Defining a BIST-oriented signature for mixed-signal devices

An original classification procedure for mixed-signal circuits testing is proposed which can be easily implemented in a Built-In-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 samples has been devised taking into account their sensitivities to the circuit performances to be checked for. The selected signature samples are analyzed on a sequential basis to cope with the requirements of a BIST hardware. For each sample an acceptance interval is adaptively calculated on the basis of the values assumed by the previous ones. A low resolution ADC can 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 have been used as test benches to assess the effectiveness of the proposed classification procedure. The total percentage of misclassification obtained is very small compared to other approaches proposed in literature for pseudorandom sequence based tests.