Defining a bist-oriented signature for mixed-signal devices

An originai classification procedure for mixed--signal circuits testing is proposed which can be easily implemented in a Built-Jn-Self-Test (BIST) environment. A signature for the device under test (DUT) is defined in the space of the input-output cross-correlation samples and is evaluated so as to minimize the misclassification error. In particular, a suitable strategy for the choice of these sarnples has been devised taking into account their sensitivities to the circuii performances to be checked for. The selected signature sarnples are analyzed on a sequential basis to cope with the requirernents of a BIST hardware. For each sarnple an acceptance interval is adaptively calculated on the basis of the values assumed by the previous ones. A low resolution ADC ean be employed to process the DUT output, thus making possible the application of the testing technique to relatively high speed circuits. A fourth order Butterworth and a third order Chebyshev low-pass filters bave been used as test benches to assess the effectiveness of the proposed classification procedure. The total percentage of misclassification obtained is very small cotnpared to other approaches proposed in literature for pseudorandom sequence based tests.