DELAY-FAULT COVERAGE ENHANCEMENT USING VARIABLE OBSERVATION TIMES

Detection of system timing failures has become a very important proble m whenever high speed system operation is required. It has been demons trated that delay fault coverage loss could be significant if improper propagation paths are used. This occurs when the delay test pair of a target propagation path cannot be effectively generated by an ATPG to ol, or when stuck-at test patterns are used as transition (or gate) de lay test patterns. In this work, an efficient method is proposed to re duce the amount of fault coverage loss by using variable observation t imes. The basic idea is to offset the shorter propagation paths (reall y used) by tightening the observation times. Given a probability distr ibution of defect sizes and a set of slack differences, this method is able to locate several observation times that result in small fault c overage loss.