Improving Transition Delay Test Using a Hybrid Method

The transition-fault-testing technique combines the launch-off-shift method and an enhanced launch-off-capture method for scan-based designs. The technique improves fault coverage and reduces pattern count and scan-enable design effort. It is practice oriented, suitable for low-cost testers, and implementable with commercial ATPG tools. Scan-based structural tests increasingly serve as a cost- effective alternative to the at-speed functional-pattern approach to transition delay testing. The proposed hybrid technique significantly reduces the design effort and eases the timing closure by selecting a small subset of scan chains to be controlled using LOS. The experimental results also show that the pattern count is reduced and fault coverage is considerably increased. A statistical analysis is required to find the optimum number of LOS-controlled scan chains. Minimizing the number of LOS-controlled scan chains will even further reduces the design effort, and future work must focus on this issue