F. Novak et al., ENHANCING DESIGN-FOR-TEST FOR ACTIVE ANALOG FILTERS BY USING CLP(R), Analog integrated circuits and signal processing, 4(3), 1993, pp. 215-229
We describe a computer-aided approach to automatic fault isolation in
active analog filters which enhances the design-for-test (DFT) methodo
logy proposed by Soma (1990). His primary concern was in increased con
trollability and observability while the fault isolation procedure was
sketched only in general terms. We operationalize and extend the DFT
methodology by using CLP(R) to model analog circuits and by a model-ba
sed diagnosis approach to implement a diagnostic algorithm. CLP(R) is
a logic programming language which combines symbolic and numeric compu
tation. The diagnostic algorithm uses different DFT test modes and res
ults of voltage measurements for different frequencies and computes a
set of suspected components. Ranking of suspected components is based
on a measure of (normalized) standard deviations from predicted mean v
alues of component parameters. The diagnosis is performed incrementall
y, in each step reducing the set of potential candidates for the detec
ted fault. Case studies show encouraging results in isolation of soft
faults of a given low-pass biquad filter.