A High-Precision and Low-Power Capacitive Pressure Sensor Interface IC With Wireless Power and Data Transfer for a Pressure Sensor Implant

Abstract

This article presents a system-on-a-chip (SoC) for pressure sensors in 180-nm CMOS technology. It can interface with a capacitive pressure sensor with an inductive wireless power supply and data transmission via load-shift keying (LSK). It integrates an analog front end (AFE), bandgap references (BGRs), delta-sigma ADC, I2C, RC oscillator, low-dropout regulators (LDOs), shorting control switches, and full-bridge rectifier (Rct). An external coil receives wireless power, which is rectified and regulated to 1.8 V by the full-bridge Rct and LDOs. The AFE samples the capacitance change of the pressure sensor to a voltage that is converted into 19-bit digital data by the delta-sigma ADC, which is then converted into 43 Hz per sample serial data by the I2C block. A temperature sensor is included, and 19-bit measurements are transmitted in serial with capacitance data. Serial data are transmitted wirelessly using LSK. This SoC has a measured accuracy of 1 mmHg between 575- and 900-mmHg absolute with a wireless power supply and wireless data transfer.