Pseudo-random testing and signature analysis for mixed-signal circuits

In this paper, we address the problem of functional testing of mixed-signal circuits using pseudo-random patterns. By embedding the linear, time-invariant (LTI) analog circuit between a digital-to-analog converter (DAC) and an analog-to-digital converter (ADC), we can model the analog and converter circuitry as a digital LTI system and test it using the pseudo-random vectors. We give mathematical analysis and formulate the pseudo-random testing process as the linear transformation of a random process by the analog LTI device under test (DUT). We choose the first and the second moments of the transformed random process, which are closely related to the functionality of the DUT, as the signatures for fault detection. We show that such signatures can be estimated by proper arithmetic operations on the output responses of the DUT to the vectors generated by LFSRs. We illustrate and compare the effectiveness of several possible choices of signatures through analysis and experimental results of several circuits, in terms of their fault detection capabilities and the testing hardware requirements.