DESIGN OF COMPACTORS FOR SIGNATURE-ANALYZERS IN BUILT-IN SELF-TEST

  • Authors:
  • Peter Wohl;John A. Waicukauski;T. W. Williams

  • Affiliations:
  • -;-;-

  • Venue:
  • ITC '01 Proceedings of the 2001 IEEE International Test Conference
  • Year:
  • 2001

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Abstract

Originally developed decades ago, logic built-in self-test(BIST) evolved and is now increasingly being adopted tocope with rapid growth in design size and complexity. Comparedto deterministic pattern test, logic BIST requiresmany more test patterns, and therefore, increased test timeunless many more internal scan chains can be shifted in parallel.To match this large number of scan chains, the widthof the signature analyzer would have to be enlarged, whichwould result in large area overhead and signature storagespace. Instead, a combinational space-compactor isinserted between the scan chain outputs and the signatureanalyzer inputs. However, the compactor may deterioratethe ability to test and diagnose the design. This paper analyzeshow compactors affect test and diagnosis and showsthat compactors can be designed to actually improve thetestability of certain faults, while providing full diagnosiscapability. Algorithms that allow automated design of optimalcompactors are presented and results are discussed.