run an HSPICE simulation using this externally generated data block content. 4. Repeat Steps 2 and 3, depending on the outcome of the previous experiments. 554 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 21: Monte Carlo Analysis Using the Variation Block Flow Application Considerations Syntax The external sampling feature is defined in two parts in the Variation Block, a data block and the option: .Variation .Data test1 Index p1@IGN 1 .0 2 .0 3 .3 4 .0 5 .0 6 .0 .Enddata snps20p@vth0@ILN .0 0.1086 .0 .0 .0 .0 x1.mn1@q1@ILN .0 .0 .0 1.0 .0 1.0 x2.mn1@vth0@ILN .0 .0 .0 .0 1.0 -1.0 Option Sampling_Method=External Block_Name=test1 .End_Variation The data block syntax is the same as for the regular HSPICE data block from .Data to .Enddata. The first variable is always the index. All identifiers for the variables start with “I” because this is the only variable type which can be set externally. The feature itself is invoked by specifying the external sampling method, with the appropriate block name. To run a particular sample from the data block use the following MCcommand: monte = list(num) or monte = list(<num1:num2> <num3> <num4:num5>) If the netlist or the model or both are encrypted, the hash codes printed in the parameter file are recognized by HSPICE when reading in the data block. Additional rules: 1. HSPICE does not check the range of the values in the supplied data block against option value Normal_Limit. 2. Independent random variables which are not specified in the data block are set to zero (no variation). Application Considerations If the variations that are applied are too large, generally caused by the combinations of variation specified in the variation block and the value of Normal_Limit, some circuits can show abnormal behavior and produce unrealistic results for certain samples. This can distort the summary statistics reported by HSPICE at the end of the Monte Carlo simulation. Therefore, you HSPICE® User Guide: Simulation and Analysis B-2008.09 555 Chapter 21: Monte Carlo Analysis Using the Variation Block Flow Known Limitations should review the individual measurement results for outliers and analyze them properly. For example, when plotting measurement results as a function of index in CosmosScope, the outliers are readily apparent. Known Limitations One Dimensional Monte Carlo Simulation Running a Monte Carlo simulation with variation block does not support a one dimensional sweep such as .DC sweep MONTE=50. The run fails to converge and HSPICE issues an error message. Use the following workaround: Insert a dummy one point sweep, for example: .param dummy = 1 .dc dummy 1 1 1 monte=50 .measure dc v1 find v(node1) at = 1 The Monte Carlo analysis runs properly and reports all the data points. Troubleshooting Monte Carlo Issues Independent Random Variable Assignments If you add additional independent random variables to a Monte Carlo run you might see that none of these variables have any impact on the simulation run. But you might see differences in statistical results between simulations with and without these additional independent random variables. This may raise skepticism, as there is no difference in the results if you run the case more than once with the same set of independent random variables. The difference is not due to varying the number independent random variables but because of the way random values are assigned to them. Consider the following two cases two cases where the only difference is the number of independent random variables. 556 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 21: Monte Carlo Analysis Using the Variation Block Flow Troubleshooting Monte Carlo Issues Let two random variables be defined in case 1: .variation .spatial_variation Parameter a = N( ) Parameter b = N( ) Parameter Slope = 'a/50u' Parameter Pi = 3.14159265 Parameter Angle = 'Pi*2*b' R rmodel rsh=Perturb('Slope*sqrt(Get_E(x)* Get_E(x)+ Get_E(y)* Get_E(y)) \\ *cos(Angle-atan(get_e(y)/get_e(x))-(get_E(x)<0?Pi:0))') .end_spatial_variation .end_variation Random variables a and b are used to calculate variations in sheet resistivity as a function of a resistor's coordinates. Let case 2 have four random variables defined: .variation .spatial_variation Parameter a = N( ) Parameter b = N( ) Parameter c = N( ) Parameter d = N( ) Parameter Slope = 'a/50u' Parameter Pi = 3.14159265 Parameter Angle = 'Pi*2*b' R rmodel rsh=Perturb('Slope*sqrt(Get_E(x)* Get_E(x)+ Get_E(y)* Get_E(y))\\ *cos(Angle-atan(get_e(y)/get_e(x))-(get_E(x)<0?Pi:0))') .end_spatial_variation .end_variation Random variables a and ' are used in the Variation Block; c and d are not used. During the Monte Carlo sweep, a pseudo random number generator creates an array of random values (Random1, Random2,...,RandomN) and assigns them to each an independent random variable. In case 1, the random number assignment is: Monte=1 -- a=Random1 b=Random2 Monte=2 -- a=Random3 b=Random4 ... Monte=N -- a=Random2N-1 b=Random2N In case 2, the random number assignment is: HSPICE® User Guide: Simulation and Analysis B-2008.09 557 Chapter 21: Monte Carlo Analysis Using the Variation Block Flow Troubleshooting Monte Carlo Issues Monte=1 -- a=Random1 b=Random2 c=Random3 d=Random4 Monte=2 -- a=Random5 b=Random6 c=Random7 d=Random8 ... Monte=N -- a=Random4N-3 b= Random4N-2 c=Random4N-1 d=Random4N Here, although Random1 through RandomN are the same in both cases, the sequence of assignment to independent random variables differs. Hence, the individual samples of a (or b) differ between the two simulations. As a consequence, at low sample numbers the difference in the standard deviation (sigma) of the distributions of a (or b) might be quite large. For higher sample numbers, the differences get smaller, according to the general convergence rate of Monte Carlo results of 1n where n is the number of samples. Because a pseudo random number generator is used in HSPICE, repeated simulations generate the same set of statistical results for a given set of independent random variables. The user can change the random number sequences at each run by defining in the Variation Block: Option Stream = val ≤ , val ≤ In the obsolete traditional Monte Carlo style, this is the equivalent of setting: .option seed=val When using Monte Carlo simulation, you should keep in mind that there is always uncertainty associated with this method in the relationship of one sample to the overall population. 558 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 21: Monte Carlo Analysis Using the Variation Block Flow References References [1] V. Czitrom: One-Factor-at-a-Time Versus Designed Experiments. The American Statistician, pp.126-131, May 1999. [2] M.D. McKay, R.J. Beckman, and W.J. Conover: A Comparison of Three Methods for Selecting Values of Input Variables in the Analysis of Output from a Computer Code. Technometrics, pp. 239-245, 1979. [3] M. Stein: Large Sample Properties of Simulations Using Latin Hypercube Sampling. Technometrics, pp. 143-151, 1987. HSPICE® User Guide: Simulation and Analysis B-2008.09 559 Chapter 21: Monte Carlo Analysis Using the Variation Block Flow References 560 HSPICE® User Guide: Simulation and Analysis B-2008.09 22 Mismatch Analyses 22 Describes the use of DC and AC mismatch analyses in HSPICE. DCMatch and ACMatch analyses are efficient techniques for computing the effects of variations on a circuit's DC or AC response. The variation definitions are taken from the Variation Block. Both methods are small signal analyses, similar to noise analysis. Unlike the traditional Monte Carlo analysis, these new methods do not rely on sampling, and are therefore significantly faster. The Monte Carlo results converge to those from DCMatch or ACMatch analysis for a large number of samples, provided that the circuit characteristics are close to linear in Monte Carlo analysis (for example no clipping or hysteresis). DCMatch and ACMatch analyses are affected by the control options specified in the Variation Block, see Control Options and Syntax in the chapter Analyzing Variability and Using the Variation Block. These topics are covered in the following sections: ■ Mismatch ■ DCMatch Analysis ■ ACMatch Analysis ■ Application Considerations ■ Mismatch Compared to Monte Carlo Analysis Mismatch Variations in materials and processing steps are the source of differences in the characteristics of identically designed devices in close proximity on the same integrated circuit. These are random time-independent variations by nature and are collectively called mismatch. HSPICE® User Guide: Simulation and Analysis B-2008.09 561 Chapter 22: Mismatch Analyses DCMatch Analysis Mismatch is one of the key limiting factors in analog signal processing. It affects more and more circuit types as device dimensions and signal swings are reduced. Mismatch is a function of the geometry of the devices involved, their spatial relationship (distance and orientation) and their environment. This chapter discusses the following mismatch analyses: ■ DCMatch Analysis ■ ACMatch Analysis DCMatch Analysis When the effects of variation on DC response of a circuit are of interest, a method called DC mismatch (DCMatch) analysis can be used. In DCMatch analysis, the combined effects of variations of all devices on a specified node voltage or branch current are determined. The primary purpose is to consider the effects of Local variations (that is, for devices in close proximity). DCMatch analysis also allows for identifying groups of matched devices (that is, devices that should be implemented on the layout according to special rules). A secondary set of results is calculated from the influences of Global and Spatial Variations, which is useful for investigating whether their effects on circuit response are much smaller than the effects of Local variations, when optimizing a design. DCMatch analysis is based on the following dependencies and assumptions: ■ variations in device characteristics are modeled through variations in the underlying model parameters. ■ effects on a circuit’s DC solution are small and can be modeled as a linear combination of the variations in the random variables. In HSPICE, the variations in model parameters are defined in the Variation Block (see Chapter 20, Analyzing Variability and Using the Variation Block). Those definitions are used to calculate the variation in DC response. DCMatch analysis runs either from a default operating point or for each value of the independent variable in a DC sweep. The default output is in the form of tables containing the sorted contributions of the relevant devices to the total variation, as well as information on matched devices. In the current implementation, a heuristic algorithm makes a best guess effort to identify matched devices. This means that the results are suggestions only. In addition to the table, the total variation and contributions of selected devices can be output using .PROBE and .MEASURE commands. 562 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 22: Mismatch Analyses DCMatch Analysis Input Syntax .DCMatch OUTVAR [THRESHOLD=T] [FILE=string] [INTERVAL=Int] Parameter Description OUTVAR One or more node voltages, voltage differences for a node pair, or currents through an independent voltage source. THRESHOLD Report devices with a relative variance contribution above Threshold in the summary table. ■ T=0: reports results for all devices T<0: suppresses table output; however, individual results are still available through .PROBE or .MEASURE statements. The upper limit for T is 1, but at least 10 devices are reported, or all if there are less than 10. Default value is 0.01. ■ FILE Valid file name for the output tables. Default is basename.dm# where “#” is the usual sequence number for HSPICE output files. INTERVAL Applies only if a DC sweep is specified. Int is a positive integer. A summary is printed at the first sweep point, then for each subsequent increment of Int, and then, if not already printed, at the final sweep point. Note: If more than one DCMatch analysis is specified per simulation, only the last statement is used. Example 1 In this example, HSPICE reports DCMatch variations on the voltage of node 9, the voltage difference between nodes 4 and 2, and on the current through the source VCC. .DCMatch V(9) V(4,2) I(VCC) Example 2 In this example, the variable XVal is being swept in the DC command from 1k to 9k in increments of 1k. DCMatch variations are calculated for the voltage on node out. Tables with DCMatch results are generated for the set XVal={1K, 4K, 7K, 9K}. .DC XVal Start=1K Stop=9K Step=1K .DCMatch V(out) Interval=3 HSPICE® User Guide: Simulation and Analysis B-2008.09 563 Chapter 22: Mismatch Analyses DCMatch Analysis DCMatch Table Output For each output variable and sweep point, HSPICE generates a result record that includes setup information, total variations, and a table with the sorted contributions of the relevant devices. The individual entries are: ■ Sweep or operating points for which the table is generated ■ Name of the output variable ■ DC value of this output variable ■ Values used for DCMatch options ■ Output sigma due to combined Global, Local, and Spatial variations σ 2 global +σ local 2 +σ 2 spatial ■ Results for Global variations which are similar to the specifics of Local Variation ■ Results for Local variations: • Number of devices that had no local variability specified • Output sigma due to Local variations • Number of devices with local variance contributions below the threshold value and not included in the table • Table with sorted device contributions Contribution sigma (in volts or amperes). Values below 100nV or 1pA are rounded to zero to avoid reporting numerical noise. • Contribution variance for ith parameter (in percent) 2 σ (i) ---------------- × 100 n 2 ∑σ( k ) 1 The parameter “Threshold” applies to this column. • 564 Cumulative variance through ith parameter (in percent) HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 22: Mismatch Analyses DCMatch Analysis i ∑ σ( k ) 2 1 ------------------- × 100 n ∑ σ( k ) 2 1 The table also includes a suggestion on matched devices that should be verified independently. Devices with the same number in the column “Matched pair” are likely to be matched. Their layout should be reviewed for conformity to established matching rules. ■ Results for Spatial variations are similar to the previous item, Local Variation. Example sweep point = operating point =============================================================== output = v(out) node voltage = 1.25V threshold = 1.000E-02 perturbation = 2.00 interval = 1 Output 1-sigma due to total variations = 548.32uV DCMatch GLOBAL VARIATION 10 Devices had no Global Variability specified. Output 1-sigma due to Global variations = 29.11uV -------------------------------------------------------------Contribution Contribution Cumulative Independent 1-Sigma(V) Variance (%) Variance (%) Variable 20.11u 47.75 47.75 snps20p@vth0 18.90u 42.18 89.94 snps20p@u0 8.97u 9.49 99.43 snps20n@u0 2.20u 571.20m 100.00 snps20n@vth0 DCMatch LOCAL VARIATION 10 Devices had no Local Variability specified Output 1-sigma due to Local variations = 547.74uV 4 Devices with Contribution Variance larger than Threshold --------------------------------------------------------------Contribution Contribution Cumulative Matched Device 1-Sigma(V) Variance (%) Variance (%) pair Name 295.72u 29.17 29.17 1 xi82.mn1 295.49u 29.12 58.29 1 xi82.mn2 251.96u 21.17 79.47 2 xi82.mp4 247.81u 20.48 99.95 2 xi82.mp3 10.02u 33.52m 99.98 0 r1 6.48u 14.02m 100.00 0 xi82.mp5 3.15u 3.31m 100.00 0 xi82.mp5 1.72u 984.01u 100.00 0 xi82.r0 657.79n 144.32u 100.00 0 xi82.mn6 0. 0. 