A Low Power Built-in Self-Test Scheme Based on Overlapping Bit Swapping Linear Feedback Shift Register

In order to reduce test power, a low-transition test pattern generator (TPG) using linear feedback shift register (LFSR), called overlapping bit swapping LFSR(OBS-LFSR), has been presented. The proposed OBS-LFSR is composed of an LFSR, a 2 × 1 multiplexer and a detection module. The proposed OBS-LFSR swaps the last two cells when a detection module detects the state of three successive cells in being 101/010. In this way, the swapped patterns are inserted between the random patterns, and the random nature of the test patterns is kept intact. The goal of inserting swapped patterns is to reduce the transitional activities in primary inputs, which in turn reduces the switching activities inside the circuit under test (CUT). The hardware overhead of the additional circuit logic to the LFSR is negligible compared to the large CUT. The experimental results indicate that the proposed OBS-LFSR achieves up to 11.94% and 17.31% reduction in average and peak power with a little hardware overhead and without compromising the fault coverage compared with the previous scheme.