Dynamic scan clock control for test time reduction maintaining peak power limit

We dynamically monitor per cycle scan activity to speed up the scan clock for low activity cycles without exceeding the specified peak power budget. The activity monitor is implemented either as on-chip hardware or through pre-simulated and stored test data. In either case a handshake protocol controls the rate of test data flow between the automatic test equipment (ATE) and device under test (DUT). The test time reduction accomplished depends upon an average activity factor α. For low α, about 50% test time reduction is analytically shown. With moderate activity, α = 0.5, simulated test data gives about 25% test time reduction for ITC02 benchmarks. For full scan s38584, the dynamic scan clock control reduced the test time by 19% when fully specified ATPG vectors were used and by 43% for vectors with don´t cares. BIST with dynamic clock showed about 19% test time reduction for the largest ISCAS89 circuits in which the hardware activity monitor and scan clock control required about 2-3% hardware overhead.