100.00 0 xi82.mn8 HSPICE® User Guide: Simulation and Analysis B-2008.09 565 Chapter 22: Mismatch Analyses DCMatch Analysis Output Using .PROBE and .MEASURE Commands Depending on the output variable specified on the .DCMatch command, results produced by DCMatch analysis can be saved by using .PROBE and .MEASURE commands (see syntax and examples that follow). If multiple output variables are specified, a result is produced for the last variable only. A DC sweep needs to be specified to produce these kinds of outputs; a single point sweep is sufficient. The keywords available for saving specific results from DCMatch analysis are: Table 64 Keyword descriptions from DCMatch Analysis Keyword Description DCM_Total Output sigma due to Global and Local variations. DCM_Global Output sigma due to Global variations. DCM_Global(par) Contribution of parameter “par” to output sigma due to Global variations. Here, 'par' can be an independent variable or a model parameter. DCM_Local Output sigma due to Local variations. DCM_Local(dev) Contribution of device “dev” to output sigma due to Local variations. DCM_Spatial Output sigma due to Spatial Variations. DCM_Spatial(var) Contribution of independent variable “var” to output sigma due to Spatial Variations. Syntax for .PROBE Command for DCMatch A .PROBE statement in conjunction with .OPTION POST creates a data file with waveforms that can be displayed in CosmosScope. 566 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 22: Mismatch Analyses DCMatch Analysis .PROBE .PROBE .PROBE .PROBE .PROBE .PROBE .PROBE .PROBE DC DC DC DC DC DC DC DC DCM_Total DCM_Global DCM_Local DCM_Global(VariableName) DCM_Global(ModelType,ModelName,ParameterName) DCM_Local(InstanceName) DCM_Spatial DCM_Spatial(VariableName) This type of output is useful for plotting the effects of mismatch as a function of bias current, temperature, or a circuit parameter. Examples In the first example, the contribution of the variations on vth0 (threshold) of the nmos devices with model SNPS20N is saved. In the second example, the contribution of device mn1 in subcircuit X8 is saved. .Probe DCM_Global(nmos,SNPS20N,vth0) .Probe DCM_Local(X8.mn1) Syntax for .MEASURE Command With .MEASURE statements, HSPICE performs measurements on the simulation results and saves them in a file with a .ms# extension. .MEAS .MEAS .MEAS .MEAS .MEAS .MEAS .MEAS .MEAS .MEAS .MEAS DC DC DC DC DC DC DC DC DC DC res1 max DCM_Total res2 max DCM_Global res3 max DCM_Local res4 max DCM_Global(VariableName) res5 max DCM_Global(ModelType,ModelName,ParameterName) res6 max DCM_Local(InstanceName) res7 find DCM_Local at=SweepValue res8 find DCM_Local(InstanceName) at=SweepValue res9 max DCM_Spatial res10 find DCM_Spatial(VariableName) at=SweepValue Example In this example, the result systoffset reports the systematic offset of the amplifier; the result matchoffset reports the variation due to local mismatch; and the result maxoffset reports the maximum (3-sigma) offset of the amplifier. .MEAS DC systoffset avg V(inp,inn) .MEAS DC matchoffset avg DCM_Local .MEAS DC maxoffset param='abs(systoffset)+3.0*matchoffset' HSPICE® User Guide: Simulation and Analysis B-2008.09 567 Chapter 22: Mismatch Analyses DCMatch Analysis DCMatch Example Netlist An example netlist for running DCMatch analysis using a classic 7-transistor CMOS operational amplifier is available in the HSPICE demo directory as \$<installdir>/demo/hspice/variability/opampdcm.sp In this netlist, device sizes are set up as a function of a parameter k, which allows for investigating the effects of the Global and Local Variations as a function of device size. The following lines relate to DCMatch analysis: ... .param k=2 ... mn1 net031 inn net044 nmosbulk snps20N L='k*0.5u' W='k*3.5u' M=4 mn2 net18 inp net044 nmosbulk snps20N L='k*0.5u' W='k*3.5u' M=4 mp3 net031 net031 vdda pmosbulk snps20P L='k*0.5u' W='k*4.5u' M=4 mp4 net18 net031 vdda pmosbulk snps20P L='k*0.5u' W='k*4.5u' M=4 ... .Variation .Global_Variation Nmos snps20N vth0=0.07 u0=10 % Pmos snps20P vth0=0.08 u0=8 % .End_Global_Variation .Local_Variation Nmos snps20N vth0='1.234e-9/ sqrt(get_E(W)*get_E(L)*get_E(M))' + u0='2.345e-6/sqrt(get_E(W)*get_E(L)*get_E(M))' % Pmos snps20P vth0='1.234e-9/ sqrt(get_E(W)*get_E(L)*get_E(M))' + u0='2.345e-6/sqrt(get_E(W)*get_E(L)*get_E(M))' % .Element_Variation R r=10 % .End_Element_Variation .End_Local_Variation .End_Variation ... .DCMatch v(out) .dc k start=1 stop=4 step=0.5 ... .meas DC systoffset find V(in_pos,in_neg) at=2 .meas DC dcmoffset find DCM_Local at=2 .meas DC maxoffset param='abs(systoffset)+3.0*dcmoffset' .meas DC dcm_mn2 find DCM_Local(xi82.mn2) at=2 .meas DC gloffset find DCM_Global at=2 .option post ... The DCMatch analysis produces four types of output from this netlist: 568 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 22: Mismatch Analyses ACMatch Analysis ■ table from operating point with k=2 in the output listing ■ table from DC sweep for k=1 to 4 in file opampdcm.dm0 ■ waveform for output variation as a function of k in file opampdcm.sw0 ■ in file opampdcm.sw0 for k=2: • values for systematic offset • output sigma due to Local Variation • 3-sigma amplifier offset • contribution of device mn2 to output sigma due to Local Variation • output sigma due to Global Variation ACMatch Analysis In ACMatch analysis, the combined effects of variations of device characteristics on the frequency response of a circuit are determined. The variation definitions are taken from the Variation Block. The main application for ACMatch analysis is in the simulation of circuits which are sensitive to parasitics or require matching of parasitics, for characteristics such as delays and power supply rejection. ACMatch analysis takes the changes in frequency response due to variations in DC parameters (which affect operating point and low frequency response, as well as bias dependent capacitors) and due to variations in AC parameters. Note that variation on the stimuli (voltage and current sources) can be specified on the DC and AC parameters, and both types are considered in the ACMatch analysis. ACMatch analysis is similar to DCMatch analysis in that: ■ It is efficient compared to Monte Carlo analysis because there is no sampling involved. ■ Variations in component characteristics are modeled through variations in the underlying model parameters. ■ Effects on a circuit's DC solution are small, and can be modeled as a linear combination of the variation in independent random variables. This is relevant for ACMatch analysis because the changes in the DC solution affect the circuit's AC characteristics. HSPICE® User Guide: Simulation and Analysis B-2008.09 569 Chapter 22: Mismatch Analyses ACMatch Analysis ACMatch analysis is specified with an AC analysis, which defines the frequencies for which the circuit is analyzed; this can be a single or multiple sweep points. At least one measure or other output statement is required for this AC analysis, and subsequently ACMatch analysis, to run. The primary output of ACMatch analysis is a table with the sorted parameter and device contributions. Input Syntax .ACMatch OUTVAR <THRESHOLD=T> <FILE=string> <INTERVAL=Int> Parameter Description OUTVAR OutputVariable can be one or several output voltages, difference voltages or branch current through an independent voltage source. The voltage or current specifier is followed by an identifier of the AC quantity of interest: M P phase R real part I THRESHOLD magnitude imaginary part Report devices with a relative variance contribution above Threshold in the summary table. ■ T=0: reports results for all devices T<0: suppresses table output; however, individual results are still available through .PROBE or .MEASURE statements. The upper limit for T is 1, but at least 10 devices are reported, or all if there are less than 10. Default value is 0.01. ■ FILE Valid file name for the output tables. Default is basename.am# where “#” is the usual sequence number for HSPICE output files. INTERVAL Relates to the associated AC sweep. Int is a positive integer. A summary is printed at the first sweep point, then for each subsequent increment of Int, and then, if not already printed, at the final sweep point. If more than one ACMatch analysis is specified per simulation, only the last statement is executed. 570 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 22: Mismatch Analyses ACMatch Analysis Example .ACMatch VM(out) VP(out) .AC dec 10 1k 10Meg interval=10 ACMatch Table Output For each output variable and sweep point, HSPICE generates a result record in a file with default extension .am#, which includes setup information, a main result with the total variations, and a table with the sorted contributions of the relevant devices and parameters. The individual entries include: ■ frequency sweep value ■ name of the output variable ■ AC magnitude of this output variable ■ ACMatch option values ■ number of devices which had no variability specified ■ output sigma values due to combined Global and Local Variations ■ result for Global Variations ■ contributions of parameters to Global Variations ■ results for Local Variations ■ contributions of devices to Local Variations The entries in the different columns correspond to those described in the section on DCMatch Table Output. To avoid printing unreliable results due to precision issues, phase output is not available in the table if the associated magnitude of the same variation type is less than 1uV for voltage or 1nA for current output. A warning is printed instead. HSPICE® User Guide: Simulation and Analysis B-2008.09 571 Chapter 22: Mismatch Analyses ACMatch Analysis Example frequency = 1.00000D+06 =============================================================== ======= output = v(out) node voltage = 1.87 V threshold = 1.000E-02 perturbation = 2.00 interval = 1 Output 1-sigma due to Global and local Variations = 48.68mV ACMatch GLOBAL VARIATION 10 Devices had no Global Variability specified Output 1-sigma due to Global Variations = 46.97mV --------------------------------------------------------------------Contribution Contribution Cumulative Independent 1Sigma(V) Variance (%) Variance (%) Variable 38.89m 68.57 68.57 snps20n@vth0 15.78m 11.28 79.85 snps20p@vth0 15.08m 10.31 90.16 snps20n@tox 14.56m 9.61 99.77 snps20n@u0 1.80m 146.80m 99.91 snps20p@u0 1.38m 86.49m 100.00 snps20p@tox ACMatch LOCAL VARIATION 6 Devices had no Local Variability specified Output 1-sigma due to Local Variations = 12.79mV 7 Devices with Local Contribution Variance larger than Threshold -------------------------------------------------------------------Contribution Contribution Cumulative Device 1Sigma(V) Variance (%) Variance (%) Name 7.43m 33.77 33.77 xi82.mn7 6.26m 23.97 57.73 xi82.mp4 6.20m 23.53 81.26 xi82.mp3 4.87m 14.49 95.75 xi82.mn8 1.53m 1.43 97.18 xi82.mn2 1.49m 1.36 98.54 xi82.mn1 1.40m 1.20 99.74 r1 563.27u 193.90m 99.93 xi82.mp5 239.10u 34.94m 99.97 xi82.rcomp 184.24u 20.75m 99.99 xi82.mn6 Output from .PROBE and .MEASURE Commands for ACMatch The syntax of .MEASURE and .PROBE commands for ACMatch analysis is similar to the syntax for DCMatch analysis: 572 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 22: Mismatch Analyses ACMatch Analysis Syntax for .PROBE Command A .PROBE statement in conjunction with .OPTION POST creates a data file with waveforms that can be displayed in CosmosScope. .PROBE .PROBE .PROBE .PROBE .PROBE .PROBE AC AC AC AC AC AC ACM_Total ACM_Global ACM_Local ACM_Global(VariableName) ACM_Global(ModelType,ModelName,ParameterName) ACM_Local(InstanceName) Syntax for .MEASURE Command With .MEASURE statements, HSPICE performs measurements on the simulation results and saves them in a file with a .ma# extension. .MEAS .MEAS .MEAS .MEAS .MEAS .MEAS .MEAS .MEAS AC AC AC AC AC AC AC AC res1 res2 res3 res5 res6 res7 res8 res9 max ACM_Total max ACM_Global max ACM_Local max ACM_Global(VariableName) max ACM_Global(ModelType,ModelName,ParameterName) max ACM_Local(InstanceName) find ACM_Local at=SweepValue find ACM_Local(InstanceName) at=SweepValue Example An example netlist for running ACMatch analysis using a classic 7-transistor CMOS operational amplifier is available in the HSPICE demo directory as \$<installdir>/demo/hspice/variability/opampacm.sp. The following lines relate to ACMatch analysis: HSPICE® User Guide: Simulation and Analysis B-2008.09 573 Chapter 22: Mismatch Analyses ACMatch Analysis .Variation .Global_Variation Nmos snps20N vth0=0.07 u0=10 % tox=3 % Pmos snps20P vth0=0.08 u0=8 % tox=3 % .End_Global_Variation .Local_Variation Nmos snps20N vth0='1.234e-9 sqrt(get_E(W)*get_E(L)*get_E(M))' + u0='2.345e-6/sqrt(get_E(W)*get_E(L)*get_E(M))' % + tox='3.456e-6/sqrt(get_E(W)*get_E(L)*get_E(M))' % Pmos snps20P vth0='1.234e-9/ sqrt(get_E(W)*get_E(L)*get_E(M))' + u0='2.345e-6/sqrt(get_E(W)*get_E(L)*get_E(M))' % + tox='3.456e-6/sqrt(get_E(W)*get_E(L)*get_E(M))' % .Element_Variation R r=10 % .End_Element_Variation .End_Local_Variation .End_Variation .ACMatch v(out) .ac dec 1 1k 10Meg .meas ac res1 find acm_local at=1k In this example, ACMatch analysis runs at 1kHz, 10kHz, 100kHz, 1MHz, and 10MHz. After simulation, the results in opampacm.am0 show the contributions of devices and parameters, and their different relative importance for the different frequencies. In addition, the measurement result is printed in opampacm.ma0. Application Considerations ACMatch analysis results match those of a small signal Monte Carlo Analysis. Discrepancies arise with certain test setups, if the operating point in Monte Carlo analysis varies by a large amount. For example, the output of an amplifier might saturate at one of the supply rails for some samples, if it is configured for high gain at DC. If such conditions exist, and the amplifier is used with the same gain configuration in the real application, then they point to issues which need to be investigated with DCMatch analysis and resolved first. Otherwise, the DC gain configuration of the amplifier needs to be changed in the test setup. 574 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 22: Mismatch Analyses ACMatch Analysis Mismatch Compared to Monte Carlo Analysis DCMatch and ACMatch analyses use calculus of probability instead of sampling. The following table shows a comparison of the two types. Feature Mismatch Monte Carlo Analysis type DC or AC AC, DC, Transient Device/parameter contribution report Yes No Relative run time Fast Slow Accuracy Good Dependent on number of samples Distributions Normal preferred Any Variation result report Global, Local, Spatial and Interconnect separate Global, Local, Spatial and Interconnect combined HSPICE® User Guide: Simulation and Analysis B-2008.09 575 Chapter 22: Mismatch Analyses References References [1] M.Pelgrom, A.Duinmaijer, and A.Welbers: “Matching Properties of MOS Transistors”, IEEE J. Solid-State Circuits, pp. 1433-1439, May 1989. [2] P.R.Kinget: “Device Mismatch and Tradeoffs in the Design of Analog Circuits”, IEEE J. Solid-State Circuits, pp. 1212-1224, June 2005. 