Testing Biquad Filters under Parametric Shifts Using X-Y Zoning

Testing mixed-signal circuits is a difficult task due to defect modelling challenges, observability and controllability restrictions and ATE bandwidth limitations. In previous works, X-Y Zoning method has been proposed as a BIST technique for mixedsignal and analogue circuits. Some experiments showed its viability in detecting parametric deviations in analog cells. . In this paper the optimal X-Y test of a Biquad filter is addressed in terms of selecting the optimal frequency of the excitation and the best partition of the X-Y plane to obtain the best sensitivity of the BIST scheme to parametric shifts of the parameters defining the filter. The study has been particularized to shifts in the natural frequency ω0 of the Biquad filter. Analytical results on the best input as well as the best partition of the observed X-Y Lissajous plots are obtained. Extensive MATLAB simulations validate the proposal which has been also validated experimentally. For these experiments, multiple implementations of the Biquad with nominal and shifted parameters have been implemented using a commercial Field Programmable Analog Array (FPAA). The experimental measures show good correlation with the analytical expressions and the simulations performed.