Scan Architecture With Mutually Exclusive Scan Segment Activation for Shift- and Capture-Power Reduction

Abstract

Power dissipation during scan testing is becoming an important concern as design sizes and gate densities increase. While several approaches have been recently proposed for reducing power dissipation during the shift cycle (minimum-transition don't care fill, special scan cells, and scan chain partitioning), limited work has been carried out toward reducing the peak power during test response capture and the few existing approaches for reducing capture power rely on complex automatic test pattern generation (ATPG) algorithms. This paper proposes a scan architecture with mutually exclusive scan segment activation which overcomes the shortcomings of previous approaches. The proposed architecture achieves both shift and capture-power reduction with no impact on the performance of the design, and with minimal impact on area and testing time (typically 2%-3%). An algorithmic procedure for assigning flip-flops to scan segments enables reuse of test patterns generated by standard ATPG tools. An implementation of the proposed method had been integrated into an automated design flow using commercial synthesis and simulation tools which was used on a wide range of benchmark designs. Reductions up to 57% in average power, and up to 44% and 34% in peak-power dissipation during shift and capture cycles, respectively, were obtained when using two scan segments. Increasing the number of scan segments to six leads to reductions of 96% and 80% in average power and, respectively, maximum number of simultaneous transitions.