576 HSPICE® User Guide: Simulation and Analysis B-2008.09 23 23 Exploration Block Describes the use of the Exploration Block in HSPICE. The Exploration Block addresses the designer’s need to study the behavior and sensitivities of circuits to come up with an optimum design. During this early design phase, the designer may want to explore ranges of device sizes for a given circuit topology. The Exploration Block feature allows the designer to describe a set of experiments with different geometries, without changes to the original netlist. The Exploration Block is closely related to the Variation Block with external sampling (see Chapter 20, Analyzing Variability and Using the Variation Block). These topics are covered in the following sections: ■ Exploration Block Description ■ Usage Model ■ Flow Using an External Exploration Tool ■ Exploration Block Syntax ■ Export File Syntax ■ Executing Exploration in HSPICE ■ Exploration Data Block Syntax ■ Exploration Block Interactions Exploration Block Description The Exploration Block extracts the parameters suitable for exploration from a netlist, and thus eliminates parsing by the Exploration tool. The parameters are presented in a normalized format. This solution eliminates the exploration tool’s HSPICE® User Guide: Simulation and Analysis B-2008.09 577 Chapter 23: Exploration Block Usage Model need to rewrite the netlist with new parameter values. Using the Exploration Block, the Exploration tool returns only the updated values of the parameters which need to be changed in the course of a set of exploration simulations. HSPICE finds all the places where they need to be applied. The Exploration Block contains a section with options, and may include a data block with instructions on how to change certain parameters on individual devices or device groups. The data block must be created outside the simulator, based on information from the simulator and considerations specific to the particular design, possibly from an optimization program. Usage Model To accommodate time restriction, exploration needs to be applied in an organized manner, with the smallest number of unrelated variables. A strategy which has proven useful is to take into account that integrated circuits are built with hierarchy, and that there are known relationships between devices for best results (partial and full matching). In essence, the designer's knowledge about the circuit is encapsulated in the way exploration is carried out. Experience with optimization tools has shown that this information is crucial for success, but also difficult to set up correctly. Multiple Instantiations of the Same Cell or Subcircuit In a typical design process, a large circuit is assembled from cells out of existing libraries. Each cell has different descriptions, for different applications: subcircuit, layout, behavioral model, etc. The circuit netlist describes how the cells are connected with other cells, and contains a description of their content. Exploration of HSPICE is restricted to the hierarchical mode only with this release. In hierarchical mode, exploration is cell-oriented, meaning that all instantiations of a particular cell are affected the same way. With this usage model, if designers wish to explore separate instantiations of the same cell in a different manner, then they need to create new cell names, with their content definitions repeated, before exploration can start. This renaming procedure needs to be done anyhow for the final design, if the designer accepts new device sizes coming out of the exploration exercise because a basic rule of a circuit description is that multiple cell definitions with same name (and possibly different content) are not allowed. 578 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 23: Exploration Block Usage Model Specifying Relationships between Devices The following relationships between different devices can be specified in the Exploration Block to force matching: device1Property1=expression of device2Property1 Such expressions reduce the number of variables for exploration because derived properties are processed inside of HSPICE. These relationship rules will be applied to all the devices subject to exploration. Therefore even if no change is requested from the Exploration tool, HSPICE executes these rules. So, if for example the lengths of devices opamp.mn1 and opamp.mn2 are different in the netlist, they will be the same in a simulation which contains an Exploration block with the rule that they should be the same. A simplified syntax expresses relationships of a whole set of device properties. Examples: length(opamp.mn1)=length(opamp.mn2) opamp.mp4=opamp.mp3 mp4 will be identical to mp3, in all properties bias.mn5=2*bias.mn6 mn5 consists of 2 devices in parallel, which are identical to mn6 Specifying Relationships between Properties To cover appropriate scaling of secondary properties on the same device, the following relationships can be specified: deviceProperty2=expression of deviceProperty1. Example: ad='120n*W' as='120n*W' ps='240n+W' pd='240n+W' HSPICE® User Guide: Simulation and Analysis B-2008.09 579 Chapter 23: Exploration Block Usage Model Subcircuits and Elements Supported for Exploration The exploration feature is primarily designed for design work on integrated circuits in CMOS technology. In a first implementation, Exploration is supported for ■ Independent sources: DC value ■ MOS devices: W, L, M, dtemp ■ Resistors: R or W, L, M, dtemp ■ Capacitors: C or W, L, M, dtemp When designing circuits, the multiplicity factor M is always a positive integer, but the Exploration tool can request arbitrary positive values. To preserve relationships which have been previously defined through expressions, exploration can only be applied to parameters which are defined with numerical values. Example1 m1 out in1 vdd vdd pch w=wp l=100n m=3 Exploration can be applied to element parameters l and m, but not to w directly. Example 2 subckt nand m1 out m2 out m3 out m4 mid .ends nand in1 in1 in2 in1 in2 in2 out wp=100n wn=50n len=100n vdd vdd pch w=wp l=len vdd vdd pch w=wp l=len mid gnd nch w=wn l=len gnd gnd nch w=wn l=len Exploration can be applied to subcircuit parameters wp, wn and len. The application envisioned here is for leaf cells with programmable layout: separate width and common length of pmos and nmos devices. 580 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 23: Exploration Block Flow Using an External Exploration Tool Example 3 .subckt onebit in1 in2 carry-in out carry-out x1 in1 in2 7 nand x2 in1 7 8 nand wp=100n wn=100n x3 in2 7 9 nand wp=300n wn=150n .ends onebit subckt nand in1 in2 out wp=200n wn=100n m1 out in1 vdd vdd pch w=wp l=100n m2 out in2 vdd vdd pch w=wp l=100n m3 out in1 mid gnd nch w=wn l=100n m4 mid in2 gnd gnd nch w=wn l=100n .ends nand The subcircuit named onebit can be used for exploration because it instantiates other subcircuits using parameters with numerical values: wn and wp of nand gates x2 and x3. The subcircuit called nand can be used for exploration on the default values wn and wp (exploration only affects instantiation x1 because x2 and x3 parameters override the default values). The devices m1 to m4 can be used for exploration on their length but not on the width. This preserves the imposed relationship of equal width for m1 and m2, and for m3 and m4. Exploration supports variation in temperature, in addition to element and subcircuit parameters. Encrypted sections of a netlist are not available for exploration. Flow Using an External Exploration Tool The design flow consists of an information extraction and export phase in HSPICE, a Definition phase for the Exploration Block outside of HSPICE, and an Exploration phase in HSPICE. Export Phase HSPICE creates an output file with the Export Block. It contains in the first section the names of the variables suitable for exploration, parameters, element and subcircuit parameters, along with appropriate identifiers, which include subcircuit name, device instance names, models and properties. In the second section, the corresponding values are listed. HSPICE® User Guide: Simulation and Analysis B-2008.09 581 Chapter 23: Exploration Block Flow Using an External Exploration Tool From Example 3 on page 581: ■ Subcircuit onebit with properties wn and wp for instantiations x2 and x3 ■ Subcircuit nand with properties wp and wn (only useful if an instantiation exists where wp and wn are not defined, as in onebit.x1) ■ m1 to m4 with properties l In the export phase, HSPICE runs a simulation from the originally supplied netlist, ignoring any Exploration Block content other than options. Definition Phase Note: You must create or adapt the external utility described in the following sections; it is not provided by HSPICE. ■ An external utility reads the files created by HSPICE with the device information. ■ Supplemental information to the external utility consists of technology and details of the experiment. ■ The utility creates a set of experiments and formulates them as a data block, with some or all variables contained in the Export Block, and one or more sets of exploration data. ■ The utility submits the netlist with Exploration Block to HSPICE. Exploration Phase ■ HSPICE applies the content of the data block, calculates the secondary parameters, and runs a set of simulations with the updated device geometries as specified in the Exploration Block. HSPICE produces measurement results and a file with all the parameter values used for each exploration simulation. ■ The external utility analyzes and combines the simulation results. ■ Based on the results, the utility might specify another set of experiments, with a new set of simulations, and run through these steps until some predefined goal is reached. Refer to the Figure 99 on page 583, and notice the flow difference before and after adding exploration block. 582 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 23: Exploration Block Flow Using an External Exploration Tool Tech Info Netlist HSPICE Parameter List Export Explore Matlab, External Perl script, Exploration public domain tool Tool Setup Results Modified Parameter List (variables) HSPICE Figure 99 Exploration Block Flow Netlist Export At the end of the exploration procedure, a valid netlist needs to be generated which reflects the final choices for the device sizes, in order to be able to drive a layout tool and run a successful LVS (layout versus schematic verification). HSPICE® User Guide: Simulation and Analysis B-2008.09 583 Chapter 23: Exploration Block Exploration Block Syntax Exploration Block Syntax Because the Exploration Block is closely related to the Variation Block, the internal structure is similar, in particular when compared with external sampling. Major differences include: ■ The Variation Block specifies variation on the final device size, whereas the Exploration Block deals with the values as defined in the netlist. ■ Perturbations specified in the Variation Block are applied in a flat manner, whereas those from Exploration Block apply to subcircuits, or cells. In the following sections, a period is used as separator between a subcircuit name and an element name. For example: opamp.rbias refers to the resistor rbias instantiated in subcircuit opamp. A period is also used as separator between subcircuit names, if one subcircuit is defined within another. For example: opamp.bias.rbias refers to the resistor rbias in subcircuit bias, nested within subcircuit opamp. Syntax Structure The current implementation of the Exploration Block is structured with options, parameters, relationships between devices, relationships between properties, area calculation, and data block characteristics. .Design_Exploration Options Parameter Parameter_Name = value Parameter Parameter_Name = expression .Data BlockName Index Name … .EndData .End_Design_Exploration Name, … Exploration Block Options The options include: ■ ■ 584 Option Explore only|Do_not_explore Option Export HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 23: Exploration Block Exploration Block Syntax ■ Option Exploration_method ■ Option Ignore_exploration ■ Option Secondary_param If you want to explore only certain cells or subcircuits use: Option Description Option Explore_only Subckts= SubcktList This command is executed hierarchically—the specified subcircuits and all instantiated subcircuits and elements underneath are affected. Thus, if an inverter with name INV1 is placed in a digital control block called DIGITAL and in an analog block ANALOG, and Option Explore_only Subckts = ANALOG, then the perturbations only affect the INV1 in the analog block. You must create a new inverter INV1analog, with the new device sizes. Option Do_not_explore Subckts= Excludes listed subcircuits. SubcktList The two modes of exploration are distinguished by setting either: Option Description Option Export=yes Exports extraction data and runs one simulation with the original netlist Option Export=no (Default) Runs a simulation with Exploration data The perturbation types are selected by setting either: Option Description Option Exploration_method= The Block_name is the same as the name specified in external Block_name= the .DATA block; HSPICE will sweep the row content with Block_name the EXCommand (see the section EXCommand Option: Export Data Block Action). Option Ignore_exploration= (Default=no) HSPICE ignores the content in the yes|no design_exploration block, when Ignore_exploration=yes. HSPICE® User Guide: Simulation and Analysis B-2008.09 585 Chapter 23: Exploration Block Exploration Block Syntax Option Description Option Secondary_param= yes|no (Default = no) If Secondary_param= yes, HSPICE exports the MOSFET secondary instance parameters to a *.mex file (created when option export=yes), and also permits the secondary parameters to be imported as a column header in the .DATA block (option export=no). See the example, following this section. Example: Option secondary_param=yes .design_exploration option secondary_param=yes parameter asad = '1.5e-7' option exploration_method=external block_name=dat2 *nmos snps20n design_area='(get_e(l)+1u)*(get_e(w)+0.8u)' pmos snps20p as = 'asad*get_e(W)' ad ='2*asad*get_E(W)' .data dat2 index vdd@p k@p opamp.rcomp@r@e opamp.r0@r@e r1@r@e r0@r@e opamp.ccomp@c@e c0@c@e c1@c@e opamp.mn1@snps20n@m@e opamp.mn1@snps20n@ad@e opamp.mn2@snps20n@m@e opamp.mn2@snps20n@ad@e opamp.mp3@snps20p@m@e opamp.mp4@snps20p@m@e opamp.mp5@snps20p@l@e opamp.mp5@snps20p@w@e opamp.mp5@snps20p@m@e opamp.mn8@snps20n@l@e opamp.mn8@snps20n@w@e opamp.mn8@snps20n@m@e opamp.mn7@snps20n@l@e opamp.mn7@snps20n@w@e opamp.mn7@snps20n@m@e opamp.mn6@snps20n@l@e opamp.mn6@snps20n@w@e opamp.mn6@snps20n@m@e v2@v@e 1.000 2.5000 2.0000 7.000e+03 1.000e+06 1.000e+06 1.000e+07 9.000e-13 1.000e-03 5.000e-12 4.0000 1.000e-08 4.0000 1.000e-08 4.0000 4.0000 4.000e-07 1.000e-05 3.0000 6.000e-06 3.600e-05 10.0000 6.000e-06 3.600e-05 4.0000 6.000e-06 3.600e-05 6.0000 0. .enddata .end_design_exploration Notice that column header opamp.mn1@snps20n@ad@e can be recognized by HSPICE only if Option Secondary_param=yes. In the netlist for the opamp (not shown above), only the devices mn1 and mn2 have secondary element parameter AD defined. 586 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 23: Exploration Block Exploration Block Syntax The supported MOSFET secondary parameters are: AS, AD, PS, PD, NRD, NRS, RDC, RSC. Parameters Section Parameters can be defined here, which are used in subsequent definitions within the Exploration Block. The name space is separate from the netlist. Parameters specified with numerical values are exported; derived parameters are not exported, thus are not available for exploration. Device Relationships Relationships between element properties exist, which must be respected when changing device size. To reduce the amount of time required by the Exploration Tool to calculate these dependencies, such relationships can be defined directly in the Exploration Block. To force a relationship between two different elements, use the syntax: Element subcircuitName.ElementName parameterName= 'expression of get_E([subcircuitName.]ElementName@parameterName)' The element parameter names here include W and L for NMOS and PMOS devices. The subcircuit name on the right side of the definition is optional, if it is the same as the one on the left side. Element opamp.mn1 l='get_E(mn2@l)' Element inv4.mp1 w='2*get_E(inv2.mp1@w)' These relationships are enforced on all instantiations of subcircuits opamp and inv4 (unless specifically excluded from exploration). Also, properties L of opamp.mn1 and W of inv4.mp1 are not exported, and are not available for exploration. Secondary Element Parameters To calculate secondary element parameters on a single device: Element subcircuitName.ElementName parameterName= 'expression of parameterName' The element parameters here include AD, AS, PD, PS, NRS, and NRD on the left side and expressions of L and W of the same element on the right hand side. For example: HSPICE® User Guide: Simulation and Analysis B-2008.09 587 Chapter 23: Exploration Block Exploration Block Syntax Element opamp.nm1 AD='1e-7*get_E(W)' This relationship is enforced on all instantiations of subcircuit opamp (unless specifically excluded from exploration). Also, the property AD of opamp.mn1 is not exported, and it is not available for exploration. Secondary Device Parameters Expressions for calculating the values of secondary device parameters for all devices with a certain model can be defined. Default values for AD, AS, PD, PS, NRS and NRD are often specific for devices which share the same model, as a function of W and L. ModelType ModelName instanceParameterName='expression of parameterName' For example: nmos snps65n as='asad*get_e(W)' ad='asad*get_e(W)' This directive means that all nmos devices subject to exploration, with model snps65n, and have AS and/or AD specified, have their source and drain areas re-calculated by this equation prior to simulation. If the secondary parameter is not specified on the device, then it is not added. Note that HSPICE simulation results can change when such a definition is added to the Exploration Block, if the original values for AS and AD are different from the values calculated using the expression. While the secondary parameters are not exported, they are available for exploration when defined in the data block (expressions are not supported): Opamp.mn1 AD=1e-12 Same-Circuit Parameters To force relationship between parameters of the same subcircuit, use the syntax Subckt subcircuitName parameterName='expression of parameterName' Note that this function supports only relationship within the same subcircuit. 