A fully digital temperature sensor with 187-\(\mu \text {m}^{2}\) front-end for on-chip thermal management in 55-nm CMOS

Abstract

This article proposes a fully digital temperature sensor with ultra-small sensing front-end for on-chip thermal management. Utilizing the temperature characteristics of MOSFET leakage current, an innovative Leakage-Dominated inverting Schmitt-Trigger (LDST) is proposed. The ring oscillator composed of LDST achieves temperature-to-frequency conversion. Different from the traditional fixed resolution and conversion time within the full temperature range, Adaptive Resolution Frequency-to-Digital Converter (AR-FDC) is proposed to realize faster measurement speed at high temperatures to timely prevent chip overheating while maintaining high resolution at low temperatures. Fabricated with a 55 nm CMOS process, the front-end of proposed temperature sensor occupies a silicon area of just 187 \(\mu \text {m}^2\). The temperature sensor achieves a resolution Figure of Merit (FoM) of 208 \(\text {pJ}\cdot \text {K}^{2}\), the power consumption of 7.2 \(\mu \text {W}\), the resolution of 112 mK, the conversion time of 1.66 ms at 20\(^\circ \hbox { C}\), the max-min inaccuracy of \(+0.48/-0.46^\circ \hbox { C}\) and 3\(\sigma\)-inaccuracy of ±0.73\(^\circ \hbox { C}\) from \(-10\) to 120\(^\circ \hbox { C}\) after two-point calibration. It can operate under a supply voltage ranging from 0.8 to 1.3 V, with a supply sensitivity of 3.02 \(\sim\) 4.51\(^\circ \hbox { C}\)/V.