A Delay Metric for RC Circuits Based on the Weibull Distribution

Abstract

Physical synthesis optimizations require fast and accurate analysis of RC networks. Elmore first proposed matching circuit moments to a probability density function (PDF), which led to widespread adoption of his simple and fast metric. The more recently proposed PRIMO and H-gamma metrics match the circuit moments to the PDF of a Gamma statistical distribution. We instead propose to match the circuit moments to a Weibull distribution and derive a new delay metric called Weibull-based delay (WED). The primary advantages of WED over PRIMO and H-gamma are its efficiency and ease of implementation. Experiments show that WED is robust and has satisfactory accuracy at both near- and far-end nodes.