A Fixed-Pulse Shape Feedback Technique with reduced clock-jitter sensitivity in Continuous-Time sigma-delta modulators

A novel fixed-Pulse Shape (PS) clock-jitter insensitive Return-to-Zero (RZ) feedback technique in CT ΣΔ modulators is presented. This technique offers a method to reduce the clock-jitter effect in feedback DAC. A switched-RC network and a zero-crossing detector are applied to generate jitter insensitive feedback pulse. This technique was verified in a designed 2^nd order CT ΣΔ modulator. A stable 64dB SNDR was obtained with the clock-jitter effect of 2% of a clock cycle. Simulation results show that using the proposed technique, an SNDR improvement up to 30dB can be achieved comparing with traditional RZ DAC.