Quality metrics for mixed-signal indirect testing

Analog and mixed-signal circuit testing is a challenging task demanding large amounts of resources. In order to battle against this drawback, alternate testing has been established as an efficient way of testing analog and M-S circuits by using indirect measures instead of the classic specification based testing. In this work we propose the use of Kendall´s Tau rank correlation coefficient for rating the suitability of a set of candidate indirect measures to be used in mixed-signal testing. Such criterion is shown to be adequate since it allows to avoid or minimize information redundancy in the measures set. As a proof of concept, a 4th order band-pass Butterworth filter has been simulated under the presence of process variations. The circuit has been tested using a subset of measures selected according to minimum Kendall´s Tau coefficient. Analog test efficiency metrics are reported showing test misclassification rate is among the best 15% possible, therefore validating the proposal.