An almost full-scan BIST solution-higher fault coverage and shorter test application time

  • Authors:
  • Huan-Chih Tsai;Sudipta Bhawmik;Kwang-Ting Cheng

  • Affiliations:
  • -;-;-

  • Venue:
  • ITC '98 Proceedings of the 1998 IEEE International Test Conference
  • Year:
  • 1998

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Abstract

This paper illustrates that for existing scan-based Built-InSelf-Test (BIST) architectures under the pseudo-randomtesting scheme, scanning all flip-flops may not be the beststrategy for achieving high fault coverage with a practicallimit on test length. In general, for scan-based BIST, notscanning flip-flops with relatively high pseudo-random observabilitiesthrough the primary outputs may indeed improvethe fault coverage as well as the test application time.We illustrate the issues and present a flip-flop selection strategyfor scan-based BIST to maximize the fault coverageand reduce the test application time. Experiments havebeen conducted based on an industrial tool psb2 for severalbenchmark circuits. The results show that the almost-full-scancircuits based on our flip-flop selection strategy canachieve higher fault coverages and significantly shorter testapplication time as compared with the full-scan circuits.