Performance computation for precharacterized CMOS gates with RC loads

Abstract

For efficiency, the performance of digital CMOS gates is often expressed in terms of empirical models. Both delay and short-circuit power dissipation are sometimes characterized as a function of load capacitance and input signal transition time. However, gate loads can no longer be modeled by purely capacitive loads for high performance CMOS due to the RC metal interconnect effects. This paper presents a methodology for interfacing empirical gate models to reduced order RC interconnect models in terms of a nonlinear iteration procedure. The delay and power are calculated with errors on the same order as those for the original empirical equations. Moreover, a linear equivalent gate model is generated which accurately captures the delays at the interconnect fan-out nodes.