Bounding integrator output of sigma-delta modulator by time delay feedback control

Abstract

Internal integrator saturation is one of the practical problems arising in second- and high-order sigma-delta modulators (SDMs). It has been avoided by scaling integrator gains, feedback coefficients and other circuit parameters. In the paper, a novel compensation technique has been introduced to keep the signal levels throughout the modulator below saturation limits most of the time. The technique is based on feedback compensation and contains a delay element and a feedback gain and is employed to sigma-delta modulators by use of the unquantised output signal alone. The technique can readily be applied to various configurations of oversampling converters, single-loop and multiple-loop structures, and improves their stability.