A 0.6V–1.8V Compact Temperature Sensor With 0.24 °C Resolution, ±1.4 °C Inaccuracy and 1.06nJ per Conversion
Benjamin Zambrano, Esteban Garzón, Sebastiano Strangio, Giuseppe Iannaccone, Marco Lanuzza
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 0 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ }\text{C}\,\,-100\,\,^{\circ }\text{C}$ </tex-math></inline-formula> 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 0.021mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Experimental measurements performed on 20 test chips have shown very competitive figures of merit, including a resolution of 0.24 °C, an inaccuracy of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\boldsymbol {\pm }1.4~^{\circ }\text{C}$ </tex-math></inline-formula> , a sampling rate of about 1.5kHz and an energy per conversion of 1.06nJ at 30 °C.