A Method for the Schmitt-Trigger Propagation-Delay Compensation in Asynchronous Sigma–Delta Modulator

This brief provides the mathematical analysis of the Schmitt-trigger propagation-delay influence on the asynchronous sigma-delta modulator (ASDM) output-signal frequency spectrum. Beside the propagation delay, the Schmitt-trigger slew-rate impact has been also presented. Based on the mathematical analysis, a method for the Schmitt-trigger propagation-delay compensation has been proposed. The method is implemented by introducing hysteresis-level modulation. The first-order ASDM simulation and measurement models have been proposed for the propagation-delay influence to the ASDM output-signal frequency and for the compensation method verification. The measurement and simulation results for the proposed method confirm the ASDM output frequency spectrum improvement.