588 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 23: Exploration Block Exploration Block Syntax Derived Device Properties Derived device properties, as defined in the Exploration Block, are not exported. While specifying device relationship in a direct way is not supported, you can do this through parameter transformations. Example 1: Element opamp.mn1@L = ‘Get_E(opamp.mn2@L)’ Only opamp.mn2@L from the netlist is exported; here, the device property of opamp.mn1@l is not exported. Example 2: nmos nch ad='120n*get_E(W)' + as='120n*get_E(W)' + ps='240n+get_E(W)' + pd='240n+get_E(W)' The properties AD, AS, PS, and PD are not exported. Parameters Defined Outside the Exploration Block The parameters defined outside the Exploration Block can be referenced using the syntax: get_P(parameterName) Area Measurement One of the tradeoffs of integrated circuit design is design area. While an exact number is only available after layout, certain rules can be defined to give a good estimate. The complete measurement consists of three steps: 1. Calculate area of each device, according to model specific expressions 2. Calculate total area of top circuit or specified subcircuit. 3. Make results available to built-in measurement processor for output. The calculation is performed as part of the operating point for AC and TRAN, but executed for each step of a DC transfer characteristics. This allows for reporting area at a certain value of a design parameter, which affects circuit area. However, area is not recalculated if it changes during an AC or transient sweep. HSPICE® User Guide: Simulation and Analysis B-2008.09 589 Chapter 23: Exploration Block Exploration Block Syntax Syntax for device area calculation: Modeltype Modelname design_area = expression Example nmos nch design_area='(get_E(L)+1u)*(get_E(W)+0.8u)' The measurement syntax allows for reporting the area of the whole circuit, or a subcircuit, and has the usual structure: .measure analysisType measName Function design_area(total|subcircuitName) Where, analysisType is DC|AC|Tran, Function can be min, max, find -at. For example: .measure top_area max design_area(total) Rules for Area Measurement The following rules apply for area measurement. 1. Area computation only supports R, C and MOSFET currently. There is no geometry parameter for L, so this element will be ignored in area computation. 2. Typical syntax examples: Compute total circuit area: .measure |dc|ac|tran output_name1 find design_area at=val Hierarchical based, compute the sum area of subcircuit x1: .measure |dc|ac|tran output_name2 find design_area(x1) at=val Compute area of x1.mn1 .measure |dc|ac|tran output_name3 find design_area(x1.mn1) at=val For the equations defining area inside .design_exploration block, only model specific expressions are currently supported: Modeltype Modelname design_area = expression 3. The priority of computing one device area is • 590 For R and C: HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 23: Exploration Block Exploration Block Syntax (i) Expressions defined inside exploration_block (ii) W*L*M (W and L is defined as instance parameter) (iii) Wmodel*Lmodel *M (Wmodel and Lmodel are the model geometry values) (iv) Otherwise, their area is zero. • For MOSFETs: (i) Expressions defined inside exploration_block (ii) W*L*M (W and L are defined as instance parameters) (iii) Wdefault*Ldefault *Mdefault (Wdefault and Ldefault are the default geometry values for MOSFET) (iv) M is the multiplier parameter. 4. If 'scale' is defined, then design_area = area*scale*scale 5. Such measurement works with the .DC |.AC |.TRAN command, whether .design_exploration block is defined or not. Processing Netlist Parameters As shown in the section “Flow Using an External Exploration Tool,” you can have a special case of passing parameter values down one level of hierarchy. In a general case, when HSPICE finds a parameter definition with numerical value (.param paramName=value), it is exported with its name and value in the appropriate section. Parameters which are defined with other parameters instead of numerical values, or expressions of other parameters and numerical values, are not included in the Export file. This preserves relationships between devices, which have been set up by the designer in the original netlist. Example of diffpair in netlist: .subckt diffamp in1 in2 out lpair=2u wpair=2u mpair=4 mn1 d1 in1 s b modelName l=lpair w=wpair m=mpair mn2 d2 in2 s b modelName l=lpair w=wpair m=mpair .... .ends diffamp The subcircuit diffamp with its parameters lpair, wpair and mpair will be in the Export file, with their local values. The devices mn1 and mn2 are not available for exploration. HSPICE® User Guide: Simulation and Analysis B-2008.09 591 Chapter 23: Exploration Block Export File Syntax Export File Syntax HSPICE writes the extracted data from the circuit to a file with the extension “.mex?” with syntax similar to the *.mcx? file, which lists the perturbations created from the Variation Block content. The option settings are reported first, followed by the names of all requested subcircuits and devices with their respective parameter names. Separators are used as follows: ■ A single period is used as hierarchy separator between a subcircuit and an instance or device name, and for separating one or more subcircuit names, if their definitions are nested ■ The @ character is used for separating model and parameter names. ■ Additionally, identifiers are appended as follows to identify the proper owner if an element and a nested subcircuit have the same name: • E for element parameters • P for global parameters, and parameters used in subcircuit definitions and instantiations Syntax Structure The following constructs are provided: ■ For primitives (R,C, without model): [SubcircuitName.]InstanceName@ParamName@E Example: Opamp.rbias@r@E ■ For devices with model (in NMOS, PMOS) [SubcircuitName.]InstanceName@ModelType@ModelName@ParamName@ E Example: Opamp.mn1@snps65n@L@E ■ For standalone parameters: [SubcircuitName@]=ParamName@P 592 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 23: Exploration Block Executing Exploration in HSPICE Example: (.param factor) Opamp@factor@P ■ For parameters declared on subcircuit definition line: [SubcircuitName@]ParamName@P Example: nand@wp@P ■ For parameters appended to subcircuit instantiation: [SubcircuitName.]InstanceName@ParamName@P Example: onebit.x2@wp@P Whenever the optional SubcircuitName is not specified, the top level is assumed (implicit definition). For nested subcircuits, several SubcircuitName entries separated with a period are used. Example Export File onebit.x2@wp@P onebit.x2@wn@P onebit.x3@wp@P onebit.x3@wn@P opamp.mn1@snps65n@L@E opamp.bias.rbias@r@E diffamp@lpair@P diffamp@wpair@P diffamp@mpair@P index1 value1 value2 value3 value4 value5 etc If option export=yes is set, then the output file contains a single data set with the original design values from the netlist. If option export=no (or default) then one data set is written per exploration step, with all the parameters suitable for exploration, not only the ones which were changed through an Exploration Data Block (see Exploration Block Syntax). Executing Exploration in HSPICE Exploration is considered a second sweep, therefore the syntax of the sweep with data block command is used: .DC|.TRAN|.AC analysisDetail sweep EXCommand ...with EXCommand using the keyword explore, otherwise having the same syntax as MCCommand for Monte Carlo. The sample number is optional (and ignored if specified) when data export is requested. The following table shows HSPICE® User Guide: Simulation and Analysis B-2008.09 593 Chapter 23: Exploration Block Exploration Data Block Syntax the tasks performed by the simulator with the different combinations of EXCommand, option Export, and Data Block definition (valid meaning here: defined and having at least one set). Simulation with relationships means that the relationships described in the section Device Relationships are enforced. EXCommand Option: Export Data Block Action EXCommand Option Export Data Block Action Ignored Yes ignored Export and run simulation with original netlist explore No or undefined valid Simulate all sets in Data Block, with relationships explore=5 No or undefined valid Simulate sets 1 to 5 from Data Block, with relationships explore_list=3 No or undefined valid Simulate set 3 from Data Block, with relationships Ignored not defined Simulate with relationships enabled No or undefined Exploration Data Block Syntax The exploration tool output back into HSPICE is a data block, which is referenced in the Exploration Block as “Exploration_Data”. The content is as follows: variableName1 variableName2 variableName3 index1 value11 value12 value13 index2 value21 value22 value23 ...... index is an integer, monotonically increasing. It is sufficient here to include only the cumulative set of parameters which change for the exploration run. Parameter names and values not specified here are left at their original values. 594 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 23: Exploration Block Exploration Block Interactions Exploration Block Interactions The following rules apply per the described circumstances. When an Exploration Block and Variation Block are both present, HSPICE can currently handle sweeps in up to two dimensions. Provided that a Variation Block and an Exploration Block are present, then the following rules apply: ■ There is a monte command only: Exploration Block is ignored ■ There is an explore command only: Variation Block is ignored ■ There is neither monte nor explore command: Variation and Exploration blocks ignored ■ When there is both a monte and explore command and there is/are: • • Several Monte Carlo samples specified, single Exploration request: execute the requested Exploration Data set, with specified Monte Carlo samples. • ■ Single Monte Carlo sample specified: execute Exploration Block content, according to the explore command and option settings. Several Monte Carlo samples and several explore requests: abort, with appropriate message. For multiple Exploration Blocks: • Options are cumulative, the last definition prevails. • Only one named data block can be executed. Limitations The following feature is not implemented in this release. Netlist Export At the end of the exploration procedure, a valid netlist needs to be generated which reflects the final choices for the device sizes, in order to be able to drive a layout tool and run a successful LVS (layout versus schematic verification). HSPICE® User Guide: Simulation and Analysis B-2008.09 595 Chapter 23: Exploration Block Limitations 596 HSPICE® User Guide: Simulation and Analysis B-2008.09 24 24 Optimization Describes optimization in HSPICE for optimizing electrical yield. These topics are covered in the following sections: ■ Overview ■ Optimization Statements ■ Optimization Examples Overview Optimization automatically generates model parameters and component values from a set of electrical specifications or measured data. When you define an optimization program and a circuit topology, HSPICE automatically selects the design components and model parameters to meet your DC, AC, and transient electrical specifications. The circuit-result targets are part of the .MEASURE command structure and you use a .MODEL statement to set up the optimization. Note: HSPICE uses post-processing output to compute the .MEASURE statements. If you set INTERP=1 to reduce the post-processing output, the measurement results might contain interpolation errors. See the HSPICE Reference Manual: Commands and Control Options for more information about these options. HSPICE employs an incremental optimization technique. This technique solves the DC parameters first, then the AC parameters, and finally the transient parameters. A set of optimizer measurement functions not only makes transistor optimization easy, but significantly improves cell and circuit optimization. HSPICE® User Guide: Simulation and Analysis B-2008.09 597 Chapter 24: Optimization Overview To perform optimization, create an input netlist file that specifies: ■ Minimum and maximum parameter and component limits. ■ Variable parameters and components. ■ An initial estimate of the selected parameter and component values. ■ Circuit performance goals or a model-versus-data error function. If you provide the input netlist file, optimization specifications, component limits, and initial guess, then the optimizer reiterates the circuit simulation until it either meets the target electrical specification, or finds an optimized solution. For improved optimization, reduced simulation time, and increased likelihood of a convergent solution, the initial estimate of component values should produce a circuit whose specifications are near those of the original target. This reduces the number of times the optimizer reselects component values and resimulates the circuit. Optimization Control How much time an optimization requires before it completes depends on: ■ Number of iterations allowed. ■ Relative input tolerance. ■ Output tolerance. ■ Gradient tolerance. The default values are satisfactory for most applications. Generally, 10 to 30 iterations are sufficient to obtain accurate optimizations. Simulation Accuracy For optimization, set the simulator with tighter convergence options than normal. The following are suggested options: For DC MOS model optimizations: absmos=1e-8 relmos=1e-5 relv=1e-4 For DC JFET, BJT, and diode model optimizations: 598 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 24: Optimization Overview absi=1e-10 reli=1e-5 relv=1e-4 For transient optimizations: relv=1e-4 relvar=1e-2 Curve Fit Optimization Use optimization to curve-fit DC, AC, or transient data: 1. Use the .DATA statement to store the numeric data for curves in the data file as in-line data. 2. Use the .PARAM xxx=OPTxxx statement to specify the variable circuit components and the parameter values for the netlist. The optimization analysis statements use the DATA keyword to call the inline data. 3. Use the .MEASURE statement to compare the simulation result to the values in the data file In this statement, use the ERR1 keyword to control the comparison. If the calculated value is not within the error tolerances specified in the optimization model, HSPICE selects a new set of component values. HSPICE then simulates the circuit again and repeats this process until it obtains the closest fit to the curve or until the set of error tolerances is satisfied. Goal Optimization Goal optimization differs from curve-fit optimization because it usually optimizes only a particular electrical specification, such as rise time or power dissipation. To specify goal optimizations, do the following: 1. Use the GOAL keyword. 