Defect-oriented test methodology for complex mixed-signal circuits

Testing of analog blocks in digital circuits is emerging as a critical factor in the success of mixed-signal ICs. The present specification-oriented testing of these blocks results in high test costs and doesn´t ensure detection of all defects, causing potential reliability problems. To solve these problems, in this paper a defect-oriented test methodology for mixed analog-digital circuits is proposed. The strength of the method is demonstrated by an implementation for a complex mixed-signal circuit, a flash analog-to-digital converter. It is shown that with simple tests 93% of the defects in this circuit can be detected. Moreover application of DfT guidelines derived from this test methodology may improve the defect coverage to 99%. First impressions lead to the conclusion that the analyzed test obtains a higher defect coverage with lower test costs than functional tests