Accurate fault detection in switched-capacitor filters using structurally allpass building blocks

A methodology for testing switched-capacitor filters implemented by the parallel connection of structurally allpass sections is presented. The proposed approach enables multiple fault detection and accurate estimation of the actually implemented parameter values. The technique is applied to a lowpass fifth-order elliptic filter designed on a standard double-poly, double-metal 0.8 μm CMOS technology, satisfying typical specifications for video communication applications. In this case the relative area needed for testing is only 8% of the total filter area, and it decreases as the filter order increases.