A 1.3-µW −0.3/+0.27°C Inaccuracy Fully-integrated Temperature Sensor Based on a Pre-Charge Relaxation Oscillator for IoT applications

This paper presents a CMOS fully-integrated temperature sensor based on a relaxation oscillator for IoT applications. To reduce power consumption, this sensor utilizes the half-period pre-charge compensation relaxation oscillator and uses a time-to-digital convertor (TDC) instead of analog-to-digital convertor (ADC) to count. Besides, the current distribution circuit is employed to improve temperature accuracy. The proposed sensor is implemented in 0.18 μm CMOS and occupies an area of 0.11 mm ² . Measurement results show that the temperature sensor achieves an inaccuracy of -0.3/+0.27 °C across -15°C to 65°C after 2-point calibration. The chip consumes 1.3 μW at 27°C with a 650 mV voltage supply.