A Sub-Threshold Oscillator-Based High-Accuracy Temperature Sensor With Tolerance to Supply Fluctuation and Device Aging
Abstract
Accurate, low-power, and compact temperature sensors are demanded in a wide range of biomedical, environmental, and industrial sensing applications. This article presents an accurate and precise CMOS temperature sensor based on a sub-threshold ring oscillator (RO) in 180 nm. The sensing core employs a five-stage super cut-off contention-free (SCCF) delay cell to closely mimic the temperature dependency of a single MOSFET, minimizing the errors in current-to-frequency conversion and achieving a −0.065 °C/ +0.061 °C inaccuracy after 2-point calibration and ±0.26 °C after 1-point calibration from −20 °C to 100 °C. Meanwhile, a self-biased 3-transistor (3T) header significantly reduces the supply line sensitivity to 0.02 °C/V and achieves less than 0.2 °C temperature drift after more than 180 h of accelerated aging. The aging-induced drift is reduced to 0.11 °C with a calibration after 30 h of pre-aging. Additionally, this work introduces an adaptive uniform resolution counter to maintain a consistent and programmable resolution across the wide temperature range, despite the sub-threshold RO’s exponential dependency on temperature. The prototyping sensor in 180-nm CMOS consumes only 33 nW at 20 °C and occupies 0.028 mm² area. Beyond standard circuit testing, the 1-pt calibrated sensor was validated in a multi-day in vivo animal body temperature tracking experiment and outperformed off-the-shelf solutions.
Wei Wang
PhD 2025, now at Apple
Yumin Su
Ph.D. Student (started in 2023)
Liwen Jiang
MECE 2021, now at NVIDIA
Zhiyu Chen
PhD 2023, now at Apple
Zhanghao Yu
PhD 2023, now at Intel
