| Summary: | 碩士 === 大同大學 === 電機工程學系(所) === 98 === A smart temperature sensing system with digital output consists of a temperature sensor and a voltage reference in the front end and an analog-to-digital converter (ADC) in the back end. In this thesis, a threshold-voltage based temperature sensor has been presented, and a low temperature coefficient voltage reference is achieved by using a pn-junction proportional to absolute temperature (PTAT) current generator to compensate the threshold-voltage based temperature sensor. In addition, a 7-bit flash ADC has been designed to convert the output of the temperature sensor to a digital code. The simulation results obtained from HSPICE using a standard TSMC 0.18um CMOS models and 1.8V power supply are presented in this thesis.
This sensor is almost insensitive to the supply and is very linear dependent to temperature. The simulation result shows that the voltage output of the sensor has the temperature error of ±0.07°C from -20°C～100°C, and temperature coefficient of it is -1.239 mV/°C. The low temperature coefficient voltage reference has the result of 1.51V, and the temperature coefficient is 1.058ppm/°C. The 7-bit flash bit has the INL of 0.32LSB, and DNL of 0.38LSB, which can meet the requirement of the temperature sensing system with 1°C resolution.
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