A 4μW, ADPLL-based implantable amperometric biosensor in 65nm CMOS

This paper presents a fully implantable, wirelessly powered subcutaneous amperometric biosensor. We propose a novel ultra-low power all-digital phase-locked loop (ADPLL) based potentiostat architecture for electrochemical sensing. The system is wirelessly powered by near-field RF coupling of an on-chip antenna to an external coil at 915 MHz. Bi-directional wireless telemetry supports data transmission from the sensor to the external reader (uplink) via backscattering, and reconfiguration of the sensor chip over the RF downlink. The 1.2×1.2 mm² prototype is fabricated in TSMC 65nm CMOS process. The potentiostat achieves a 100pA sensitivity over a full scale current range of 0-350nA. The total power consumption of the system is 4μW.