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A 0.6V-1.8V Compact Temperature Sensor with 0.24 °c Resolution, ±1.4 °c Inaccuracy and 1.06nJ per Conversion

Abstract:

This paper presents a fully-integrated CMOS temperature sensor for densely-distributed thermal monitoring in systems on chip supporting dynamic voltage and frequency scaling. The sensor front-end exploits a sub-threshold PMOS-based circuit to convert the local temperature into two biasing currents. These are then used to define two oscillation frequencies, whose ratio is proportional to absolute-temperature. Finally, the sensor back-end translates such frequency ratio into the digital temperature code. Thanks to its low-complexity architecture, the proposed design achieves a very compact footprint along with low-power consumption and high accuracy in a wide temperature range. Moreover, thanks to a simple embedded line regulation mechanism, our sensor supports voltage-scalability. The design was prototyped in a 180nm CMOS technology with a 0C-100C temperature detection range, a very wide supply voltage operating range from 0.6V up to 1.8V and very small silicon area occupation of just 0.021mm2. Experimental measurements performed on 20 test chips have shown very competitive figures of merit, including a resolution of 0.24 °C, an inaccuracy of ± 1.4C , a sampling rate of about 1.5kHz and an energy per conversion of 1.06nJ at 30 °C.