IEEE Trans Biomed Circuits Syst. 2021 Dec;15(6):1224-1235. doi: 10.1109/TBCAS.2021.3130470. Epub 2022 Feb 17.
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 2-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.
本文提出了一种用于可穿戴式胸部光电容积脉搏波（PPG）应用的低功耗、高动态范围（DR）、光到数字转换器（LDC）。所提出的 LDC 采用新颖的 2 阶噪声整形斜率架构，将光电流直接转换为数字码。该 LDC 应用高分辨率双斜率量化器进行数据转换。辅助噪声整形环路用于整形残余量化噪声。此外，实现了直流补偿环路以消除 PPG 信号的直流分量，从而进一步提高 DR。该原型采用 0.18μm 标准 CMOS 制造，并进行了实验表征。LDC 在每个读取通道消耗 28μW 的功率，同时实现了 134dB 的最大 DR。LDC 还通过人体胸部 PPG 测量进行了验证。
