This paper presents a continuous-time zoom ADC for audio applications. It employs a high-speed asynchronous SAR ADC that dynamically updates the references of a continuoustime delta-sigma modulator (CTDSM). Compared to previous switched-capacitor (SC) zoom ADCs, its input impedance is essentially resistive, which relaxes the power dissipation of its reference and input buffers. Fabricated in a 160 nm CMOS process, the ADC occupies 0.27 mm 2 and achieves 108.1 dB peak SNR, 106.4 dB peak SNDR and

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... 108.5 dB dynamic range in a 20 kHz bandwidth, while consuming 618 μW. This results in a Schreier FoM of 183.6 dB. Index Terms-A/D conversion, audio ADC, delta-sigma ADC, asynchronous SAR ADC, inverter-based OTA, low power circuits, dynamic zoom ADC, continuous-time delta-sigma.