Abstract-The generation of significant power droop (PD) during at-speed test performed by Logic BIST is a serious concern for modern ICs. In fact, the PD originated during test may delay signal transitions of the circuit under test (CUT): an effect that may be erroneously recognized as delay faults, with consequent erroneous generation of test fails, and increase in yield loss. In this paper, we propose a novel, scalable approach to reduce the PD during at-speed test of sequential circuits with scan-based Logic BIST using the Launch-On-Capture scheme. This is achieved by reducing the activity factor of the CUT, by proper modification of the test vectors generated by the Logic BIST of sequential ICs. Our scalable solution allows us to reduce PD to a value similar to that occurring during the CUT in field operation, without increasing the number of test vectors required to achieve a target Fault Coverage (FC). We present a hardware implementation of our approach that requires limited area overhead. Finally, we show that, compared to recent alternative solutions providing a similar PD reduction, our approach enables a significant reduction of the number of test vectors (by more than 50%), thus the test time, to achieve a target FC.

Abstract-Significant peak power (PP), thus power droop (PD), during test is a serious concern for modern, complex ICs. In fact, the PD originated during the application of test vectors may produce a delay effect on the circuit under test signal transitions. This event may be erroneously recognized as presence of a delay fault, with consequent generation of an erroneous test fail, thus increasing yield loss. Several solutions have been proposed in the literature to reduce the PD during test of combinational ICs, while fewer approaches exist for sequential ICs. In this paper, we propose a novel approach to reduce peak power/power droop during test of sequential circuits with scanbased Logic BIST. In particular, our approach reduces the switching activity of the scan chains between following capture cycles. This is achieved by an original generation and arrangement of test vectors. The proposed approach presents a very low impact on fault coverage and test time, while requiring a very low cost in terms of area overhead.