Low-power scan testing and test data compression for system-on-a-chip

Test data volume and power consumption for scan vectors are two major problems in system-on-a-chip testing. Since static compaction of scan vectors invariably leads to higher power for scan testing, the conflicting goals of low-power scan testing and reduced test data volume appear to be irreconcilable. We tackle this problem by using test data compression to reduce both test data volume and scan power. In particular, we show that Golomb coding of precomputed test sets leads to significant savings in peak and average power, without requiring either a slower scan clock or blocking logic in the scan cells. We also improve upon prior work on Golomb coding by showing that a separate cyclical scan register is not necessary for pattern decompression. Experimental results for the larger ISCAS 89 benchmarks show that reduced test data volume and low power scan testing can indeed be achieved in all cases.