2. In the .MEASURE statement, select a relational operator where GOAL is the target electrical specification to measure. HSPICE® User Guide: Simulation and Analysis B-2008.09 599 Chapter 24: Optimization Optimization Statements For example, you can choose a relational operator in multiple-constraint optimizations when the absolute accuracy of some criteria is less important than for others. Timing Analysis To analyze circuit timing violation, HSPICE uses a binary search algorithm. This algorithm generate a set of operational parameters, which produce a failure in the required behavior of the circuit. When a circuit timing failure occurs, you can identify a timing constraint, which can lead to a design guideline. Typical types of timing constraint violations include: ■ Data setup time before a clock. ■ Data hold time after a clock. ■ Minimum pulse width required to allow a signal to propagate to the output. ■ Maximum toggle frequency of the component(s). Bisection Optimization finds the value of an input variable (target value) associated with a goal value for an output variable. To relate them, you can use various types of input and output variables, such as voltage, current, delay time, or gain, and a transfer function. You can use the bisection feature in either a pass-fail mode or a bisection mode. In each case, the process is largely the same. Optimization Statements Optimization requires several statements: ■ .MODEL modname OPT ... ■ .PARAM parameter=OPTxxx (init, min, max) Use .PARAM statements to define initial, lower, and upper bounds. ■ A .DC, .AC, or .TRAN analysis statement, with: MODEL=modname OPTIMIZE=OPTxxx RESULTS=measurename Use .PRINT and .probe output statements, with the .DC, .AC, or .TRAN analysis statements. 600 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 24: Optimization Optimization Statements Only use an analysis statement with the OPTIMIZE keyword for optimization. To generate output for the optimized circuit, specify another analysis statement (.DC, .AC, or .TRAN), and the output statements. ■ .MEASURE measurename ... <GOAL=| < | > val> Include a space on either side of the relational operator: = <space> < <space> > <space> For a description of the types of .MEASURE statements that you can use in optimization, see Chapter 11, Simulation Output The proper specification order is: 1. Analysis statement with OPTIMIZE. 2. .MEASURE statements specifying optimization goals or error functions. 3. Ordinary analysis statement. 4. Output statements. Optimizing Analysis (.DC, .TRAN, .AC) The following syntax optimizes HSPICE simulation for a DC, AC, and Transient analysis. .DC <DATA=filename> SWEEP OPTIMIZE=OPTxxx + RESULTS=ierr1 ... ierrn MODEL=optmod .AC <DATA=filename> SWEEP OPTIMIZE=OPTxxx + RESULTS=ierr1 ... ierrn MODEL=optmod .TRAN <DATA=filename> SWEEP OPTIMIZE=OPTxxx + RESULTS=ierr1 ... ierrn MODEL=optmod Argument Description DATA Specifies an in-line file of parameter data to use in optimization. MODEL The optimization reference name, which you also specify in the .MODEL optimization statement. OPTIMIZE Indicates that the analysis is for optimization. Specifies the parameter reference name used in the .PARAM optimization statement. In a .PARAM optimization statements, if OPTIMIZE selects the parameter reference name, then the associated parameters vary during an optimization analysis. HSPICE® User Guide: Simulation and Analysis B-2008.09 601 Chapter 24: Optimization Optimization Examples Argument Description RESULTS The measurement reference name. You also specify this name in the .MEASURE optimization statement. RESULTS passes the analysis data to the .MEASURE optimization statement. Optimization Examples This section contains examples of HSPICE optimizations (for HSPICE RF optimization, see “Optimization” in the HSPICE RF Manual): ■ MOS Level 3 Model DC Optimization ■ MOS Level 13 Model DC Optimization ■ RC Network Optimization ■ Optimizing CMOS Tristate Buffer ■ BJT S-parameters Optimization ■ BJT Model DC Optimization ■ Optimizing GaAsFET Model DC ■ Optimizing MOS Op-amp MOS Level 3 Model DC Optimization This example shows an optimization of I-V data to a Level 3 MOS model. The data consists of gate curves (ids versus vgs) and drain curves (ids versus vds). This example optimizes the Level 3 parameters: ■ ■ GAMMA ■ UO ■ VMAX ■ THETA ■ 602 VTO KAPPA HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 24: Optimization Optimization Examples After optimization, HSPICE compares the model to the data for the gate, and then to the drain curves. .OPTION POST generates AvanWaves files for comparing the model to the data. Input Netlist File for Level 3 Model DC Optimization You can find the sample netlist for this example in the following directory: \$installdir/demo/hspice/devopt/ml3opt.sp The HSPICE input netlist shows: ■ Using .OPTION to tighten tolerances, which increases the accuracy of the simulation. Use this method for I-V optimization. ■ .MODEL optmod OPT itropt=30 limits the number of iterations to 30. ■ The circuit is one transistor. The VDS, VGS, and VBS parameter names, match names used in the data statements. ■ .PARAM statements specify XL, XW, TOX, and RSH process variation parameters, as constants. The device characterizes these measured parameters. ■ The model references parameters. In GAMMA= GAMMA, the left side is a Level 3 model parameter name; the right side is a .PARAM parameter name. ■ The long .PARAM statement specifies initial, min and max values for the optimized parameters. Optimization initializes UO at 480, and maintains it within the range 400 to 1000. ■ The first .DC statement indicates that: • • Parameters that you declared as OPT1 (in this example, all optimized parameters) are optimized. • The COMP1 error function matches the name of a .MEASURE statement. • ■ Data is in the in-line .DATA all block, which contains merged gate and drain curve data. The OPTMOD model sets the iteration limit. The .MEASURE statement specifies least-squares relative error. HSPICE divides the difference between data par(ids) and model i(m1) by the larger of: • the absolute value of par(ids), or • minval=10e-6 HSPICE® User Guide: Simulation and Analysis B-2008.09 603 Chapter 24: Optimization Optimization Examples If you use minval, low current data does not dominate the error. ■ Use the remaining .DC and .PRINT statements for print-back after optimization. You can place them anywhere in the netlist input file because parsing the file correctly assigns them. ■ The .PARAM VDS=0 VGS=0 VBS=0 IDS=0 statements declare these data column names as parameters. The .DATA statements contain data for IDS versus VDS, VGS, and VBS. Select data that matches the model parameters to optimize. Example To optimize GAMMA, use data with back bias (VBS= -2 in this case). To optimize KAPPA, the saturation region must contain data. In this example, the all data set contains: ■ Gate curves: vds=0.1 vbs=0,-2 vgs=1 to 5 in steps of 0.25. ■ Drain curves: vbs=0 vgs=2,3,4,5 vds=0.25 to 5 in steps of 0.25. Figure 100 shows the results. \$LEVEL 8 MOSFET OPTIMIZATION APRIL 22, 2004 4:58:09 OPTLEVELS.90 IM ANP [LIN] 381.270U 300.0U IO 200.0U 100.0U 0 1.0 1.50 2.0 2.5 3.0 YOS [LIN] 3.5 4.0 4.50 5.0 ANP [LIN] 5.0M OPTLEVELS.90 IM 4.0M IO 3.0M 2.0M 1.0M 250.0N 1.0 2.0 3.0 4.0 5.0 YOS [LIN] Figure 100 Level 3 MOSFET Optimization 604 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 24: Optimization Optimization Examples MOS Level 13 Model DC Optimization This example shows I-V data optimization to a Level 13 MOS model. The data consists of gate curves (ids versus vgs) and drain curves (ids versus vds). This example demonstrates two-stage optimization. 1. HSPICE optimizes the vfb0, k1, muz, x2m, and u00 Level 13 parameters to the gate data. 2. HSPICE optimizes the MUS, X3MS, and U1 Level 13 parameters, and the ALPHA impact ionization parameter to the drain data. After optimization, HSPICE compares the model to the data. The POST option generates AvanWaves files to compare the model to the data. Figure 101 on page 605 shows the results. DC Optimization Input Netlist File for Level 13 Model You can find the sample netlist for this example in the following directory: \$installdir/demo/hspice/mos/ml13opt.sp. ANPORT.SP MOS OPERATIONAL AMPLIFIER OPTIMIZATION APRIL 22, 2003 5:21:26 MLLSOPT.SV0 IM ANP [LIN] 300.0U IO 200.0U 100.0U 0 1.0 1.50 2.0 2.5 3.0 YOS [LIN] 3.5 4.0 4.50 5.0 MLLSOPT.SV1 IM ANP [LIN] 4.9787M 4.0M IO 3.0M 2.0M 1.0M 250.0M 1.0 2.0 YOS [LIN] 3.0 4.0 5.0 Figure 101 Level 13 MOSFET Optimization HSPICE® User Guide: Simulation and Analysis B-2008.09 605 Chapter 24: Optimization Optimization Examples RC Network Optimization The following example optimizes the power dissipation and time constant for an RC network. The circuit is a parallel resistor and capacitor. Design targets are: ■ 1 s time constant. ■ 50 mW rms power dissipation through the resistor. The HSPICE strategy is: ■ RC1 .MEASURE calculates the RC time constant, where the GOAL of .3679 V corresponds to 1 s time constant e-rc. ■ RC2 .MEASURE calculates the rms power, where the GOAL is 50 mW. ■ OPTRC identifies RX and CX as optimization parameters, and sets their starting, minimum, and maximum values. Network optimization uses these HSPICE features: ■ Measure voltages and report times that are subject to a goal. ■ Measure device power dissipation subject to a goal. ■ Measure statements replace the tabular or plot output. ■ Parameters used as element values. ■ Parameter optimizing function. ■ Transient analysis with SWEEP optimizing. Optimization Results RESIDUAL SUM OF SQUARES NORM OF THE GRADIENT MARQUARDT SCALING PARAMETER NO. OF FUNCTION EVALUATIONS NO. OF ITERATIONS = 9 = 4.291583E-16 = 5.083346E-04 = 2.297208E-04 = 20 Residual Sum of Squares: The residual sum of squares is a measure of the total error. The smaller this value is the more accurate the optimization results are. ne residual sum of squares= ∑ Ei 2 i=1 606 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 24: Optimization Optimization Examples In this equation, E is the error function, and ne is the number of error functions. Norm of the Gradient: The norm of the gradient is another measure of the total error. The smaller this value is the more accurate the optimization results are. The following equations calculates the G gradient: ne Gj = ∑ Ei ⋅ ( ΔE i ⁄ ΔP j ) i=1 np norm of the gradient= 2 ⋅ ∑ Gj 2 i=1 In this equation, P is the parameter, and np is the number of parameters to optimize. Marquardt Scaling Parameter: The Levenburg-Marquardt algorithm uses this parameter to find the actual solution for the optimizing parameters. The search direction is a combination of the Steepest Descent method and the Gauss-Newton method. The optimizer initially uses the Steepest Descent method as the fastest approach to the solution. It then uses the Gauss-Newton method to find the solution. During this process, the Marquardt Scaling Parameter becomes very small, but starts to increase again if the solution starts to deviate. If this happens, the optimizer chooses between the two methods to work toward the solution again. If the optimizer does not attain the optimal solution, it prints both an error message, and a large Marquardt Scaling Parameter value. Number of Function Evaluations: This is the number of analyses (for example, finite difference or central difference) needed to find a minimum of the function. Number of Iterations: This is the number of iterations needed to find the optimized or actual solution. HSPICE® User Guide: Simulation and Analysis B-2008.09 607 Chapter 24: Optimization Optimization Examples Optimized Parameters OPTRC .param rx= 7.4823 .param cx=133.9934m \$ \$ 55.6965 44.3035 5.7945m 5.1872m *FILE: RCOPT.SP OPTIMIZE THE POWER DISSIPATION AND TIME CONSTANT APRIL 22, 2004 5:38:12 998.587N RCOPT.TR0 1 900.0N RCOPT.TR1 1 800.0N VOLT [LIN] 700.0N 600.0N 500.0N 400.0N 300.0N 200.0N 100.0N 929.90U 0 200.0M 400.0M 600.0M TIME [LIN] 800.0M 1.0 Figure 102 Power Dissipation and Time Constant (VOLT) RCOPT.TR0=Before Optimization, RCOPT.TR1=Optimized Result 608 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 24: Optimization Optimization Examples *FILE: RCOPT.SP OPTIMIZE THE POWER DISSIPATION AND TIME CONTSTANT APRIL 22, 2004 5:38:12 RCOPT.TR0 PIR1 1.80 RCOPT.TR1 PIR1 1.60 MATT [LIN] 1.40 1.20 1.0 800.0M 600.0M 400.0M 200.0M 0 0 200.0N 400.0N 600.0N TIME [LIN] 800.0N 1.0 Figure 103 Power Dissipation and Time Constant (WATT) RCOPT.TR0=Before Optimization, RCOPT.TR1=Optimized Result Optimizing CMOS Tristate Buffer The example circuit is an inverting CMOS tristate buffer. The design targets are: ■ Rising edge delay of 5 ns (input 50% voltage to output 50% voltage). ■ Falling edge delay of 5 ns (input 50% voltage to output 50% voltage). ■ RMS power dissipation should be as low as possible. ■ Output load consists of: • pad capacitance • leadframe inductance • 50 pF capacitive load The HSPICE strategy is: HSPICE® User Guide: Simulation and Analysis B-2008.09 609 Chapter 24: Optimization Optimization Examples ■ Simultaneously optimize both the rising and falling delay buffer. ■ Set up the internal power supplies, and the tristate enable as global nodes. ■ Optimize all device widths except: • Initial inverter (assumed to be standard size). • Tristate inverter and part of the tristate control (optimizing is not sensitive to this path). ■ Perform an initial transient analysis for plotting purposes. Then optimize and perform a final transient analysis for plotting. ■ To use a weighted RMS power measure, specify unrealistically-low power goals. Then use MINVAL to attenuate the error. Input Netlist File to Optimize a CMOS Tristate Buffer You can find the sample netlist for this example in the following directory: \$installdir/demo/hspice/apps/trist_buf_opt.sp 610 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 24: Optimization Optimization Examples VCC VCC VCC VCC MP1 DATAN MP3 MP2 PEN BUS MP11 MP10 Cbus MN1 VCC VCC NENN MN3 MN2 MN12 MP12 VCC Cext PENN Cpad MP4 MN10 MN11 NEN MN5 MN4 ENB VCC MP13 ENBN Cenbn Cenb MN13 Figure 104 Tristate Buffer Optimization Circuit HSPICE® User Guide: Simulation and Analysis B-2008.09 611 Chapter 24: Optimization Optimization Examples * TRI-STATE I/O OPTIMIZATION APRIL 22, 2003 5:52:46 5.0 ASIC2.TR1 OUT 4.50 OUTBAR 4.0 ASIC2.TR0 OUT VOLT [LIN] 3.50 OUTBAR 3.0 2.50 2.0 1.50 1.0 500.0N 0 0 2.0N 4.0N 6.0N 8.0N TIME [LIN] 10.0N 12.0N 14.0N 15.0N Figure 105 Tristate Input/Output Optimization ACIC2B.TR0 = Before Optimization, ACIC2B.TR1=Optimized Result BJT S-parameters Optimization The following example optimizes the S-parameters to match those specified for a set of measurements. The .DATA measured in-line data statement contains these measured S-parameters as a function of frequency. The model parameters of the microwave transistor (LBB, LCC, LEE, TF, CBE, CBC, RB, RE, RC, and IS) vary. As a result, the measured S-parameters (in the .DATA statement) match the calculated S-parameters from the simulation results. This optimization uses a 2n6604 microwave transistor, and an equivalent circuit that consists of a BJT, with parasitic resistances and inductances. The BJT is biased at a 10 mA collector current (0.1 mA base current at DC bias and bf=100). 