A 14.9-µW Quasi-Passive Error-Feedback Noise-Shaping SAR Converter with 78-dB Dynamic Range for Audio Activity Detection

This paper introduces a quasi-passive Noise-Shaping Successive Approximation Register Analog-to-Digital converter (NS-SAR ADC) suited for low power Audio Activity Detection (AAD). Exploiting a 2<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nd</sup> order Error-Feedback (EF) loop filter implemented through a low power open loop amplifier, insensitive to Process-Voltage-Temperature (PVT) variations, and a fully passive Charge-Sharing (CS) summing node, this converter reaches 78 dB of Dynamic Range (DR), achieving a Schreier Figure-of-Merit (FoM<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</inf>) of 165.3 dB. Fabricated in a 65-nm BCD process, the proposed ADC core occupies 0.129 µm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> consuming 14.9 µW from a 1.2-V supply.