A Discrete-Time Delta-Sigma Modulator with Low Power and High Resolution

This article presents a discrete-time third-order three-bit delta-sigma modulator (DSM) with the cascade-of- integrators feedforward (CIFF) topology, specifically designed for biological signal conversion in wearable medical devices. Within this modulator, a two-step adder is employed to facilitate the precise addition of analog signals while simultaneously mitigating the design requirements for the operational amplifier. To address the nonlinearity in multi-bit digital-to- analog converters (DACs), the data weighting averaging (DWA) digital calibration circuit is implemented. According to the post- simulation results, the modulator achieves a peak signal-to-noise and distortion ratio (SNDR) of 111.3 dB over a 1 kHz signal bandwidth, with a sampling frequency of 1.024 MHz. It operates with a power consumption of 0.52 mW from a 1.8 V supply, resulting in a Schreier figure of merit (FoM) of 174.1 dB.