X-tolerant compression and application of scan-atpg patterns in a bist architecture

Scalable selector architecture for x-tolerant deterministic BIST

“…Finally, XDBIST relies on selective observation of unload values to achieve significant reduction in both test data and tester cycles [17]. XDBIST has full X-tolerance and ensures the same high test coverage and diagnosability as deterministic scan-ATPG (where all scan cells can be controlled and observed).…”

“…Test patterns are generated by a modified deterministic ATPG. Load values are compressed into PRPG seeds as part of test generation so that all care bits are set to the desired values [6], [17]. A small percentage of scan chains are selected to be unloaded during each pattern and the tester directly compares unloaded values.…”

“…To avoid adding cycles for initializing the PRPG, the PRPG-LFSR is coupled with a PRPG shadow that allows re-seeding with 0-cycle overhead [6]. A similar shadow is used to load the selector control bits [17], so no extra cycles are added. The tester views the DUT as a traditional scan-based design.…”

“…However, when compared to scan-ATPG, the design with XDBIST requires fewer shift cycles per load and can have fewer scan-in and scan-out pins (Figure 1), which significantly reduces test data and tester cycles. XDBIST patterns fit directly into a scan-test flow for failure diagnosis [17].…”

“…This paper introduces a new selector architecture that, when compared to the selector of [17], allows arbitrary compression ratios, scales to any number of scan chains, minimizes area overhead and reduces selector control data.…”