Using Launch-on-Capture for Testing Scan Designs Containing Synchronous and Asynchronous Clock Domains

This paper presents a hybrid automatic test pattern generation (ATPG) technique using the staggered launch-on capture (LOC) scheme followed by the one-hot LOC scheme for testing delay faults in a scan design containing asynchronous clock domains. Typically, the staggered scheme produces small test sets but needs long ATPG runtime, whereas the one-hot scheme takes short ATPG runtime but yields large test sets. The proposed hybrid technique is intended to reduce test pattern count with acceptable ATPG runtime for multi-million-gate scan designs. In case the scan design contains multiple synchronous clock domains, each group of synchronous clock domains is treated as a clock group and tested using a launch aligned or a capture aligned LOC scheme. By combining these schemes together, we found the pattern counts for two large industrial designs were reduced by approximately 1.1X to 2.1X, while the ATPG runtime was increased by 10% to 50%, when compared to the one-hot clocking scheme alone.