26.1 A 4.5mm2 Multimodal Biosensing SoC for PPG, ECG, BIOZ and GSR Acquisition in Consumer Wearable Devices
26.1 A 4.5mm2 Multimodal Biosensing SoC for PPG, ECG, BIOZ and GSR Acquisition in Consumer Wearable Devices
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26.1 用于消费类可穿戴设备中 PPG、ECG、BIOZ 和 GSR 采集的 4.5mm2 多模态生物传感 SoC
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发表时间：
2020
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通讯作者：
Ping
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作者：
Yun;Zhi;Yu;Su;Wei;A. C. Chiou;Chang;Hung;Fan;Teng;Ping
最近，生物传感器已广泛应用于消费者可穿戴设备中，例如智能手表和腕带，以跟踪用户在运动、睡眠和日常活动期间的健康状况。然而，与控制良好的医疗环境中的生物信号采集不同，消费类设备中的信号采集不可避免地会因传感器接口不良、运动伪影和环境干扰（例如环境光和电源线耦合）而导致信号质量下降，这些干扰可能比所需信号强 60dB 以上。这些挑战导致 AFE 规格要求很高，即使传感器面积、芯片尺寸和电池容量受到严格限制，而这些都是可穿戴设备所必需的。本文提出了一种多模态生物传感 SoC，可解决这些问题，从而在可穿戴设备的高度可变条件下实现可靠的光电容积描记术 (PPG)、心电图 (ECG) 和生物阻抗 (BIOZ) 采集。它包含 130dB-DR PPG 读数，比最先进的技术 [1] 高 11dB，可以承受强烈的环境光；具有伪右腿驱动 (RLD) 的 ECG AFE，可耐受来自电源线耦合的 >130VPP 共模干扰 (CMI)，比 [2] 中提出的技术高 3 倍； BIOZ AFE 使用 1cm2 电极进行体脂测量，而不是传统体脂计中通常使用 >10cm2 的电极。整个 PPG/ECG/BIOZ AFE 的面积约为 3mm2，比具有类似功能的先前 AFE 小约 50% [3]、[4]。
Recently, biosensors have become widely deployed in consumer wearable devices, e.g., smart watches and wrist bands, to track user health conditions during sport, sleep, and daily activity. However, unlike biosignal acquisition in well-controlled medical settings, signal acquisition in consumer devices inevitably suffers from degraded signal quality due to poor sensor interfaces, motion artifacts, and environmental interferences, such as ambient light and power-line coupling, which can be >60dB stronger than the wanted signals. These challenges result in demanding AFE specifications, even under tight constraints on sensor area, chip size, and battery capacity, which are all necessary for wearable devices. This paper presents a multimodal biosensing SoC that addresses these issues to enable reliable Photoplethysmography (PPG), Electrocardiography (ECG), and Bio-impedance (BIOZ) acquisition under highly variable conditions in wearable devices. It contains a 130dB-DR PPG readout, which is 11dB higher than the state of the art [1], to tolerate strong ambient light; an ECG AFE with a pseudo Right-Leg-Drive (RLD) tolerant of >130VPP common-mode interference (CMI) from power-line coupling, which is 3× higher than the technique presented in [2]; and a BIOZ AFE for body-fat measurement using 1cm2 electrodes rather than the typically >10cm2 electrodes in conventional body-fat meters. The area for the entire PPG/ECG/BIOZ AFE is ~3mm2, which is around 50% smaller than prior AFEs with similar features [3], [4].