Design and Calibration of a Digital Thermal Sensor

In this paper, architecture of a digital thermal sensor has been analyzed and developed using 10nm Complementary Metal-Oxide Semiconductor (CMOS) technology. This work proposed to integrate the bandgap- based voltage reference with Analog- to-Digital-Converter (ADC) to realize a digital thermal sensor with improved accuracy. The voltage reference is designed with ̴ 1% inaccuracy from -40°C to 130°C, with a temperature coefficient of 0.64 ppm/°Celsius, Power supply rejection ratio (PSRR) of -40 dB at 10 GHz and a line regulation of 0.12 %/V. Analog voltages generated by Bandgap Reference (BGR) are fed to the ADC having two inputs from a voltage reference for further processing. One is bandgap voltage that is the reference voltage, and the other one is Emitter-Base voltage of a pnp transistor that, is a Complementary to absolute temperature (CTAT) voltage. With These two input voltages, the 8-bit ADC, generates unique raw code at respective temperatures varying from -40°C to 130°C with 10°C step size. Calibration is done then to convert the respective raw codes into the equivalent temperature values. The contribution of this work is to present a design of the bandgap voltage reference and its integration into an ADC, which serves as a temperature measurement device using Cadence Virtuoso tool.