Scan Chain Grouping for Mitigating IR-Drop-Induced Test Data Corruption

Loading and unloading test patterns during scan testing causes many scan flip-flops to trigger simultaneously. This instantaneous switching activity during shift in turn may cause excessive IR-drop that can disrupt the states of some scan flip-flops and corrupt test stimuli or responses. A common design technique to even out these instantaneous power surges is to design multiple scan chains and shift only a group of the scan chains at a same time. This paper introduces a novel algorithm to optimally group scan chains so as to minimize the probability of test data corruption caused by excessive instantaneous IR-drop on scan flip-flops. The experiments show optimal results on all large ITC'99 benchmark circuits.