32.4 A 1V-Supply $1.85\mathrm{V}_{\text{PP}}$ -Input-Range 1kHz-BW 181.9dB-FOM<sub>DR</sub>179.4dB-FOM<sub>SNDR</sub> 2<sup>nd</sup>-Order Noise-Shaping SAR-ADC with Enhanced Input Impedance in 0.18μm CMOS
Geunha Kim, Se‐Hwan Lee, Taeryoung Seol, Seungyeob Baik, Yeonjae Shin, Gain Kim, Jong‐Hyeok Yoon, Arup K. George, Junghyup Lee
Abstract
Wearable devices rely on accurately read bio-potentials such as ECG, EEG, EMG, and EOG (ExG) to track health. Specifications-wise, such a system requires an input-referred-noise (IRN) <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$< 5\mu\mathrm{V}_{\text{rms}}$</tex> , input impedance <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\mathrm{Z}_{\text{IN}}) > 10\mathrm{M}\Omega$</tex> and BW <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\sim$</tex> 1kHz to readout ExG signals accurately [1]. In addition, a linear-input-range (IR) <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$> 1\mathrm{V}_{\text{pp}}$</tex> is desirable to avoid saturation when motion/stimulation artifacts are present. Furthermore, the above has to be achieved energy-efficiently <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\text{FOM}_{\text{SNDR}} > 175\text{dB})$</tex> and at power envelopes <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$< 10\mu\mathrm{W}$</tex> to reduce battery recharge-cycles.