A low-voltage low-power CMOS time-domain temperature sensor accurate to within [−0.1,+0.5] °C From −40 °C To 125 °C

We present a novel CMOS on-chip temperature sensor for use in low-voltage low-power applications. The sensor uses diode-connected BJTs to generate a PWM signal whose duty cycle is proportional to absolute temperature with high accuracy over a wide temperature range. The duty cycle is determined with a simple digital counter and converted to a digital code. Compared to other time-domain temperature sensors, our design requires only a single bias current and one comparator to generate the PWM signal. After a digital calibration at two temperature points, the sensor is accurate to within [-0.1, +0.5] °C in the temperature range from - 40 °C to 125°C and ±0.1 °C from 0°C to 125°C. The sensor has been fabricated in a 0.35-μm CMOS technology. It draws only 2.5 μA from a 1.4-V supply, corresponding to a power dissipation of 3.5 μW.