Noise Analysis of Continuous-Time ΣΔ Modulators with Switched-Capacitor Feedback DAC

This paper discusses the calculation of the input referred noise contribution of a switched-capacitor (SC feedback DAC to a continuous-time (CT) sigma-delta (SigmaDelta) modulator. Such a hybrid CT/SC modulator combines the high speed and implicit anti-aliasing filter of a CT loop filter with the greater jitter immunity of a SC DAC. A simple expression for the total input referred circuit noise for this type of SigmaDelta modulator is derived