A Current-Mode Dual-Slope CMOS Temperature Sensor

Abstract

A current-mode dual-slope CMOS temperature sensor is presented in this paper. It employs a proportional-to-absolute-temperature (PTAT) current generator, which operates in the sub-threshold region, and a novel temperature-insensitive CMOS inverter, replacing a traditional voltage comparator for power saving, to create PTAT pulsewidth. A binary counter is then utilized to quantize the pulse to a digital output value. It achieves a temperature inaccuracy of -3.39 degrees C-2 degrees C over the common industrial temperature range from -40 degrees C to 85 degrees C for five measured chip samples by utilizing the second-order curvature correction, and an average temperature resolution of 0.259 degrees C/LSB. The conversion rate of the digital output data is 3.5 kSa/s. The 2 V supply voltage is utilized and the total power dissipation is 14.286 mu W, leading to 4.082-nJ/Sa energy efficiency and 0.274-nJ degrees C-2 resolution figure of merit (FoM). It was fabricated by the TSMC 0.35-mu m CMOS process, and the core area occupies 0.0345 mm(2). The utilized dual-slope architecture has the advantages of compactness, power-saving, and high design flexibility.