A 3.9 mW 25-Electrode Reconfigured Sensor for Wearable Cardiac Monitoring System

Abstract—A low power highly sensitive Thoracic Impedance Variance (TIV) and Electrocardiogram (ECG) monitoring SoC is designed and implemented into a poultice-like plaster sensor for wearable cardiac monitoring. 0.1 TIV detection is possible with a sensitivity of 3.17 V and SNR 40 dB. This is achieved with the help of a high quality (factor 30) balanced sinusoidal current source and low noise reconfigurable readout electronics. A cm-range 13.56 MHz fabric inductor coupling is adopted to start/stop the SoC remotely. Moreover, a 5 % duty-cycled Body Channel Communication (BCC) is exploited for 0.2 nJ/b 1 Mbps energy efficient external data communication. The proposed SoC occupies 5 mm 5 mm including pads in a standard 0.18 m 1P6M CMOS technology. It dissipates a peak power of 3.9 mW when operating in body channel receiver mode, and consumes 2.4 mW when operating in TIV and ECG detection mode. The SoC is integrated on a 15 cm 15 cm fabric circuit board together with a flexible battery to form a compact wearable sensor. With 25 adhesive screen-printed fabric electrodes, detection of TIV and ECG at 16 different sites of the heart is possible, allowing optimal detection sites to be configured to accommodate different user dependencies. Index Terms—Body channel communication (BCC), cardiac monitoring, fabric electrode array, healthcare sensor, planar-fash-ionable circuit board (P-FCB), remote control, thoracic impedance variance (TIV), wearable-body sensor network (W-BSN). I