A 0.5-V 180-nm CMOS Switched-Capacitor Temperature Sensor with 319 nJ/measurement

Abstract

In this paper an ultra-low-power switched-capacitor (SC) temperature sensor realized in a 180 nm CMOS process is introduced. The sensor is operational at supply voltages down to 0.5 V, equivalent to the threshold voltages of the available MOS transistors. Using bipolar transistors for reference and temperature dependent voltage generation in a SC band-gap core, the overall temperature sensor is formed by a combination of the band-gap with a time-discrete pseudo-differential single-slope analog-to-digital converter. The temperature sensor has a power consumption of 2.62 µW (4.56 µW) including all biasing and clock generation at supply voltages of 0.5 V (0.8 V), and achieves an estimated 3σ accuracy of 2.42°C (1.36°C) using a two-point trim for the temperature range of 10°C to 100°C (−20°C to 100°C). Besides the temperature sensing functionality, the presented circuitry additionally provides a 24 kHz clock signal and stable reference voltage for other circuit blocks.