This paper presents a capacitive pressure sensor interface circuit design in 180 nm XH018 CMOS technology for an implantable capacitive pressure sensor, which has a wireless power supply and wireless data transfer function. It integrates full-bridge rectifiers, shorting control switches, low-dropout regulators, bandgap references, analog front end, single slope analog to digital converter (ADC), I2C, and an RC oscillator. The low-dropout regulators regulate the wireless power supply coming from the rectifier and provide a stable and accurate 1.8 V DC voltage to other blocks. The capacitance of the pressure sensor is sampled to a discrete voltage by the analog front end. The single slope ADC converts the discrete voltage into 11 bits of digital data, which is then converted into 1 kbps serial data out by the I2C block. The “1” of serial data is modulated to a 500 kHz digital signal that is used to control the shorting switch for wireless data transfer via inductive back scatter. This capacitive pressure sensor interface IC has a resolution of 0.98 mmHg (1.4 fF), average total power consumption of 7.8 mW, and ±3.2% accuracy at the worst case under a −20 to 80 °C temperature range, which improves to ±0.86% when operated between 20 and 60 °C.

This paper presents a system-on-a-chip (SoC) for pressure sensors in 180nm 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, delta-sigma ADC, I2C, RC oscillator, low-dropout regulators (LDOs), shorting control switches and full-bridge rectifier. An external coil receives wireless power which is rectified and regulated to 1.8V by the full-bridge rectifier 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 43Hz 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 is transmitted wirelessly using LSK. This SoC has a measured accuracy of 1mmHg between 575mmHg to 900mmHg absolute with a wireless power supply and wireless data transfer.

This paper describes a new dosimeter, which is composed of a Floating-Gate-Radiation-Field-Effect-Transistor (FGRADFET) sensor and novel absorbed-dose and dose-rate readout circuit. It is a single-chip implementation employing a standard single-poly 130nm CMOS technology. The FGRADFET extends the floating-gate as an extra silicon-area (60µm × 200µm) of poly-over-field-oxide that acts as a catchment to sense the radiation from the environment. There is also a parallel array of 16 PMOS transistors (1µm × 2µm each) at the edge of the field-oxide catchment-area to charge the floating-gate by the Fowler-Nordheim tunneling effect prior to the sensor deployment. Thus, no bias voltage is needed for the floating-gate (FG) transistors during the irradiation. A cascode current-mirror, a reference FGRADFET and 16 reference PMOS transistors are employed to compensate temperature effects and read the FG voltage of the FGRADFET sensor, which is proportional to the total absorbed dose. A further processing circuit for the FG voltage output is also designed to extract the slope of the FG voltage (the dose-rate). These circuits include differentiator, pre-amplify buffer, chopper-amplifier, low-pass filter and double-ended-to-single-ended output amplifier. A measured average sensitivity of around 3.86 mV/rad was achieved for x-ray irradiation. It consumes 320 µW in detecting the dose-rate with a 1 rad/min. 10 rad/min measurement range corresponding to the single-ended output ranging from 220 mV to 960 mV.