Scan-BIST based on cluster analysis and the encoding of repeating sequences

We present a built-in self-test (BIST) approach for full-scan designs that extracts the most frequently occurring sequences from deterministic test patterns. The extracted sequences are stored on-chip, and are used during test application. Three sets of test patterns are applied to the circuit under test during a BIST test session; these include pseudorandom patterns, semirandom patterns, and deterministic patterns. The semirandom patterns are generated based on the stored sequences and they are more likely to detect hard-to-detect faults than pseudorandom patterns. The deterministic patterns are encoded using either the stored sequences or the LFSR reseeding technique to reduce test data volume. We use the cluster analysis technique for sequence extraction to reduce the amount of data to be stored. Experimental results for the ISCAS-89 benchmark circuits show that the proposed approach often requires less on-chip storage and test data volume than other recent BIST methods.