A Time-Domain Band-Gap Temperature Sensor in SOI CMOS for High-Temperature Applications

This brief presents a temperature sensor operating over a wide temperature range from 25°C to 225°C for oil well instrumentation applications. The temperature sensor is implemented with a simple time-domain architecture and a mapping function at the digital back end. The mapping function eliminates the need for a band-gap reference, whose temperature coefficient deteriorates the accuracy, particularly for high and wide temperature range of operation. The time-domain implementation results in low power consumption and chip area. With digital calibration at room temperature using a field-programmable gate array, the sensor achieves a worst case inaccuracy of +1.6 °C/ -1.5 °C and consumes only 20-μA current under a 4.5-V supply. The chip is fabricated with a commercial partially depleted silicon-on-insulator CMOS process and occupies a chip area of 0.41 mm².