A Resistive Sensor Interface IC with Inductively Coupled Wireless Energy Harvesting and Data Telemetry for Implantable Pressure Sensing

In this paper, a system-on-a-chip (SoC) designed to interface a piezoresistive sensor for implantable pressure sensing is reported. It is fabricated in 65 nm CMOS and consists of a resistance-to-time converter, a 915 MHz energy harvester with an on-chip coil and backscatter telemetry. Key technologies to lower power consumption include current-sharing based readout and automatic bias calibration. The chip consumes 9.75 μW and offers pressure sensing at a resolution of 3.1 mmHg over a range of 200 mmHg, in combination with a commercial pressure sensor. It also provides temperature sensing ability with a resolution of 0.18 °C from 25 °C to 62 °C. The chip harvests energy with the on-chip coil and transmits data to an external reader via RF backscatter. Implantation experiment using pork has shown that the chip works at up to 10 mm implant depth with good misalignment tolerance. This low-power sensor interface IC occupies only 0.196 mm2 and the sensing system formed by bonding a commercial resistive sensor to the IC is limited to 0.056 mm
³
in volume, offering the feasibility of long-term continuous pressure physiological indicator monitoring.