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Test data modification based on test relaxation and X-filling is the preferable approach for reducing excessive IR-drop in at-speed scan testing to avoid test-induced yield loss. However, none of the existing test relaxation methods can control the distribution of identified donpsilat care bits (X-bits), thus adversely affecting the effectiveness of IR-drop reduction. In this paper, we propose a novel test relaxation method, called Distribution-Controlling X-Identification (DC-XID), which controls the distribution of X-bits identified from a set of fully-specified test vectors for the purpose of effectively reducing IR-drop. Experimental results on large industrial circuits demonstrate the effectiveness and practicality of the proposed method in reducing IR-drop, without any impact on fault coverage, test data volume, or test circuit size.
Date of Conference: 10-13 Nov. 2008