A 134 dB Dynamic Range Noise Shaping Slope Light-to-Digital Converter for Wearable Chest PPG Applications.

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 signals DC component, thus further boosting the DR. The prototype is fabricated with 0.18 m standard CMOS and characterized experimentally. The LDC consumes 28W per readout channel while achieving maximum 134 dB DR. The LDC is also validated with on-body chest PPG measurement.