275 mA P584 mA 275 mA 10 V 859 mW static 7 Power 56 Leakage Control Leakage and

275 ma p584 ma 275 ma 10 v 859 mw static 7 power 56

This preview shows page 55 - 80 out of 90 pages.

  275 mA P 584 mA 275 mA 1.0 V 859 mW static
7: Power 56 Leakage Control Leakage and delay trade off Aim for low leakage in sleep and low delay in active mode To reduce leakage: Increase V t : multiple V t Use low V t only in critical circuits Increase V s : stack effect Input vector control in sleep Decrease V b Reverse body bias in sleep Or forward body bias in active mode
Capacitance Model for CMOS
Estimation of Interconnect Parasitics
The transmission-line effects have not been a serious concern in CMOS VLSI chips until recently, since the gate delays due to capacitive load components dominated the line delay in most cases. But as the fabrication technologies move to finer submicron design rules, the intrinsic gate delays tend to decrease significantly. Worst-case line length on a chip increases mainly due to increasing chip complexity, thus, the importance of interconnect delay increases in submicron technologies. In addition, as the widths of metal lines shrink, the transmission line effects and signal coupling between neighbouring lines become even more pronounced.
Which interconnections in a chip may cause serious problems in terms of delay? Each module contains a relatively large number of local connections between its functional blocks, logic gates, and transistors. So we have short distance intra- module connections. Fair amount of longer connections between the modules on a chip, the so-called inter-module connections ( MORE PROBLEMATIC)
Ex: Six interconnect lines running on 3 different levels
parallel-plate capacitance Cpp Fringing capacitance
The Lumped RC-Model, The Elmore Delay ( Elmore Delay = result *0.69)
Example: The Elmore Delay T i = C 1 R 1 + C 2 R 1 + C 3 (R 1 +R 3 ) + C 4 (R 1 +R 3 ) + C i (R 1 +R 3 +R i )

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture