iFill: An Impact-Oriented X-Filling Method for Shift- and Capture-Power Reduction in At-Speed Scan-Based Testing

In scan-based tests, power consumptions in both shift and capture phases may be significantly higher than that in normal mode, which threatens circuits´ reliability during manufacturing test. In this paper, by analyzing the impact of X-bits on circuit switching activities, we present an X-filling technique that can decrease both shift- and capture-power to guarantees the reliability of scan tests, called iFill. Moreover, different from prior work on X-filling for shift-power reduction which can only reduce shift-in power, iFill is able to decrease power consumptions during both shift-in and shift-out. Experimental results on ISCAS´89 benchmark circuits show the effectiveness of the proposed technique.