Low Power Test-Compression for High Test-Quality and Low Test-Data Volume

Test data decompressors targeting low power scan testing introduce significant amount of correlation in the test data and thus they tend to adversely affect the coverage of unmodeled defects. In addition, low power decompression needs additional control data which increase the overall volume of test data to be encoded and inevitably increase the volume of compressed test data. In this paper we show that both these deficiencies can be efficiently tackled by a novel pseudorandom scheme and a novel encoding method. The proposed scheme can be combined with existing low power decompressors to increase unmodeled defect coverage and almost totally eliminate control data. Extensive experiments using ISCAS and IWLS benchmark circuits show the effectiveness of the proposed method when it is combined with state-of-the-art decompressors.