Spectral prediction for specification-based loopback test of embedded mixed-signal circuits

Loopback testing of mixed-signal SOCs provides a low-cost test solution, but suffers from fault masking, resulting in serious yield loss and low test accuracy. This paper presents an efficient loopback test methodology which enables individual characterization of dynamic performance of devices under test (DUTs) in loopback mode. DUTs are loop-backed externally on a loadboard (DUT board), and a simple filter and an analog adder on the loadboard produce a composite loopback response. Characteristic parameters are extracted from these loopback responses, and a non-linear regression technique based on spectral predictors is used to predict various performance parameters such as Gain, SNR, THD and SINAD. The spectral predictor provides more accurate and reliable prediction compared to a time-domain approach. Both simulation and hardware measurements are presented to validate the proposed technique.