A DTMOS-based temperature sensor with an inaccuracy of ±0.25°C (3σ) from -20°C to 85°C

Abstract

This paper describes the design of a low-power temperature sensor in a 0.18-μm CMOS technology. The proposed temperature sensor employs the so-called 'dynamic threshold MOS (DTMOS)"diode-connected transistors as the temperature sensing devices. Process spread of the MOSFET threshold voltage is compensated by using the 2-transistor (2T) voltage reference to generate the bias current sources. A charge-balancing delta-sigma $(\Delta \Sigma)$ analog-to-digital converter (ADC) is used to obtain the digital representation of temperature values. The DTMOS temperature sensor core and the ADC operate with 1 V power supply voltages. The ADC operates with a 64- kHz clock frequency and each temperature conversion time is 32ms. After a single-point temperature trimming and a linear fit, the proposed circuit achieves a maximum inaccuracy of ±0.25°C (3σ) across all process corners and the temperature range of -20°C to 85°C, while consuming 8.1 μW.