Application of Sequential Test Set Compaction to LFSR Reseeding

LFSR reseeding techniques are often applied in BIST due to their ability to considerably improve the fault coverage and test application time by embedding specific vectors into the pseudorandom sequence. The efficiency of a typical reseeding scheme to a large extent depends on the seed selection and consequent test sequence optimization algorithms. This paper proposes a novel efficient reseeding optimization algorithm that is based on test compaction techniques for sequential designs. The proposed approach relies on the branch-and-bound search technique, which can provide the optimal test set compaction solution for a given test setup. Alternatively, it can run for a limited time in a heuristic mode, producing intermediate results. Experiments show that applied heuristics can yield optimal or quasi-optimal solutions in polynomial time. These solutions outperform previously published reseeding and hybrid BIST results.