Built in self test (BIST) for RSFQ circuits

In the era beyond the end of physical scaling of CMOS, growing attention is being paid to Superconducting electronics (SCE), especially Rapid Single Flux Quantum (RSFQ) logic due to its high-performance and low power consumption. In [1]–[3], static and delay fault models, corresponding automatic test pattern generator (ATPG) for testing these faults, and a scan architecture are developed. However, test pattern application involves moving patterns and responses via long wires from the test equipment at room temperature to the chip under test in liquid helium, which severely reduces the test clock frequency. At the same time, due to the high clock frequency of this technology, at-speed test is necessary for testing delay faults.In this paper, we present a scan-based BIST for RSFQ circuits which performs at-speed self-test including pseudo random pattern generation and response compression. We show that existing designs of pattern generators cannot be directly used for RSFQ and present new designs. Based on the scan architecture in [3], we design a new control strategy for at-speed self-test. We demonstrate that our new architecture supports testing at low overheads.