# Timing Model Extraction for Sequential Circuits Considering Process Variations

## TL;DR

This paper presents a method to extract compact timing models for sequential circuits considering process variations, significantly speeding up statistical timing analysis while maintaining high accuracy.

## Contribution

It introduces a novel approach to extract smaller timing models for flip-flops and latches, enabling faster hierarchical timing analysis with minimal accuracy loss.

## Key findings

- Accelerates timing verification by orders of magnitude.
- Maintains less than 1% error in clock period estimation.
- Effective for hierarchical design with large circuits.

## Abstract

As semiconductor devices continue to scale down, process vari- ations become more relevant for circuit design. Facing such variations, statistical static timing analysis is introduced to model variations more accurately so that the pessimism in tra- ditional worst case timing analysis is reduced. Because all de- lays are modeled using correlated random variables, most statis- tical timing methods are much slower than corner based timing analysis. To speed up statistical timing analysis, we propose a method to extract timing models for flip-flop and latch based sequential circuits respectively. When such a circuit is used as a module in a hierarchical design, the timing model instead of the original circuit is used for timing analysis. The extracted timing models are much smaller than the original circuits. Ex- periments show that using extracted timing models accelerates timing verification by orders of magnitude compared to previ- ous approaches using flat netlists directly. Accuracy is main- tained, however, with the mean and standard deviation of the clock period both showing usually less than 1% error compared to Monte Carlo simulation on a number of benchmark circuits.