互補式金氧半溫度感測電路以及能帶隙參考電壓源

Abstract

一個數位輸出的溫度感測系統包括了前端的溫度感測電路、參考電壓源，和後端的類比數位轉換器。本文探討溫度感測系統前端部分的設計，以ADS做電路模擬。藉由CMOS製程中的雙載子接面電晶體，利用其VEB電壓對溫度變化的特性，來完成溫度感測電路、參考電壓源，電路模擬是使用TSMC公司的CMOS 0.25um 1P5M的標準製程參數。在-25℃∼125℃的溫度範圍內，模擬顯示所設計的電路有正比於溫度的感測電壓，其隨溫度的變化率為3.6mV/℃。參考電壓( )為1.21V，溫度係數為8.3ppm/℃。 另外提出一型電路的設計具有參考電壓 的形式。將雙載子接面電晶體的VEB電壓對溫度做二階泰勒級數展開，再以 的線性組合來完成溫度的二階補償。以電流模式的電路架構達到VEB電壓的線性組合，使用TSMC 0.18um標準製程參數，模擬結果可達到當VDD=1.8V時，從-40℃到125℃的溫度範圍，參考電壓為255mV，溫度係數為7.8 ppm/℃，消耗的電流為408uA，消耗的功率為0.73mW（在25℃）。

A temperature sensing system with digital output consists of a front part and a rear part. The front part includes temperature sensor and bandgap voltage reference. The rear part is an analog to digital converter (ADC). In CMOS technology, the BJT device is used as the basic temperature sensor. The base-emitter voltage (VEB) can be approximated as a linear function of temperature. By using it, temperature sensor and bandgap voltage reference can be accomplished. The simulation of the front part using a standard TSMC 0.25um 1P5M CMOS process is presented in the thesis. The designed PTAT (Proportional To Absolute Temperature) circuit has an output voltage in proportion to absolute temperature with 3.6mV / ℃. The reference voltage (Vref) is 1.21V with an effective temperature coefficient of 8.3 ppm/℃ from -25℃~125℃. Further more, A new type of bandgap voltage reference, in the form of , is proposed. We expand VEB(T) into Taylor series. After second-order compensation with one scaling factor a1=1 and a2 =-0.79, we will get a third-order temperature dependency of bandgap voltage reference. With current mode topology, the circuits design achieves a second-order compensation of VEB. It is simulated with the models of standard TSMC 0.18um 1P6M process. From simulation, the output voltage is 255mV with an effective temperature coefficient of 7.8 ppm/℃ for the temperature range -40℃~125℃. Total current consumption is about 408uA and power consumption is about 0.73mW at 25℃ for this proposed circuit.