Ternary Digital Output Data Link From SFQ Circuits

Abstract

Data transmission from single flux quantum (SFQ) circuits to room temperature electronics requires the use of superconductor output drivers and semiconductor amplifiers. The state-of-the-art superconductor output drivers such as SFQ-to-DC converter, superconducting quantum interference device (SQUID) stack, Suzuki stack (Josephson latching driver), and nanocryotron (nTron) have a binary output that produces either a logical 0’ or 1’. Due to the limited cooling power at 4 K, a higher data rate of superconductor output driver is desired to reduce the number of cryogenic cables (i.e., heat load) from 4 K to a higher temperature stage. In this paper, a novel ternary digital output data link is proposed by transmitting the data in three logical states such as 0’, 1’, and 2’. The proposed ternary data link consists of an encoder and a ternary superconductor output driver, which is based on a re-designed Suzuki stack circuit. As compared to a conventional (binary) output data link, the ternary data link can either increase the data rate by 50% or reduce the number of cryogenic cables by33%.