612 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 24: Optimization Optimization Examples Key HSPICE Features Used ■ .NET command to simulate network analyzer action. ■ .AC optimization. ■ Optimized element and model parameters. ■ Optimizing, compares measured S-parameters to calculated parameters. ■ S-parameters used in magnitude and phase (real and imaginary available). ■ Weighting of data-driven frequency versus S Parameter table. Used for the phase domain. Input Netlist File for Optimizing BJT S-parameters BJT Equivalent Circuit Input Use the bjtopt.sp netlist file located in your \$<installdir>/demo/hspice/devopt directory for optimizing BJT S-parameters. Optimization Results RESIDUAL SUM OF SQUARES =5.142639e-02 NORM OF THE GRADIENT =6.068882e-02 MARQUARDT SCALING PARAMETER=0.340303 CO. OF FUNCTION EVALUATIONS=170 NO. OF ITERATIONS =35 The maximum number of iterations (25) was exceeded. However, the results probably are accurate. Increase ITROPT accordingly. Optimized Parameters OPT1– Final Values ***OPTIMIZED PARAMETERS OPT1 SENS %NORM-SEN .PARAM LBB = 1.5834N \$ 27.3566X 2.4368 .PARAM LCC = 2.1334N \$ 12.5835X 1.5138 .PARAM LEE =723.0995P \$254.2312X 12.3262 .PARAM TF =12.7611P \$ 7.4344G 10.0532 .PARAM CBE =620.5195F \$ 23.0855G 1.5300 .PARAM CBC = 1.0263P \$346.0167G 44.5016 .PARAM RB = 2.0582 \$ 12.8257M 2.3084 .PARAM RE =869.8714M \$ 66.8123M 4.5597 .PARAM RC =54.2262 \$ 3.1427M 20.7359 .PARAM IS =99.9900P \$ 3.6533X 34.4463M HSPICE® User Guide: Simulation and Analysis B-2008.09 613 Chapter 24: Optimization Optimization Examples FILE: BJTOPT.SP NETWORK S-PARAMETER OPTIMIZATION APRIL 22, 2004 6:22:34 20.0 10.0 1.9879 650.0N [LIN] 600.0N 550.0N 500.0N 450.0N 400.0N 96.8250N 50.0N 20.0N 100.0X 500.0X 1.08 1.508 2.06 HERTZ [LIN] Figure 106 BJT-S Parameter Optimization BJT Model DC Optimization The goal is to match forward and reverse Gummel plots obtained from a HP4145 semiconductor analyzer by using the HSPICE LEVEL=1 GummelPoon BJT model. Because Gummel plots are at low base currents, HSPICE does not optimize the base resistance. HSPICE also does not optimize forward and reverse Early voltages (VAF and VAR) because simulation does not measure VCE data. The key feature in this optimization is incremental optimization. 1. HSPICE first optimizes the forward-Gummel data points. 2. HSPICE updates forward-optimized parameters into the model. 614 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 24: Optimization Optimization Examples After updating, you cannot change these parameters. 3. HSPICE next optimizes the reverse-Gummel data points. BJT Model DC Optimization Input Netlist File You can find the sample netlist for this example in the following directory: \$installdir/demo/hspice/devopt/opt_bjt.sp *FILE: OPT_BJT.SP BJT OPTIMIZATION T2N9547 APRIL 22, 2004 17:42:41 OPT_BJT.SV0 I2IQ1 10.0N PARIIB 1.0N I1IQ1 AMP 2 LOW PARIIC 100.0U 10.0U 1.0U 100.0M 10.0M 1.0M 100.0P 400.0M 500.0M 600.0M BASEF [LIN] 700.0M 800.0M 820.0M Figure 107 BJT Optimization Forward Gummel Plots HSPICE® User Guide: Simulation and Analysis B-2008.09 615 Chapter 24: Optimization Optimization Examples *FILE: OPT_BJT.SP BJT OPTIMIZATION T2N9547 APRIL 22, 2004 17:42:41 OPT_BJT.SV1 I2IQ1 10.0N PARIIB 1.0N I1IQ1 PARIIC AMP 2 LCV 100.0U 10.0U 1.0U 100.0M 10.0M 1.0M 100.0P 200.0M 300.0M 400.0M 500.0M BASER [LIN] 600.0M 700.0M 800.0M Figure 108 BJT Optimization Reverse Gummel Plots Optimizing GaAsFET Model DC This example circuit is a high-performance, GaAsFET transistor. The design target is to match HP4145 DC measured data to the HSPICE LEVEL=3 JFET model. The HSPICE strategy is: ■ ■ 616 .MEASURE IDSERR is an ERR1 type function. It provides linear attenuation of the error results starting at 20 mA. This function ignores all currents below 1 mA. The high-current fit is the most important for this model. The OPT1 function simultaneously optimizes all DC parameters. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 24: Optimization Optimization Examples ■ The .DATA statement merges TD1.dat and TD2.dat data files. ■ The graph plot model sets the MONO=1 parameter to remove the retrace lines from the family of curves. GaAsFET Model DC Optimization Input Netlist File You can find the sample netlist for this example in the following directory: \$installdir/demo/hspice/devopt/jopt.sp *FILE: JOPT.SP JFET OPTIMIZATION APRIL 22, 2004 18:41:12 45.0M 40.0M PARAM [LIN] 35.0M 30.0M 25.0M 20.0M 15.0M 10.0M 5.0M 0 0 1.0 2.0 DESIRED [LIN] 3.0 4.0 Figure 109 JFET Optimization Optimizing MOS Op-amp The design goals for the MOS operational amplifier are: HSPICE® User Guide: Simulation and Analysis B-2008.09 617 Chapter 24: Optimization Optimization Examples ■ Minimize the gate area (and therefore the total cell area). ■ Minimize the power dissipation. ■ Open-loop transient step response of 100 ns for rising and falling edges. The HSPICE strategy is: ■ Simultaneously optimize two amplifier cells for rising and falling edges. ■ Total power is power for two cells. ■ The optimization transient analysis must be longer to allow for a range of values in intermediate results. ■ All transistor widths and lengths are optimized. ■ Calculate the transistor area algebraically use a voltage value and minimize the resulting voltage. ■ The transistor area measure statement uses MINVAL, which assigns less weight to the area minimization. ■ Optimizes the bias voltage. Example: MOS Op-amp Optimization Input Netlist File You can find the sample netlist for this example in the following directory: \$installdir/demo/hspice/ciropt/ampopt.sp 618 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 24: Optimization Optimization Examples vsupply M4 M3 M6 vout vin- M1 vbias M2 vin+ M5 M7 Figure 110 CMOS Op-amp HSPICE® User Guide: Simulation and Analysis B-2008.09 619 Chapter 24: Optimization Optimization Examples AMPORT.SP MOS OPERATIONAL AMPLIFIER OPTIMIZATION APRIL 22, 2004 18:57:06 3.9877 3.0 VOLT [LIN] 2.0 1.0 6.40M 6.20M 6.0M 5.80M 5.60M 5.40M 0 25.0N 50.0N 75.0N 100.0N 125.0N 150.0N TIME [LIN] Figure 111 Operational Amplifier Optimization 620 HSPICE® User Guide: Simulation and Analysis B-2008.09 25 25 RC Reduction and Post-Layout Simulation Describes RC network reduction in HSPICE and post-layout simulation containing a large number of parasitic elements. In HSPICE, the post-layout simulation is similar to pre-layout simulation. You can do the post-layout simulation with DSPF only if it is a fully extracted netlist with instances. The DSPF file can be included to the pre-layout netlist. You will need to replace the ideal .SUBCKT blocks from your original netlist with .SUBCKT blocks containing the extracted parasitics. Remember to verify that the port order in the extracted .SUBCKT blocks match the port order in the ideal netlist. If your extracted netlist is not too large (approximately 100,000 elements or fewer), then HSPICE can give you very results. Otherwise, you can also employ an RC reduction. These topics are covered in the following sections: ■ Linear Acceleration ■ Linear Acceleration Control Options Summary Linear Acceleration By using the SIM_LA option, you can accelerate the simulation of circuits that include large linear RC networks. To achieve this acceleration, HSPICE linearly reduces all matrices that represent RC networks. The result is a smaller matrix that maintains the original port behavior, yet achieves significant savings in memory and computation. Thus, the SIM_LA option is ideal for circuits with large numbers of resistors and capacitors, such as clock trees, power lines, or substrate networks. In general, the RC elements are separated into their own network. The nodes shared by both main circuit elements (including .PRINT, .PROBE, and HSPICE® User Guide: Simulation and Analysis B-2008.09 621 Chapter 25: RC Reduction and Post-Layout Simulation Linear Acceleration .MEASURE statements), and RC elements are the port nodes of the RC network. All other RC nodes are internal nodes. The currents flowing into the port nodes are a frequency-dependent function of the voltages at those nodes. The multiport admittance of a network represents this relationship. ■ The SIM_LA option formulates matrices to represent multiport admittance. ■ Then, to eliminate as many internal nodes as possible, it reduces the size of these matrices, while preserving the admittance, otherwise known as port node behavior. ■ The amount of reduction depends on the f0 upper frequency, the threshold frequency where SIM_LA preserves the admittance. This is shown graphically in Figure 112. admittance ce ta n mit ad ual approx act f0 frequency Figure 112 Multiport Admittance vs. Frequency The SIM_LA option is very effective for post-layout simulation because of the volume of parasitics. For frequencies below f0, the approx signal matches that of the original admittance. Above f0, the two waveforms diverge, but the higher frequencies are not of interest. The lower the f0 frequency, the greater the amount of reduction. For the syntax and description of this control option, see .OPTION SIM_LA in the HSPICE Reference Manual: Commands and Control Options. You can choose one of two algorithms, explained in the following sections: ■ ■ 622 PACT Algorithm PI Algorithm HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 25: RC Reduction and Post-Layout Simulation Linear Acceleration PACT Algorithm The PACT (Pole Analysis via Congruence Transforms) algorithm reduces the RC networks in a well-conditioned manner, while preserving network stability. ■ The transform preserves the first two moments of admittance at DC (slope and offset), so that DC behavior is correct (see Figure 113). ■ The algorithm preserves enough low-frequency poles from the original network to maintain the circuit behavior up to a specified maximum frequency f0, within the specified tolerance. This approach is more accurate between these two algorithms, and is the default. admittance d rve se re tp fse f do an nce itta pe dm slo al a ctu a PACT: poles added f0 frequency Figure 113 PACT Algorithm PI Algorithm This algorithm creates a pi model of the RC network. ■ For a two-port, the pi model reduced network consists of: • a resistor connecting the two ports, and • a capacitor connecting each port to ground HSPICE® User Guide: Simulation and Analysis B-2008.09 623 Chapter 25: RC Reduction and Post-Layout Simulation Linear Acceleration Control Options Summary The result resembles the Greek letter pi. ■ For a general multiport, SIM_LA preserves the DC admittance between the ports, and the total capacitance that connects the ports to ground. All floating capacitances are lumped to ground. Linear Acceleration Control Options Summary In addition to SIM_LA, other options are available to control the maximum resistance and minimum capacitance values to preserve, and to limit the operating parameters of the PACT algorithm. Table 65 contains a summary of these control options. For their syntax and descriptions, see the respective option descriptions in Chapter 3, HSPICE and RF Netlist Simulation Control Options, in the HSPICE Reference Manual: Command and Control Options. Table 65 PACT Options Syntax Description .OPTION SIM_LA=PACT | PI Activates linear matrix reduction and selects between two methods. .OPTION LA_FREQ=value Upper frequency where you need accuracy preserved. value is the upper frequency for which the PACT algorithm preserves accuracy. If value is 0, PACT drops all capacitors because only DC is of interest. The maximum frequency required for accurate reduction depends on both the technology of the circuit and the time scale of interest. In general, the faster the circuit, the higher the maximum frequency. The default is 1GHz. .OPTION LA_MAXR=value Maximum resistance for linear matrix reduction. value is the maximum resistance preserved in the reduction. SIM_LA assumes that any resistor greater than value has an infinite resistance, and drops the resistor after reduction finishes. The default is 1e15 ohms. .OPTION LA_MINC=value Minimum capacitance for linear matrix reduction. value is the minimum capacitance preserved in the reduction. After reduction completes, SIM_LA lumps any capacitor smaller than value to ground. The default is 1e-16 farads. 624 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 25: RC Reduction and Post-Layout Simulation Linear Acceleration Control Options Summary Table 65 PACT Options (Continued) Syntax Description .OPTION LA_TIME=value Minimum time for which accuracy must be preserved. value is the minimum switching time for which the PACT algorithm preserves accuracy. HSPICE does not accurately represent waveforms that occur more rapidly than this time. LA_TIME is simply the dual of LA_FREQ. The default is 1ns, equivalent to setting LA_FREQ=1GHz. .OPTION LA_TOL=value Error tolerance for the PACT algorithm. value is the error tolerance for the PACT algorithm, is between 0.0 and 1.0. The default is 0.05. Example In this example, the circuit has a typical risetime of 1ns. Set the maximum frequency to 1 GHz, or set the minimum switching time to 1ns. .OPTION LA_FREQ = 1GHz -or.OPTION LA_TIME = 1ns However, if spikes occur in 0.1ns, HSPICE will not accurately simulate them. To capture the behavior of the spikes, use: .OPTION LA_FREQ = 10GHz -or.OPTION LA_TIME = 0.1ns Note: Higher frequencies (smaller times) increase accuracy, but only up to the minimum time step used in HSPICE. Supporting Parasitic L- and K-elements HSPICE supports simulation with parasitic L- and K-elements. You need to set the minimum value of mutual inductance using the KLIM option. The default value of KLIM is 10mH. The second-order mutual inductance is not calculated for values less than KLIM, but parasitic mutual inductance values can be many orders smaller than the default value. HSPICE® User Guide: Simulation and Analysis B-2008.09 625 Chapter 25: RC Reduction and Post-Layout Simulation Linear Acceleration Control Options Summary Also, note that RC reduction will not be very effective with respect to L- and Kelements. If you increase the simulation speed of your netlist having a huge number of parasitic elements, you need to properly understand the accuracy versus speed trade-off. For more information about the KLIM option, see .OPTION KLIM in the HSPICE Reference Manual: Commands and Control Options. 626 HSPICE® User Guide: Simulation and Analysis B-2008.09 26 MOSFET Model Reliability Analysis (MOSRA) 26 Describes the procedures for HSPICE MOSFET reliability analysis (MOSRA). These topics are covered in the following sections: ■ Overview ■ .MOSRA, .MOSRAPRINT, .MODEL, and .APPENDMODEL Commands Overview As CMOS technology is scaled down, reliability requirements become both more challenging and more important in maintaining the long-term reliability of these devices. Two of the most critical reliability issues, effects due to the hot carrier injection (HCI) and the negative bias temperature instability (NBTI) can change the characteristics of MOS devices. HSPICE reliability analysis allows circuit designers to predict the reliability of their design to allow enough margin for their circuits to function correctly over their lifetime. A unified custom reliability modeling MOSRA API is available. Contact your Synopsys technical support team for more information. Usage Model HSPICE reliability analysis (or HCI and NBTI analysis), is always a two-phase simulation: the fresh simulation phase and the post-stress simulation phase. HSPICE® User Guide: Simulation and Analysis B-2008.09 627 Chapter 26: MOSFET Model Reliability Analysis (MOSRA) Overview ■ Fresh simulation phase: HSPICE computes the electron age/stress of selected MOS transistors in the circuit based on circuit behavior and HSPICE built-in stress model including HCI and/or NBTI effect. ■ Post-stress simulation phase: HSPICE simulates the degradation effect on circuit performance, based on the stress information produced during the fresh simulation phase. Beginning with the A-2007.09 release, the HSPICE MOSRA feature supports the following HSPICE MOSFET levels: Level 49, Level 53, Level 54, Level 57, Level 66, Level 70, and Level 71, and external CMI MOSFET models. The HSPICE reliability analysis process is presented in Figure 114. Pre-stress (fresh_device) Simulation Phase Original Model Card Pre-stress Simulation results Stress Integration Netlist MOSRA Model Card Conversion of stress into device parameter degradation Post-Stress (aged_device) Simulation Post-stress Simulation results Figure 114 HSPICE Reliability Simulation Flow Example Setup The following example file demonstrates how to set up a HSPICE reliability reliability analysis. 