Fast test cost calculation for hybrid BIST in digital systems

The paper presents a hybrid BIST solution for testing systems-on-chip which combines pseudorandom test patterns with stored precomputed deterministic test patterns. A procedure is proposed for fast calculation of the cost of hybrid BIST at different lengths of pseudorandom test to find an optimal balance between test sets, and to perform a core test with minimum cost of both time and memory, and without losing test quality. Compared to the previous approach, based on iterative use of deterministic ATPG for evaluating the cost of stored patterns, a new, extremely fast procedure is proposed, which calculates costs on a basis of fault table manipulations. Experiments on the ISCAS benchmark circuits show that the new procedure is about two orders of magnitude faster than the previous one.