Design of multiple fanout clock distribution network for rapid single flux quantum technology

Abstract

Rapid Single Flux Quantum (RSFQ) logic cells have traditionally been limited to driving one fanout cell because of the difficulty in distributing the single flux quantum pulse to multiple fanouts. This paper presents a method to modify the standard RSFQ cells at their input/output interfaces to other cells in order to support a multiple-fanout drive capability. This capability is especially useful for clock distribution in RSFQ logic. This is because RSFQ logic is requires the clock signal to be provided to every logic gate. This is why this paper focuses on the clock signal driving more than one cell without the use of splitters. The potential tradeoff is in lower margins for the cells. However, by careful design of the RSFQ cells, the yield is not compromised by our proposed technique.