628 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 26: MOSFET Model Reliability Analysis (MOSRA) .MOSRA, .MOSRAPRINT, .MODEL, and .APPENDMODEL Commands * MOSRA TEST vdd 1 0 2 mp1 3 2 1 1 p1 mn1 3 2 0 0 n1 mp2 4 3 1 1 p1 mn2 4 3 0 0 n1 mp3 2 4 1 1 p1 mn3 2 4 0 0 n1 c1 2 0 .1p l=0.1u l=0.1u l=0.1u l=0.1u l=0.1u l=0.1u w=10u ad=5p pd=6u as=5p ps=6u w=5u ad=5p pd=6u as=5p ps=6u w=10u ad=5p pd=6u as=5p ps=6u w=5u ad=5p pd=6u as=5p ps=6u w=10u ad=5p pd=6u as=5p ps=6u w=5u ad=5p pd=6u as=5p ps=6u .model p1 pmos level=54 version=4.5 .model n1 nmos level=54 version=4.5 .model p1_ra mosra level=1 +tit0 = 5e-8 titfd = 7.5e-10 +tn = 0.25 tittd = 1.45e-20 .appendmodel p1_ra mosra p1 pmos .mosra reltotaltime=1e8 .ic v(2)=2 .tran .1ps 5ns .options post .end .MOSRA, .MOSRAPRINT, .MODEL, and .APPENDMODEL Commands The following are descriptions of the command syntax and arguments for the .MOSRA, MOSRAPRINT, . MODEL, and .APPENDMODEL statements. .MOSRA Starts HSPICE HCI and/or NBTI reliability analysis. Syntax .MOSRA RelTotalTime=time_value + [RelStartTime=time_value] [DEC=value] [LIN=value] + [RelStep=time_value] [RelMode=0|1|2] SimMode=[0|1|2] + [AgingStart=time_value] [AgingStop=time_value] + [AgingPeriod=time_value] [AgingWidth=time_value] + [AgingInst="inst_name"] + [HciThreshold=value] [NbtiThreshold=value] + [Integmod=0|1|2] [Xpolatemod=0|1|2] + [Tsample1=value] [Tsample2=value] HSPICE® User Guide: Simulation and Analysis B-2008.09 629 Chapter 26: MOSFET Model Reliability Analysis (MOSRA) .MOSRA, .MOSRAPRINT, .MODEL, and .APPENDMODEL Commands Argument Description RelTotalTime Defines final reliability test time to use in post stress simulation phase. Required argument. RelStartTime Time point of the first post-stress simulation. Default is 0. DEC Specifies number of post-stress time points simulated per decade. LIN Specifies the linear post-stress time points from RelStartTme to RelTotalTime. RelStep Performs post-stress simulation phase on time= RelStep, 2* RelStep, 3* RelStep, … until it achieves the RelTotalTime; the default is equal to RelTotalTime. Value is ignored if DEC or LIN value is set. RelMode Selects whether a simulation accounts for both HCI and NBTI effects or either one of them. If RelMode in the .MOSRA command is not set or set to 0, then the RelMode inside individual MOSRA models takes precedence for that MOSRA model only; the rest of the MOSRA models take the RelMode value from the .MOSRA command. If any other value except 0, 1, or 2 is set, a warning message is issued, and RelMode is set to default value 0. The RelMode parameter is also available in the MOSRA model card with additional restrictions. ■ ■ ■ SimMode 0: both HCI and NBTI, Default. 1: HCI only 2: NBTI only ■ 0: Select pre-stress simulation only 1: Select post-stress simulation only ■ 2: Select both pre- and post-stress simulation If set to 1, HSPICE reads in the *.radeg0 file for post-stress simulation and uses it to update the input for reliability analysis; the transient output is in a *.tr1 waveform file. The *.radeg file should be in the same directory as the input netlist. ■ When SimMode =1, the netlist stimuli can be different from the SimMode=0 netlist that generated the *.radeg file. AgingStart 630 Optionally defines time when HSPICE starts stress effect calculation during transient simulation. Default is 0.0. HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 26: MOSFET Model Reliability Analysis (MOSRA) .MOSRA, .MOSRAPRINT, .MODEL, and .APPENDMODEL Commands Argument Description AgingStop Optionally defines time when HSPICE stops stress effect calculation during transient simulation. Default is tstop in .TRAN statement. AgingPeriod Specifies the stress period; scales the total degradation over time. AgingWidth The AgingWidth (circuit time “on”) argument works with the AgingPeriod argument. For example: if you specify AgingPeriod=1.0s and AgingWidth=0.5s, then the circuit will be turned on for 0.5s, then be turned off for 0.5s. (The period is 1.0s.) HciThreshold Optionally used in post stress simulation; this argument allows you to define whether the HCI effect is accounted for in a particular transistor, based on the specified HCI threshold value. Default is 0.0 NbtiThreshold Optionally used in post stress simulation; this argument allows you to define whether the NBTI effect will be accounted for in a particular transistor, based on this threshold value. Default is 0.0 AgingInst Selected MOSFET devices to which HSPICE applies HCI and/or NBTI analysis. The default is all MOSFET devices with reliability model appended. The name must be surrounded by quotes. Multiple names are allowed, and wildcards are supported. Integmod The flag is used to select the integration method and function. ■ ■ ■ Xpolatemod 0 (default): call the MOSRAAPI integration function 1: True derivation and integration method 2: Linearization and integration method (support non-constant n coefficient) The flag is used to select the extrapolation method and function. ■ ■ ■ 0 (default): call the MOSRAAPI extrapolation function 1: Linearization extrapolation method (support non-constant n coefficient) 2: Aeff/Neff extraction and extrapolation method Tsample1 First simulation time point of stress_total sampling for Aeff/Neff extraction Tsample2 Second simulation time point of stress_total sampling for Aeff/Neff extraction HSPICE® User Guide: Simulation and Analysis B-2008.09 631 Chapter 26: MOSFET Model Reliability Analysis (MOSRA) .MOSRA, .MOSRAPRINT, .MODEL, and .APPENDMODEL Commands Description Use the .MOSRA command to initiate HCI and NBTI analysis. This is a twophase simulation, the fresh simulation phase and the post stress simulation phase. During the fresh simulation phase, HSPICE computes the electron age/ stress of selected MOS transistors in the circuit based on circuit behavior and the HSPICE built-in stress model including HCI and/or NBTI effect. During the post stress simulation phase, HSPICE simulates the degradation effect on circuit performance, based on the stress information produced during the fresh simulation phase. If either DEC or LIN is specified, the RelStep value is ignored. See Figure 115 on page 633 for an illustration of the .MOSRA command/syntax. Example .mosra reltotaltime=6.3e+8 relstep=6.3e+7 + agingstart=5n agingstop=100n + hcithreshold=0 nbtithreshold=0 + aginginst="x1.*" 632 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 26: MOSFET Model Reliability Analysis (MOSRA) .MOSRA, .MOSRAPRINT, .MODEL, and .APPENDMODEL Commands Command/syntax for HSPICE reliability simulation (1/3) Simulation Transient time = 100ns Stress evaluation & integral 2*RelStep 100ns 100ns * 2 100ns * 3 …... RelStep 3*RelStep RelTotalTime Stresstotal (reported in .radeg output file) .MOSRA Reltotaltime = 1e+9 RelStep= 1e+8 .Tran 1n 100ns Command/syntax for HSPICE reliability simulation (2/3) AgingPeriod = 1s Default: tstop in .tran Simulation Transient time Circuit off time Stress evaluation & integral 2*RelStep 10ns AgingStart Default: 0 100ns AgingStop Default: tstop in .tran 1s 2s 3s ………… RelStep 3*RelStep RelTotalTime Stresstotal (reported in .radeg output file) .MOSRA Reltotaltime = 1e+9 RelStep= 1e+8 AgingStart=10ns AgingStop=100nS AgingPeriod=1s .Tran 1n 100ns Command/syntax for HSPICE reliability simulation (3/3) AgingPeriod = 1s Default: tstop in .tran Agingwidth = 0.5s Default: tstop in .tran Circuit on time Circuit off time Simulation Transient time Stress evaluation & integral 2*RelStep 0ns 100ns 200ns 300ns 0.5s 1s RelStep 3*RelStep RelTotalTime Stresstotal (reported in .radeg output file) .MOSRA Reltotaltime = 1e+9 RelStep= 1e+8 + AgingPeriod=1s Agingwidth= 0.5s .Tran 1n 100ns Figure 115 Graphic Illustration of MOSRA Command/Syntax HSPICE® User Guide: Simulation and Analysis B-2008.09 633 Chapter 26: MOSFET Model Reliability Analysis (MOSRA) .MOSRA, .MOSRAPRINT, .MODEL, and .APPENDMODEL Commands .MOSRAPRINT Provides .PRINT/.PROBE usage to the .MOSRA command. Syntax .MOSRAPRINT output_name output_type(element_name, vds=exp1, vgs=exp2, vbs=exp3) Argument Description output_nam User-defined output variable; this output_name@element_name is used as the as output variable name in the output file. output_type Can be one of output variable types vth, gm, gds, or ids. element_name Output variable name in the output file. Definition This command provides measurement functionary to the .MOSRA command. This syntax prints the Ids value of the mosfet at the final reliability test time. There is no order requirement for vds, vgs, and vbs. The wildcards '?' and '*' can be used in element_name. The output file format is the same as the measurement file format. The extension file name for this file is *.ra#. Example The following syntax prints the Ids value of the mosfet m1, when vds = 5 vgs= 5, vbs = 0, at the reltime point. .MOSRA reltotaltime=5e+7 relstep=1e+7 .MOSRAPRINT ids(m1, vds=5, vgs=5, vbs=0) .MODEL Syntax .model mname mosra + level=value + [RelMode=0|1|2] 634 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 26: MOSFET Model Reliability Analysis (MOSRA) .MOSRA, .MOSRAPRINT, .MODEL, and .APPENDMODEL Commands + <relmodelparam> Argument Description mname User-defined MOSFET reliability model name mosra HSPICE model type name for MOSFET reliability model level (alias: mosralevel) To use the Synopsys MOSRA model, set LEVEL=1. For compatibility with HSIM, in the .MODEL statement, 'LEVEL=' can be replaced with 'MOSRALEVEL='. HSPICE will consider them equivalent. Example: The following two lines will be interpreted the same by HSPICE. .MODEL my_mod MOSRA LEVEL=1 .MODEL my_mod MOSRA MOSRALEVEL=1 To use custom MOSRA models and for discussion of LEVEL values, refer to the HSPICE Application Note: Unified Custom Reliability Modeling API (MOSRA API). Contact your Synopsys technical support team for more information. RelMode HSPICE reliability mode level; selects whether a simulation accounts for both HCI and NBTI effects or either one of them. If the RelMode in the .MOSRA command is defined as 1 or 2, it takes higher priority and applies to all MOSRA models. If RelMode in the .MOSRA command is not set or set to 0, then the RelMode inside individual MOSRA models take precedence for that MOSRA model only; the rest of the MOSRA models take the RelMode value from the .MOSRA command. If any other value is set, except 0, 1, or 2, a warning is issued, and RelMode is automatically set to the default value 0. ■ ■ ■ relmodelparam 0: both HCI and NBTI, Default. 1: HCI only 2: NBTI only Reliability model parameter for HCI and NBTI. See the following sections for HCI and NBTI parameters. HSPICE® User Guide: Simulation and Analysis B-2008.09 635 Chapter 26: MOSFET Model Reliability Analysis (MOSRA) .MOSRA, .MOSRAPRINT, .MODEL, and .APPENDMODEL Commands Synopsys LEVEL1 mosra model, NBTI for PMOS Vth degradation Table 66 NBTI for PMOS Vth degradation Parameter Default tit0 5e-7 First parameter for interface trap inducing threshold voltage degradation titce 0 Inversion charge exponent for interface trap inducing threshold voltage degradation titfd 7.5e-10 Oxide electric field dependence for interface trap inducing threshold voltage degradation titlc 0 Channel length coefficient for oxide trap inducing threshold voltage degradation title 0 Channel length exponent for oxide trap inducing threshold voltage degradation tittd 1.45e-20 Temperature dependent component of interface trap inducing threshold voltage degradation titwc 0 Channel width coefficient for interface trap inducing threshold voltage degradation titwe 0 Channel width exponent for interface trap inducing threshold voltage degradation tn 0.25 Stress time exponent for interface trap inducing threshold voltage degradation tot0 0 First parameter for oxide trap inducing threshold voltage totdd 0 Drain voltage dependent coefficient for oxide electric field in threshold voltage degradation totde 1 Drain voltage exponent for oxide electric field in threshold voltage degradation totfd 636 Description 0 Oxide electric field dependent component for oxide trap inducing threshold voltage degradation HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 26: MOSFET Model Reliability Analysis (MOSRA) .MOSRA, .MOSRAPRINT, .MODEL, and .APPENDMODEL Commands Table 66 NBTI for PMOS Vth degradation (Continued) Parameter Default Description tottd 0 Temperature dependent component for oxide trap inducing threshold voltage degradation totwc 0 Channel width coefficient of oxide trap inducing threshold voltage degradation totwe 0 Channel width exponent of oxide trap inducing threshold voltage degradation totlc 0 Channel length coefficient of oxide trap inducing threshold voltage degradation totle 0 Channel length component of oxide trap inducing threshold voltage degradation tk 0.5 Stress time exponent for oxide trap inducing threshold voltage degradation tfd0 0 First parameter for transient degradation of threshold voltage tdcd 0 Duty cycle dependent exponent for transient degradation of threshold voltage HSPICE® User Guide: Simulation and Analysis B-2008.09 637 Chapter 26: MOSFET Model Reliability Analysis (MOSRA) .MOSRA, .MOSRAPRINT, .MODEL, and .APPENDMODEL Commands Mobility degradation Table 67 NBTI for PMOS Mobility degradation Parameter Default Description udcd Duty cycle dependent coefficient for transient mobility degradation uit0 0 First parameter for interface trap inducing mobility degradation uitce 0 Inversion charge exponent for interface trap inducing mobility degradation uitfd 0 Oxide electric field dependence for interface trap inducing mobility degradation uitlc 0 Channel length dependent coefficient for interface trap inducing mobility degradation uitle 0 Channel length exponent for interface trap inducing mobility degradation uittd 0 Temperature dependent coefficient of interface trap inducing mobility degradation uitwc 0 Channel width dependent coefficient for interface trap inducing mobility degradation uitwe 0 Channel width exponent for interface trap inducing mobility degradation uk 0.5 Stress time exponent for oxide trap inducing mobility degradation un 0.25 Stress time exponent for interface trap inducing mobility degradation uot0 0 First parameter for transient degradation uotdd 0 Drain voltage dependent coefficient for oxide electric field in mobility degradation uotde 1 Drain voltage exponent for oxide electric field in mobility degradation uotfd 638 0 0 Frequency exponent for transient degradation HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 26: MOSFET Model Reliability Analysis (MOSRA) .MOSRA, .MOSRAPRINT, .MODEL, and .APPENDMODEL Commands Table 67 NBTI for PMOS Mobility degradation (Continued) Parameter Default Description uotlc 0 Channel length coefficient for oxide trap inducing mobility degradation uotle 0 Channel length exponent for oxide trap inducing mobility degradation uottd 0 Duty cycle dependent exponent for transient degradation uotwc 0 Channel width coefficient for oxide trap inducing mobility degradation uotwe 0 Channel width exponent for oxide trap inducing mobility degradation utd0 0 First parameter transient mobility degradation HSPICE® User Guide: Simulation and Analysis B-2008.09 639 Chapter 26: MOSFET Model Reliability Analysis (MOSRA) .MOSRA, .MOSRAPRINT, .MODEL, and .APPENDMODEL Commands Synopsys LEVEL1 mosra model, HCI for NMOS and PMOS Table 68 HCI for NMOS and PMOS Parameter Default Description hiie 0 Saturation channel electric field for the impact ionization current hiii 0 First parameter for