Scan-Out Power Reduction for Logic BIST

Senling WANG  Yasuo SATO  Seiji KAJIHARA  Kohei MIYASE  

IEICE TRANSACTIONS on Information and Systems   Vol.E96-D   No.9   pp.2012-2020
Publication Date: 2013/09/01
Online ISSN: 1745-1361
DOI: 10.1587/transinf.E96.D.2012
Print ISSN: 0916-8532
Type of Manuscript: Special Section PAPER (Special Section on Dependable Computing)
low power,  BIST,  multi-cycle test,  shift power,  

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In this paper we propose a novel method to reduce power consumption during scan testing caused by test responses at scan-out operation for logic BIST. The proposed method overwrites some flip-flops (FFs) values before starting scan-shift so as to reduce the switching activity at scan-out operation. In order to relax the fault coverage loss caused by filling new FF values before observing the capture values at the FFs, the method employs multi-cycle scan test with partial observation. For deriving larger scan-out power reduction with less fault coverage loss and preventing hardware overhead increase, the FFs to be filled are selected in a predetermined ratio. For overwriting values, we prepare three value filling methods so as to achieve larger scan-out power reduction. Experiment for ITC99 benchmark circuits shows the effectiveness of the methods. Nearly 51% reduction of scan-out power and 57% reduction of peak scan-out power are achieved with little fault coverage loss for 20% FFs selection, while hardware overhead is little that only 0.05%.