Power-Efficient Gm-C DSMs With High Immunity to Aliasing, Clock Jitter, and ISI

Abstract

Recent progress in continuous-time (CT) Delta-Sigma modulators (DSMs) research has shown that applying a passive RC low-pass filter (LPF) in the feedback path can significantly improve the power efficiency of a CT DSM. On the other hand, to achieve high performance, a CT DSM faces the adverse effects of clock jitter, intersymbol interference (ISI), or degradation of antialiasing ability. These challenges are extremely difficult to tackle simultaneously without consuming excessive power. This paper proposes a Gm-C DSM with a combined RC and switched-capacitor LPF frontend stage to achieve a high performance against aliasing, clock jitter, and ISI simultaneously while having an extremely low power consumption. Transistor-level simulations on an audio band modulator and a 10-MHz bandwidth modulator are given, verifying the high immunity of the proposed circuit to clock jitter, ISI, and aliasing while attaining a power efficiency up to 7.4 fJ/conversion step.