Synthesis of SFQ Circuits with Compound Gates

Published in Conference on Very Large Scale Integration (VLSI-SoC), 2023

Rapid single-flux quantum (RSFQ) is one of the most advanced superconducting technologies with the potential to supplement or replace conventional VLSI systems. However, scaling RSFQ systems up to VLSI complexity is challenging due to fundamental differences between RSFQ and CMOS technologies. Due to the pulse-based nature of the technology, RSFQ systems require gate-level pipelining. Moreover, logic gates have an extremely limited driving capacity. Path balancing and clock distribution constitute a major overhead, often doubling the size of circuits. Gate compounding is a novel technique that substantially enriches the functionality realizable within a single clock cycle. In this paper, we propose a technology mapping method for RSFQ circuits that exploits compound gates. Our results show, on average, a 33% lower logic depth with 24% smaller area, as compared to the state of the art.

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