Author:

Keywords:

Science & Technology, Technology, Engineering, Biomedical, Engineering, Electrical & Electronic, Engineering, Noise shaping, Photoplethysmography, Light emitting diodes, Quantization (signal), Fingers, Dynamic range, Ambient light cancellation, chest PPG, dual-slope, dynamic range (DR), light-to-digital converter (LDC), noise shaping (NS), photoplethysmogram (PPG), LOW-POWER, PHOTOPLETHYSMOGRAPHY, AMPLIFIER, INTERNET, THINGS, HEART, SNDR, Equipment Design, Wearable Electronic Devices, 0903 Biomedical Engineering, 0906 Electrical and Electronic Engineering, Electrical & Electronic Engineering, 4003 Biomedical engineering, 4009 Electronics, sensors and digital hardware

Abstract:

This paper presents a low power, high dynamic range (DR), light-to-digital converter (LDC) for wearable chest photoplethysmogram (PPG) applications. The proposed LDC utilizes a novel 2nd-order noise-shaping slope architecture, directly converting the photocurrent to a digital code. This LDC applies a high-resolution dual-slope quantizer for data conversion. An auxiliary noise shaping loop is used to shape the residual quantization noise. Moreover, a DC compensation loop is implemented to cancel the PPG signal's DC component, thus further boosting the DR. The prototype is fabricated with 0.18 μm standard CMOS and characterized experimentally. The LDC consumes 28 μW per readout channel while achieving a maximum 134 dB DR. The LDC is also validated with on-body chest PPG measurement.