Logic synthesis for large pass transistor circuits

Abstract

Pass transistor logic (PTL) can be a promising alternative to static CMOS for deep sub-micron design. In this work, we motivate the need for CAD algorithms for PTL circuit design and propose decomposed BDDs as a suitable logic level representation for synthesis of PTL networks. Decomposed BDDs can represent large, arbitrary functions as a multi-stage circuit and can exploit the natural, efficient mapping of a BDD to PTL. A comprehensive synthesis flow based on decomposed BDDs is outlined for PTL design. We show that the proposed approach allows us to make logic-level optimizations similar to the traditional multi- level network based synthesis flow for static CMOS, and also makes possible optimizations with a direct impact on area, delay and power of the final circuit implementation which do not have any equivalent in the traditional approach. We also present a set of heuristical algorithms to synthesize PTL circuits optimized for area, delay and power which are key to the proposed synthesis flow. Experimental results on ISCAS benchmark circuits show that our technique yields PTL circuits with substantial improvements over static CMOS designs. In addition, to the best of our knowledge this is the first time PTL circuits have been synthesized for the entire ISCAS benchmark set.