Current source modeling in the presence of body bias

Abstract

With the increasing use of adaptive body biases in high-performance designs, it has become necessary to build timing models that can include these effects. State-of-the-art timing tools use current source models (CSMs), which have proven to be fast and accurate. However, a straightforward extension of CSMs to incorporate multiple body biases results in unreasonably large characterization tables for each cell. We propose a new approach to compactly capture body bias effects within a mainstream CSM framework. Our approach features a table reduction method for compact storage, and a fast and novel waveform sensitivity method for timing evaluation. On a 45nm technology, we demonstrate high accuracy, with worst-case errors of under 5% in both slew and delay as compared to HSPICE. We show a speedup of over five orders of magnitude over HSPICE and almost 70x over conventional CSMs.