voltage regulator altera - White Paper Voltage Regulator...

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White Paper Voltage Regulator Selection for FPGAs November 2008, ver. 1.0 1 WP-01071-1.0 Introduction As FPGAs increase in sophistication to provide additional features such as phase-locked loops (PLLs), memory interfaces, and transceiver functionality, the power requirements and designs for FPGAs are becoming more challenging. These include multiple power rails for specialty blocks and circuitry, multiple voltage levels, and increased current requirements. This paper discusses how to identify the various rails associated with Altera ® devices, analyze the power requirements, and select the appropriate voltage regulator modules, then walks through a design example for a Stratix ® IV FPGA. FPGA Voltage Rails As a first step in determining regulator selection, all of the voltage rails that the FPGA needs must be identified. These voltages are available via a pin list (commonly provided by the FPGA vendor), which identifies every power pin, provides definitions of each type, and specifies the required voltage levels. Figure 1 shows a sample pin list for a Stratix IV GX device. Figure 1. Stratix IV GX Pin Table Excerpt This example only identifies a few of the FPGA voltage rails. There are a number of different voltages an FPGA may need to operate, including: Core voltage, at which the internal logic array operates I/O voltages, which drive the I/O buffers. The I/O pins can support a range of voltages. The I/Os are grouped in banks, each of which can operate at a different voltage. I/O reference voltages are generated from the I/O voltage. PLL voltages, which power the analog and digital circuitry for the PLLs located in the core Transceiver voltages, which power the digital and analog circuitry of the transceiver, receiver, and transmitter paths, and transceiver I/O buffers Voltage Rail Requirements There are various parameters to take into consideration when selecting a voltage regulator. The current consumption requirement is the most important and should be considered first, followed by shared and isolated voltage rails, then regulator accuracy and ripple specifications.
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Voltage Regulator Selection for FPGAs Altera Corporation 2 Current Consumption Before a regulator can be selected, the total current requirement must be known for that voltage rail. In an FPGA, a power calculator can be used to estimate the current draw of a specific voltage rail as well as for all voltage rails. Altera provides the customer with an Early Power Estimator (EPE), shown in Figure 2 , for many of its devices. Each power rail of the FPGA can be calculated from this estimator. Add the current values of the shared rails to estimate the total current for that particular rail. Figure 2. Stratix IV GX EPE—Main Page
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voltage regulator altera - White Paper Voltage Regulator...

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