Scan shift operations cause many gates to switch simultaneously. As a result, excessive IR-drop may occur, disrupting the states of some scan flip-flops and thus corrupting test stimuli or test responses. A widely-adopted approach to solving this problem is to design multiple scan chains and shift only a group of them at a time. This paper presents a novel scan chain grouping algorithm for reducing the probability of test data corruption caused by excessive instantaneous IR-drop on scan flip-flops. Experimental results show significant improvement of shift-power safety on all large ITC' 99 benchmark circuits.
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