An accurate and efficient gate level delay calculator for MOS circuits

Abstract

The authors describe an accurate and efficient gate-level delay calculator that automatically characterizes and computes the gate delays of MOS circuits. The high accuracy is attributed to a sophisticated delay model, which includes an accurate representation of the waveform, a consistent and meaningful definition of delay, a consideration of waveform slope effects at both the input and output of a gate, and an innovative approach for handling transmission gate circuits. The highly efficient delay characterization is accomplished through a fast timing simulation technique, a theorem that reduces a two-dimensional delay table into a scaled one-dimensional table, and an incremental characterization process. The delay calculator has been used in a production timing analyzer and a production multiple delay simulator since 1986. The multiple delay simulator performs 5000 times faster than a SPICE-like circuit simulator at only 15% cost of accuracy. Gate delay models, delay characterization, and practical examples are presented.<>