Spectral Prediction for Specification-Based Loopback Test of Embedded Mixed-Signal Circuits

A traditional specification-based core-level test method is no longer attractive in testing deeply embedded analog and mixed-signal circuits due to limited accessibility and resource issues. In order to overcome such difficulties, loopback testing has been considered as a promising solution when circuits include data conversion units; however its widespread adoption has been hindered due to fault masking, which may cause serious yield loss and test escape. The combination of seriously degraded components in a signal path and overqualified components in another signal path, may result in the overall performance of the loopback path being completely fault-free. This paper presents an efficient loopback test methodology which provides test accuracy equivalent to a traditional specification-based test. In our approach, a traditional loopback scheme is re-configured with an analog filter and an adder implemented on a Device Interface Board (DIB), and a multiple tone input is applied to the DUTs. The outcome of the proposed test is a set of performance parameters, allowing the evaluation of DUTs with respect to its specification, and efficient guidance of a self-repair mechanism. The mathematical analysis for the fault masking problem, based on linearity and noise parameters, is provided. In addition, various design parameters which may impact the accuracy of the proposed method are investigated. Both simulation and hardware measurements are presented to validate the proposed technique.