A 440-μW, 109.8-dB DR, 106.5-dB SNDR Discrete-Time Zoom ADC With a 20-kHz BW

Abstract

This article describes a discrete-time zoom analog-to-digital converter (ADC) intended for audio applications. It uses a coarse 5-bit SAR ADC in tandem with a fine third-order delta–sigma modulator (<inline-formula> <tex-math notation= LaTeX >$\\Delta \\Sigma \\text{M}$ </tex-math></inline-formula>) to efficiently obtain a high dynamic range. To minimize its over-sampling ratio (OSR) and, thus, its digital power consumption, the modulator employs a 2-bit quantizer and a loop filter notch. In addition, an extra feed-forward path minimizes the leakage of the SAR ADC’s quantization noise into the audio band. The prototype ADC occupies 0.27 mm² in a 0.16-<inline-formula> <tex-math notation= LaTeX >$\\mu \\text{m}$ </tex-math></inline-formula> technology. It achieves 109.8-dB DR, 106.5-dB SNDR, and 107.5-dB SNR in a 20-kHz bandwidth while dissipating 440 <inline-formula> <tex-math notation= LaTeX >$\\mu \\text{W}$ </tex-math></inline-formula>. It also achieves state-of-the-art energy efficiency, as demonstrated by a Schreier FoM of 186.4 dB and an SNDR FoM of 183.6 dB.