A Compact Temperature Sensor at 1.8µA per Hz Conversion Rate and 1.1 °C Accuracy for SOCs

Abstract

A compact (0.1 mm2 area) temperature-recording system that is suitable for easy integration into an SOC is described. It includes a PTAT sensor, a pre-amplifier, and a first-order sigma-delta modulator based ADC all operating at 1.2V supply. The switched-capacitor pre-amplifier uses an auto-zeroing scheme based upon capacitive reset to avoid the need for shorting the op-amp outputs and inputs during reset. Errors due to transistor leakage are eliminated by selective use of thick-oxide transistors in the design. Another contribution of the paper is to illustrate a scheme that uses two reference voltages in the sigma-delta modulator ADC corresponding to the minimum and maximum temperatures measured to improve its effective resolution.