A New Algorithm for Simultaneous Gate Sizing and Threshold Voltage Assignment

Abstract

Gate sizing and threshold voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> ) assignment are popular techniques for circuit timing and power optimization. Existing methods, by and large, are either sensitivity-driven heuristics or based on discretizing continuous optimization solutions. Sensitivity-driven heuristics are easily trapped in local optima and the discretization may be subject to remarkable errors. In this paper, we propose a systematic combinatorial approach for simultaneous gate sizing and V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> assignment. The core idea of this approach is joint relaxation and restriction, which employs consistency relaxation and coupled bi-directional solution search. The process of joint relaxation and restriction is conducted iteratively to systematically improve solutions. Our algorithm is compared with a state-of-the-art previous work on benchmark circuits. The results from our algorithm can lead to about 22% less power dissipation subject to the same timing constraints.