Novel approach to reduce power droop during scan-based logic BIST

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 scan-based Logic GIST. 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.