A Buffer and Splitter Insertion Framework for Adiabatic Quantum-Flux-Parametron Superconducting Circuits

Ruizhe Cai, Olivia Chen, Ao Ren, Ning Liu, Nobuyuki Yoshikawa, Yanzhi Wang

Abstract: Adiabatic Quantum-Flux-Parametron (AQFP) logic is an adiabatic superconductor logic that has been proposed as alternative to CMOS logic with extremely high energy efficiency. In AQFP technology, gates are driven by AC-power, which also serves as clock signal to synchronize the outputs of all gates in the same clock phase. As a matter of fact, AQFP circuits may require huge amount of buffers and splitters to be inserted to allow inputs to any gate having equal delay. Existing buffer and splitter insertion method does not deliver optimization, which could lead to huge space and delay overhead. A better automated buffer and splitter framework is imminent for more efficient AQFP circuits design. In this paper, we propose an automated buffer and splitter insertion method that is capable of adding optimized amount of buffers and splitters to any given gate-level netlist to achieve equal delay for all gates. The proposed method achieve equal delay by inserting buffers and splitters with any library limitation on the size of splitters. Experimental results suggest that the proposed method can deliver better results compared with the existing method, with up-to 40.84% less in size and 3.13% less in delay when splitter fan-out size is limited to four.