This paper reports on a low-power readout IC (ROIC) for high-fidelity recording of the photoplethysmogram (PPG) signal. The system comprises a highly reconfigurable, continuous-time, second-order, incremental delta-sigma modulator (I–ΔΣM) as a light-to-digital converter (LDC), a 2-channel 10b light-emitting diode (LED) driver, and an integrated digital signal processing (DSP) unit. The LDC operation in intermittent conversion phases coupled with digital assistance by the DSP unit allow signal-aware, on-the-fly cancellation of the dc and ambient light-induced components of the photodiode current for more efficient use of the full-scale input range for recording of the small-amplitude, ac, PPG signal. Fabricated in TSMC 0.18 μm 1P/6M CMOS, the PPG ROIC exhibits a high dynamic range of 108.2 dB and dissipates on average 15.7 μW from 1.5 V in the LDC and 264 μW from 2.5 V in one LED (and its driver), while operating at a pulse repetition frequency of 250 Hz and 3.2% duty cycling. The overall functionality of the ROIC is also demonstrated by high-fidelity recording of the PPG signal from a human subject fingertip in the presence of both natural light and indoor light sources of 60 Hz.

中文翻译：

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一种 280 μW、108 dB DR PPG 读出 IC，具有可重新配置的二阶增量 ΔΣM 前端，用于直接光数字转换

本文报告了一种用于高保真记录光电容积图 (PPG) 信号的低功耗读出 IC (ROIC)。该系统包括一个高度可重构、连续时间、二阶、增量 delta-sigma 调制器 (I–ΔΣM) 作为光数字转换器 (LDC)，一个 2 通道 10b 发光二极管 (LED) 驱动器，以及集成数字信号处理 (DSP) 单元。间歇转换阶段的 LDC 操作与 DSP 单元的数字辅助相结合，允许信号感知、动态消除光电二极管电流的直流和环境光感应分量，从而更有效地利用满量程输入范围用于记录小幅度、交流、PPG 信号。PPG ROIC 采用 TSMC 0.18 μm 1P/6M CMOS 制造，具有 108.2 dB 的高动态范围，平均功耗为 15.7 μW。LDC 中为 5 V，一个 LED（及其驱动器）中的 2.5 V 为 264 μW，同时以 250 Hz 的脉冲重复频率和 3.2% 的占空比运行。ROIC 的整体功能还通过在自然光和 60 Hz 室内光源存在的情况下高保真记录来自人类受试者指尖的 PPG 信号来证明。