impact ionization hiil 0 Channel length dependent parameter for the impact ionization current hiit 0 Temperature dependent parameter for the impact ionization current hiivd0 0 First vds dependent parameter of the impact ionization current hiivd1 0 Second vds dependent parameter of the impact ionization current hiivd2 0 Third vds dependent parameter of the impact ionization current hiivg0 0 First vgs dependent parameter for the impact ionization current hiivg1 0 Second vgs dependent parameter for the impact ionization current hiivg2 0 Third vgs dependent parameter for the impact ionization current hiivgd 0 vds dependent parameter for the impact ionization current hk 0.5 Time exponent for mobility degradation induced by HCI hn 0.5 Time exponent for threshold voltage degradation induced by HCI Isubmode 1 Selection method for calculation of HCI degradation. ■ ■ 0: selects isub (substrate current) to calculate HCI degradation 1: selects Iii (impact ionization current) tdce Channel current exponent for threshold voltage degradation induced by HCI tdii 640 0 0 Impact ionization current exponent for threshold voltage degradation induced by HCI HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 26: MOSFET Model Reliability Analysis (MOSRA) .MOSRA, .MOSRAPRINT, .MODEL, and .APPENDMODEL Commands Table 68 HCI for NMOS and PMOS (Continued) Parameter Default Description tdle 0 Channel length exponent for threshold voltage degradation induced by HCI thci0 0 First parameter for threshold voltage degradation induced by HCI udce 0 Channel current exponent for mobility degradation induced by HCI udii 0 Impact ionization current exponent for mobility degradation induced by HCI udle 0 Channel length exponent for mobility degradation induced by HCI uhci0 0 First parameter for mobility degradation induced by HCI vdsat0 0 Nominal drain saturation voltage of the impact ionization current .APPENDMODEL This command appends the parameter values from the source model card (SrcModel) to the destination model card (DestModel). All arguments are required. Wildcards are supported for the .APPENDMODEL command. In addition, the .OPTION APPENDALL enables the top hierarchical level to use the .APPENDMODEL command even if the MOSFET model is embedded in a subcircuit. See .OPTION APPENDALL in the HSPICE Reference Manual: Commands and Control Options. Syntax .appendmodel SrcModel ModelKeyword1 DestModel ModelKeyword2 Argument Description SrcModel Source model name, e.g., the name of the MOSRA model. ModelKeyword1 Model type for SrcModel. For example, the keyword “mosra”. DestModel Destination model name, e.g., the original model in the model library. ModelKeyword2 Model type for DestModel. For example, 'nmos'. HSPICE® User Guide: Simulation and Analysis B-2008.09 641 Chapter 26: MOSFET Model Reliability Analysis (MOSRA) .MOSRA, .MOSRAPRINT, .MODEL, and .APPENDMODEL Commands Example This example appends the content of the model card hci_1 to the b3_nch BSIM3 model card. .appendmodel hci_1 mosra b3_nch nmos Wildcard Examples In this example, the mosra model p1_ra is appended to all of the pmos models. Note that you need quotation marks if the model name is defined only by a wildcard. .appendmodel p1_ra mosra “*” pmos In the following example, the mosra model p1_ra is appended to all of the pmos models that are named pch* (pch1, pch2, pch_tt, etc.). .appendmodel p1_ra mosra pch* pmos .OPTION APPENDALL With this option, .APPENDMODEL at the main (uppermost) circuit level hierarchy can be used even if the MOSFET model is embedded in a subcircuit. If there is .APPENDMODEL both in the main circuit and in a subcircuit, the .APPENDMODEL in the subcircuit will have higher priority. For example: .option appendall .appendmodel n_ra mosra nch nmos .SUBCKT mosra_test 1 2 3 4 M1 1 2 3 4 nch L=PL W=PW .model nch nmos level= ... .ENDS The .APPENDMODEL command in the main circuit will be used. .option appendall .appendmodel n_ra mosra nch nmos .SUBCKT mosra_test 1 2 3 4 M1 1 2 3 4 nch L=PL W=PW .model nch nmos level= ... .appendmodel n_ra1 mosra nch nmos .ENDS The .APPENDMODEL command in the subcircuit will be used. 642 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 26: MOSFET Model Reliability Analysis (MOSRA) .MOSRA, .MOSRAPRINT, .MODEL, and .APPENDMODEL Commands Simulation Output File For each post-stress circuit time point, HSPICE generates a set of reliability data containing the stress information for the selected transistors. HSPICE then back-annotates the degradations to these transistors (aged_device) and performs the post-stress simulation. For example: Degraded_device_parameter_Vth0 = Fresh_vth0 + delvth (NMOS) Degraded_device_parameter_Vth0 = Fresh_vth0 - delvth (PMOS) Degraded_device_paramter_U0 = Fresh_u0 * mulu0 HSPICE combines reliability data for all post-stress points in the following output *.radeg file. delvth0 mulu0 = 0.154229E-03 = 99.9985% ** \$DATA1 SOURCE='HSPICE' VERSION='A-2008.03-BETA3 32-BIT' ******Result of Reliability Analysis****** mosrasort: delvth0 Circuit time 0.100000E+05 mn1 Device Type: NMOS L= 0.100000E-06 W= 0.500000E-05 Bias Direction: forward delvth0 = 0.000000E+00 mulu0 = 100.0000% mulua = 100.0000% mulub = 100.0000% muluc = 100.0000% delnfactor= 0.000000E+00 mn2 Device Type: NMOS L= 0.100000E-06 W= 0.500000E-05 Bias Direction: forward delvth0 = 0.000000E+00 mulu0 = 100.0000% mulua = 100.0000% mulub = 100.0000% muluc = 100.0000% delnfactor= 0.000000E+00 HSPICE® User Guide: Simulation and Analysis B-2008.09 643 Chapter 26: MOSFET Model Reliability Analysis (MOSRA) Known Limitation mp2 Device Type: PMOS L= 0.100000E-06 W= 0.100000E-04 Bias Direction: forward delvth0 = 0.169531E-01 mulu0 = 100.0000% mulua = 100.0000% mulub = 100.0000% muluc = 100.0000% delnfactor= 0.000000E+00 mp1 Device Type: PMOS L= 0.100000E-06 W= 0.100000E-04 Bias Direction: forward delvth0 = 0.167418E-01 mulu0 = 100.0000% mulua = 100.0000% mulub = 100.0000% muluc = 100.0000% delnfactor= 0.000000E+00 RADEG Output Sorting (.OPTION MOSRASORT) HSPICE uses the option mosrasort to enable the descending sort for reliability degradation (RADEG) output. .option mosrasort=degradation_type_keyword The degradation type could be any degradation keyword in the RADEG output. For example, .option mosrasort=delvth0 HSPICE does a descending sort for RADEG output on delvth0’s value. If the mosrasort option is not specified, or the degradation type keyword is not recognized, HSPICE will not do the sorting. (Degradation type keywords are listed in the HSPICE Application Note: Unified Custom Reliability Modeling API (MOSRA API), available by contacting SPICE technical support.) If you only specify the option mosrasort, and do not specify the degradation type keyword, HSPICE sorts RADEG by the delvth0 keyword. HSPICE sorts the output separately in lists, one for NMOS, one for PMOS. HSPICE prints the NMOS list first, and then the PMOS list. Known Limitation HSPICE MOSRA currently does not work with Monte Carlo analysis. 644 HSPICE® User Guide: Simulation and Analysis B-2008.09 Part: 4 Simulation Applications This Part contains the following chapters/topics. ■ Chapter 27, Performing Digital Cell Characterization ■ Chapter 28, Behavioral Modeling ■ Chapter 29, Modeling Filters and Networks ■ Chapter 30, Simulation of Random Noise ■ Chapter 31, Using Verilog-A HSPICE® User Guide: Simulation and Analysis B-2008.09 645 646 HSPICE® User Guide: Simulation and Analysis B-2008.09 27 27 Performing Digital Cell Characterization Describes how to characterize cells in data-driven analysis. Also shows you some typical data sheet parameters. Most ASIC vendors use the basic capabilities of the .MEASURE statement in Synopsys HSPICE or HSPICE RF to characterize standard cell libraries, and to prepare data sheets. HSPICE or HSPICE RF stores input sweep parameters and measure output parameter, in measure output data files (design.mt0, design.sw0, and design.ac0). These files store multiple sweep data. You can use WaveView Analyzer to plot this data; for example, to generate fanout plots of delay versus load. You can also use the slope and intercept of the loading curves to calibrate VHDL, Verilog, Lsim, TimeMill, and Synopsys models.These topics are covered in the following sections: ■ Performing Basic Cell Measurements ■ Performing Advanced Cell Characterization ■ Cell Examples This chapter shows you some typical data sheet parameters. By looking at a series of typical data sheet examples, you can see the flexibility of the .MEASURE statement. This chapter also shows you how to characterize cells in data-driven analysis. Data-driven analysis automates cell characterization, including calculating the delay coefficient for the timing-simulator polynomial. You can simultaneously vary an unlimited number of parameters, or the number of analyses to perform. Cell characterization uses an ASCII file format for automated parameter input to HSPICE or HSPICE RF. HSPICE® User Guide: Simulation and Analysis B-2008.09 647 Chapter 27: Performing Digital Cell Characterization Performing Basic Cell Measurements Performing Basic Cell Measurements This section describes how to perform basic cell measurements. Rise, Fall, and Delay Calculations The following example does the following: ■ Uses the MAX function to calculate vmax, over the time region of interest. ■ Uses the MIN function to calculate vmin. ■ Uses the measured parameters in subsequent calculations, for accurate 10% and 90% points, when determining the rise and fall time. RISE=1 is relative to the time window that the TDval delay forms. ■ Uses a fixed value for the measure threshold, to calculate the Tdelay delay. .MEAS TRAN vmax MAX V(out) FROM=TDval TO=Tstop .MEAS TRAN vmin MIN V(out) FROM=TDval TO=Tstop .MEAS TRAN Trise TRIG V(out) val=’vmin+0.1*vmax’ + TD=TDval RISE=1 TARG V(out) val=’0.9*vmax’ RISE=1 .MEAS TRAN Tfall TRIG V(out) val=’0.9*vmax’ TD=TDval + FALL=2 TARG V(out) val=’vmin+0.1*vmax’ FALL=2 .MEAS TRAN Tdelay TRIG V(in) val=2.5 TD=TDval FALL=1 + TARG V(out) val=2.5 FALL=2 volts Trise 5v V(in) Tfall V(out) Tdelay TDval Tstop time Figure 116 Rise, Fall, and Delay Time Demonstration Ripple calculation performs the following: 648 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 27: Performing Digital Cell Characterization Performing Basic Cell Measurements ■ Delimits the wave at the 50% of VCC points ■ Finds the Tmid midpoint ■ Defines a bounded region by finding the pedestal voltage (Vmid) and then finding the first time that the signal crossed this value, Tfrom ■ Measures the ripple in the defined region using the peak-to-peak (PP) measure function from Tfrom to Tmid The following is an example: .MEAS .MEAS .MEAS .MEAS .MEAS .MEAS TRAN TRAN TRAN TRAN TRAN TRAN ripple defined region V(out) 5v Th1 WHEN V(out)=’0.5*vcc’ CROSS=1 Th2 WHEN V(out)=’0.5*vcc’ CROSS=2 Tmid PARAM=’(Th1+Th2)/2’ Vmid FIND V(out) AT=’Tmid’ Tfrom WHEN V(out)=’Vmid’ RISE=1 Ripple PP V(out) FROM=’Tfrom’ TO=’Tmid’ Vmid vcc 2.5 v 0v Th1Tfrom Tmid Th2 time Figure 117 Waveform to Demonstrate Ripple Calculation This file sweeps the sigma of the model parameter distribution, while it examines the delay. It shows you the delay derating curve, for the worst cases in the model. This example is based on demonstration netlist sigma.sp, which is available in directory \$<installdir>/demo/hspice/cchar. For a description of this technique for building a worst-case sigma library, see the HSPICE Simulation and Analysis User Guide. HSPICE® User Guide: Simulation and Analysis B-2008.09 649 Chapter 27: Performing Digital Cell Characterization Performing Basic Cell Measurements Figure 118 Inverter Pair Transfer Curves and Sigma Sweep vs. Delay 650 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 27: Performing Digital Cell Characterization Performing Basic Cell Measurements Delay versus Fanout The example sweeps the subcircuit multiplier to quickly generate five load curves. To obtain more accurate results, buffer the input source with one stage. For each second-sweep variable (m_delay and rms_power), the example calculates: ■ mean ■ variance ■ sigma ■ average deviance This example is based on the demonstration netlist load1.sp, which is available in directory \$<installdir>/demo/hspice/cchar. This example outputs the following results: meas_variable = m_delay mean = 273.8560p varian = 1.968e-20 sigma = 140.2711p avgdev = 106.5685p meas_variable = rms_power mean = 5.2544m varian = 8.7044u sigma = 2.9503m avgdev = 2.2945m Figure 119 Inverter Delay and Power, versus Fanout HSPICE® User Guide: Simulation and Analysis B-2008.09 651 Chapter 27: Performing Digital Cell Characterization Performing Basic Cell Measurements Pin Capacitance Measurement This example does the following: ■ Shows the effect of dynamic capacitance, at the switch point. ■ Sweeps the DC input voltage (pdcin) to the inverter. ■ Performs an AC analysis, at each 0.1 V increment. ■ Calculates the incap measure parameter from the imaginary current through the voltage source at 10 kHz in the AC curve (not shown). The peak capacitance (at the switch point) occurs when the voltage at the output side changes, in the direction opposite the input side of the Miller capacitor. This adds the Miller capacitance, times the inverter gain, to the effective capacitance. mp out in 1 1 mp w=10u l=3u mn out in 0 0 mn w=5u l=3u vin in 0 DC= pdcin AC 1 0 .ac lin 2 10k 100k sweep pdcin 0 5 .1 .measure ac incap find par( ’-1 * ii(vin)/ + (hertz*twopi)’ ) AT=10000hertz Figure 120 Graph of Pin Capacitance versus Inverter Input Voltage 652 HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 27: Performing Digital Cell Characterization Performing Basic Cell Measurements Op-amp Characterization of LM124 This example analyzes op-amps. This example uses: ■ .MEASURE statements to present a very complete data sheet. ■ Four .MEASURE statements, to reference the out0 output node of an opamp circuit. These statements use output variable operators for parameters: • decibels vdb(out0) • voltage magnitude vm(out0) • phase vp(out0) This example is based on the demonstration file alm124.sp, which is located in \$<installdir>/demo/apps. This example outputs the following results: unitfreq = 9.0786E+05 targ= 9.0786E+05 trig= 1.0000E+00 phasemargin = 6.6403E+01 gain(db) = 9.9663E+01 at= 1.0000E+00 from= 1.0000E+00 + to= 1.0000E+07 gain(mag)= 9.6192E+04 at= 1.0000E+00 from= 1.0000E+00 + to= 1.0000E+07 HSPICE® User Guide: Simulation and Analysis B-2008.09 653 Chapter 27: Performing Digital Cell Characterization Performing Advanced Cell Characterization Figure 121 Magnitude Plot of Op-Amp Gain Performing Advanced Cell Characterization This section provides example input files, which characterize cells for an inverter, based on 3-micron MOSFET technology. The program finds the propagation delay, and the rise and fall times, for the inverter, using best, worst, and typical cases for different fanouts. You can use this library data for digitalbased simulators, such as those used to simulate gate arrays and standard cells. The example is based on the demonstration file cellchar.sp, which is located in \$<installdir>/demo/hspice/apps. It demonstrates how to use the following to characterize a CMOS inverter: ■ ■ .DATA statement ■ AUTOSTOP option ■ SUBCKT definition ■ SUBCKT call ■ 654 .MEASURE statement models HSPICE® User Guide: Simulation and Analysis B-2008.09 Chapter 27: Performing Digital Cell Characterization Performing Advanced Cell Characterization 5.50 CELLCHAR.TRO V (2 5.0 V (3 4.50 4.0 Volt [Lin] 3.50 3.0 2.50 2.0 1.50 1.0 500.0M 0 0 10.0N Time [Lin] 20.0N 30.0N 35.255N Figure 122 Plotting the Simulation Outputs HSPICE® User Guide: Simulation and Analysis B-2008.09 655 Chapter 27: Performing Digital Cell Characterization Performing Advanced Cell Characterization 5.50 CELLCHAR.TRO V (2 5.0 V (3 4.50 4.0 Volt [Lin] 3.50 3.0 2.50 2.0 1.50 1.0 500.0M 0 0 10.0N Time [Lin] 20.0N 30.0N 35.255N Figure 123 Verifying the Measure Statement Results by the