A continuous-time ΔΣ modulator with 87 dB dynamic range in a 2MHz signal bandwidth using a Switched-Capacitor Return-to-Zero DAC

Abstract

We introduce the Switched-Capacitor Return-to-Zero (SCRZ) DAC, which combines the low clock jitter sensitivity of a Switched-Capacitor DAC with the low distortion of a Return-to-Zero DAC. A single-bit continuous-time ΔΣ modulator that uses the SCRZ technique and opamp-assistance to improve DAC linearity and reduce jitter sensitivity achieves 87.1/84.5/82.3 dB DR/SNR/SNDR in a 2 MHz bandwidth. Operating at a sampling rate of 256 MHz in a 0.18 μm CMOS process, the CTDSM dissipates 16.5 mW from a 1.8 V supply.