Design Of Low Power Temperature Sensor Based On The Passive Radio Frequency Identification Chip

After decades of development,RFID(Radio Frequency Identification) technology has been increasingly widely used in various fields, such as transportation, medical, commercial trade automation. Temperature sensor is a very important sensor, which to detect the temperature and control the systems by the temperature characteristics vary with temperature sensor element. The temperature sensor integrated in the RFID tag chip has a wider range of applications. This paper presents an applied passive RFID tag chip which accurate measurement of the ambient temperature with ultra-low power consumption.The temperature sensor includes a temperature detection module and temperature quantization module. The temperature detection module includes a temperature sensing circuit and bandgap reference. First, the principles and the design of temperature detection module which includes a temperature sensing circuit and bandgap reference is analyzed. Temperature characteristics of conventional CMOS processes PNP transistors and operate in sub-threshold region MOS tube are analyzed. In order to meet the low power requirements, the temperature sensing circuit and bandgap reference are implemented by the characteristic of MOSFET which operates in sub-threshold. For match of the input range of the ADC,temperature sensing circuit is improved from 245.7m V to 709.7m V by PTAT current and CTAT current. The temperature sensing voltage range is increased twice. Finally, power and precision are improved to obtain the final structure of the temperature detection circuit.The temperature quantization module uses the low power ADC to convert the temperature-sensing voltage got by the temperature detection module to digital signal. According to the requirements of low power, low sampling frequency and high-resolution, combined with characteristics of various types of ADC, we decided to design a 10-bit SAR ADC. This paper obtains a new type of low power single-ended switching capacitor array by analyzing and optimizing the DAC and it's switching order in the ADC.The reference voltage VREF of the new single-ended capacitor array is half of the traditional reference voltage. The reference voltage of the 10-bit SAR ADC designed is 0.5V, input range is 0V~1V, sampling frequency is 10KS/s, SNR is 57.66 d B,SFDR is 72.48 d B,SNDR is 57.19 d B,ENOB is 9.2, total power is 0.046?W, it meets the design specifications.Temperature detection module and quantization module are integrated, to get the overall architecture of CMOS temperature sensor. Through the simulation in the SMIC 0.18?m CMOS process,the accuracy of the temperature detection can reach ±0.3?, the total power is 0.394?W. The design is suitable for Passive RFID tag chip of temperature detection.