A Multi-Channel 100-dB DR PPG/ECG SoC for Smart Wearable Devices

Real-time monitoring of vital signs in wearable devices focuses on accurate photoplethysmogram (PPG) and electrocardiogram (ECG) recording. Motion artifacts, ambient light interference and sensor-skin contact variability affect signal quality significantly, demanding a multi-channel sensor interface chip with a high dynamic range and energy efficiency. A PPG/ECG SoC is proposed for robust signal optimization. Time-division multiplexing, ambient double sampling and DC current compensation together enhance the dynamic range. Fabricated in $0.18 \mu \mathrm{m}$ CMOS technology, the chip features a 5.63-pArms direct digitized input-referred noise for PPG readout and $365-\mathrm{nVrms}$ for ECG. A cross-scale dynamic range of 133 dB is achieved, providing saturation-free usage for sport wearable devices such as smart rings.