Peak Capture Power Reduction for Compact Test Sets Using Opt-Justification-Fill

Excessive test power consumption is one of the obstacles which the chip industry currently faces. Peak capture power reduction typically leads to high pattern counts which increase test costs. This paper proposes a new methodology to reduce peak capture power during at-speed scan testing. In this method, a novel X-filling technique Opt-Justification-fill which uses optimization techniques to compute promising X-bits for low-power filling is proposed. This method is tightly integrated into a dynamic compaction flow to create silent test cubes with high compaction ability. By this, X-filling for fault detection and reducing switching activity is balanced. The proposed methodology can be applied during initial compact test set generation as well as a post-ATPG stage for a previously generated test set to reduce switching activity. Experiments show a significant reduction of peak capture power. At the same time, the pattern count increases only moderately which leads to reduced test costs.