A Low-Power 68.4 dB Signal-to-Noise-and-Distortion Ratio Noise-Shaping SAR ADC for Biomedical Applications

This paper introduces a novel analog-to-digital converter (ADC) employing a passive noise-shaping (NS) technique combined with a chopper-stabilized comparator, enhancing performance and reducing ripple factor while maintaining low power consumption. The NS architecture is built on a cascade-integrator feedforward (CIFF) structure, using both infinite- and finite-impulse response filters to minimize quantization and kT/C noise. Additionally, it employs a low-power two-stage chopper amplifier to compensate for the offset voltage and enhance system stability. Validated according to the 180 nm CMOS process, the proposed ADC has an effective number of bits of 10.6, a signal-to-noise-and-distortion ratio of 68.4 dB, and a signal-to-noise ratio of 59.33 dB. With a compact area of 0.17 mm2 and a power consumption of 650 µW from a 1.8 V supply, the proposal is well suited to biomedical sensor applications requiring strict accuracy and low energy consumption.