Balanced Factorization and Rewriting Algorithms for Synthesizing Single Flux Quantum Logic Circuits

Abstract

Single Flux Quantum (SFQ) logic with switching energy of 100zJ1 and switching delay of 1ps is a promising post-CMOS candidate. Logic synthesis of these magnetic-pulse-based circuits is a very important step in their design flow with a big impact on the total area, power consumption, and critical path delay. SFQ circuits has some properties different from CMOS which should be taken into consideration in the design and implementation flow of these circuits. One of these properties is requirement of path balancing in the standard SFQ circuit design. Standard CMOS-based rewriting and factorization algorithms fail to preserve the balancing property of SFQ circuits. Therefore, they end up generating circuits with huge path balancing overheads. Our proposed balanced factorization and rewriting algorithms are designed specifically to solve this problem. Experimental results show that a combination of balanced factorization and rewriting algorithms reduces the path balancing overhead by an average of 63% for 15 benchmark circuits, and area by up to 23% compared to state-of-the-art logic synthesis tools.