A CMOS physiological monitoring frontend for wearable health applications

A prototype CMOS physiological monitoring fron-tend for wearable or portable health system is presented. It consists of three main modules for electrocardiography (ECG) recording, bioelectrical impedance (BI) measurement and body temperature (BT) measurement individually. The ECG recording module has a low-noise Instrumentation amplifier with right-leg driver, a notch filter for avoiding power-line interference and an AC-coupled programmable gain amplifier with 28-46 dB. The BI measurement module for body mass index measures the body bioelectrical impedance by a 300 μA/50 kHz AC excitation current. A multi-steps slope analog-to-digital converter (ADC) with sample rate of 500-1000 Sps is designed for digitalizing the analog ECG and BMI value. For power, size and overall cost reduction, electrodes multiplexing technique has been applied in system-level and circuit-level design. This front-end also provides a specified interface module for body temperature sensor DS18B20. Communication to this chip is accomplished using an UART interface. This prototype chip has been designed and fabricated in 0.18 μm 1P6M CMOS process with chip area of 1685×1600 μm².