Efficient test-point selection for scan-based BIST

摘要

We propose a test point selection algorithm for scan-basednbuilt-in self-test (BIST). Under a pseudorandom BIST scheme, thenobjectives are (1) achieving a high random pattern fault coverage, (2)nreducing the computational complexity, and (3) minimizing thenperformance as well as the area overheads due to the insertion of testnpoints. The proposed algorithm uses a hybrid approach to accuratelynestimate the profit of the global random testability of a test pointncandidate. The timing information is fully integrated into the algorithmnto access the performance impact of a test point. In addition, ansymbolic procedure is proposed to compute testability measures morenefficiently for circuits with feedbacks so that the test point selectionnalgorithm can be applied to partial-scan circuits. The experimentalnresults show the proposed algorithm achieves higher fault coverages thannprevious approaches,with a significant reduction of computationalncomplexity. By taking timing information into consideration, thenperformance degradation can he minimized with possibly more test points