A fully digital temperature sensor with 187-μm2 front-end for on-chip thermal management in 55-nm CMOS

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 m2. The temperature sensor achieves a resolution Figure of Merit (FoM) of 208 pJ center dot K2, the power consumption of 7.2 mu W, the resolution of 112 mK, the conversion time of 1.66 ms at 20 degrees C, the max-min inaccuracy of +0.48/-0.46 degrees C and 3 sigma-inaccuracy of +/- 0.73 degrees C from -10 to 120 degrees 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 similar to 4.51 degrees C/V.