A 1.39nJ/Conversion CMOS Temperature Sensor with 173 um2 Sensing Core for Remote Sensing in 65nm CMOS

Yuhang Shui, Linhui Chen, Aili Wang

Abstract: This paper presents a CMOS transistor-based smart temperature sensor for on-chip thermal management. The temperature sensor utilizes proportional to absolute temperature (PTAT) and complementary to absolute temperature (CTAT) currents to control ring oscillators and generate a digital temperature code accordingly. Using a CTAT instead of a constant with temperature (CWT) current as the reference brings two benefits: 1) the dynamic range of the output temperature is enlarged; 2) the design complexity of the reference path is reduced. The nonlinearity introduced by the CTAT frequency can be mitigated in the circuit design by evaluating its Taylor formula. Furthermore, the proposed design supports local and remote sensing by placing the paired PTAT and CTAT sensing elements in a local or remote on-chip place. The nonidealities due to process variation of the sensing elements, the leakage current of the switches, and the parasitic resistance of the long wire are minimized through quantizing the ratio of output frequencies. A prototype sensor occupies 9148 <Formula format="inline"><TexMath><?TeX $\mu {m}^2$ ?></TexMath><File name="a00--inline1" type="gif"/></Formula> with additional 173 <Formula format="inline"><TexMath><?TeX $\mu {m}^2$ ?></TexMath><File name="a00--inline2" type="gif"/></Formula> for local and remote sensing in a 65-nm CMOS technology. After a 2-point calibration, it achieves -0.75/+1.3 °C peak-to-peak inaccuracy over 0 °C to 100 °C. At the conversion time of 375 μs, 0.105 °C resolution is achieved at room temperature. Operating from a 1.0 V supply, it consumes 3.7 μW at 27 °C, which yields <Formula format="inline"><TexMath><?TeX $15.3pJ \cdot {K}^2$ ?></TexMath><File name="a00--inline3" type="gif"/></Formula> FoM.