A process scalable voltage-reference-free temperature sensor utilizing MOSFET threshold voltage variation

Abstract

This paper proposes a temperature sensing mechanism that utilizes the threshold voltage variation of MOSFETs. The sensor statistically selects two MOSFETs with an appropriate threshold voltage difference to obtain a current ratio proportional to absolute temperature. As the threshold voltage difference acts as a voltage reference, a wide-voltage operation becomes possible without the need for an accurate voltage reference. The sensor sorts the current values during the start-up and automatically selects the two MOSFETs based on predefined rank values. A cell-based implementation of the sensor in a 65 nm bulk low-power CMOS process shows a peak-to-peak inaccuracy of $-0.5/+1.4^{\circ}{\mathrm {C}}$ after a 2-point calibration over $0\sim 100^{\circ}{\mathrm {C}}$, and a line sensitivity of $14^{\circ}{\mathrm {C/V}}$ over 0.8~1.2 V operation.