Robust data compression for analogue test outputs

Ohletz [1991] described a mixed signal circuit architecture which can be reconfigured to allow built-in-self-test of both analogue and digital parts. In testing the analogue section an on board test signal can be generated from digital components, the analogue test output fed through an A-D converter and the resulting digital bit stream used as the input to a digital signature analyser. Clearly such a test strategy has a number of advantages, but particular issues arise in using signature analysis in this way due to the tolerance bands associated with analogue signals. Such tolerances complicate the process of A-D conversion and lead to possible differences in the bit stream between two good devices with the danger of classifying good devices as faulty. The paper describes and evaluates a method for overcoming this problem by illustrating it with a number of circuits.