An 11 nW, ＋0.34 °C/−0.38 °C inaccuracy self-biased CMOS temperature sensor at sub-thermal drain voltage

Abstract

This paper presents a low-power, high-accuracy self-biased full CMOS temperature sensor based on sub-threshold currents at sub-thermal drain voltage. The sensor achieves high accuracy and minimal corner dependence by generating sub-threshold current ratios using NMOS transistors of different sizes operating at sub-thermal drain voltage. The proposed self-biased all-CMOS temperature sensing architecture enhances sensitivity by up to seven times and improves linearity. The overall stability under temperature fluctuations is significantly enhanced by utilizing a substrate diode structure that maintains constant current variation. Additionally, a high-threshold comparator with a fast response compresses the oscillator reset voltage difference, enabling ultra-low power operation. Timing logic control is employed to discard unstable cycle outputs, thereby reducing errors and achieving high-accuracy outputs. Operating at 1 V, the circuit consumes only 11 nW at 27 °C in a 180 nm CMOS process. It achieves a peak-to-peak inaccuracy of ＋0.34 °C/−0.38 °C from −10 to 100 °C after two-point calibration, with a resolution of 40 mK and a resolution FoM as low as 3.7 $\text{pJ}{\text{K}}^2$.