Design And Research Of Temperature And Humidity Sensor Based On Delta-Sigma ADC

Temperature and humidity signals are the most common analog signals in nature and the environmental signals that human beings are in close contact with in life.Therefore,temperature sensors and humidity sensors in many applications have a strong demand.But most of the sensor is a single discrete sensors,this type of sensor can only for a single signal detection,has great limitations,and integrate multiple sensors together can achieve signal detection at the same time,more predictably,the research direction will be the future sensor is an important research direction,at the same time due to the internal chip to generate heat temperature changes will affect the working state of the whole circuit module,so the chips for the design of low power consumption and the internal working temperature detection chip also is now a hot research topic.According to the current market demand,temperature and humidity sensors are studied in this paper.Firstly,the temperature sensor and humidity sensor are highly integrated on the same chip,which solves the problem that a single sensor cannot measure temperature and humidity at the same time.And the sensor to achieve high precision and low power is studied.In the temperature sensor part,the transistor temperature sensor circuit with high precision and good linearity is first used.The measuring range is-40??60?,and the accuracy is up to ±0.05?.The circuit is integrated in the chip,which can well monitor the working temperature of the chip.The temperature of the chip detected will be compensated and non-uniform calibrated for the whole circuit through the digital back end,which effectively reduces the impact of temperature changes on the whole circuit.Secondly,a resistance temperature sensor with a wider temperature measurement range is designed to measure the external temperature.The temperature sensor circuit realizes the measurement range of-100??100? with an accuracy of±0.1?.At the same time,a humidity sensor which can detect relative humidity in the range of 10%RH?90%RH and the accuracy is less than 1%RH is integrated.At the same time,in the ADC part,the switching volume divider and comparator are designed with low power consumption,so that the power consumption of the whole sensor system is less than 3m W.The main research contents are as follows:1.The circuits of the three modules are designed,and the simulation analysis is carried out.In the on-chip temperature measuring circuit,a band-gap reference with a compensating circuit is used,and the temperature drift factor of this reference voltage should be controlled at about 10 ppm /?.At the same time,the temperature sensitivity of the circuit is about 10 m V/?,and the linearity is 99.9%.For the ambient temperature measurement circuit module,a Whistone bridge circuit is designed and used to detect the temperature signal,and an instrument amplifier is used to amplify it,the temperature sensitivity is about 7m V/?.For the ambient humidity measurement circuit module,the improved switched capacitor circuit is optimized according to the shortcomings of the circuit.The improved switched capacitor circuit is used to detect the humidity signal and obtain continuous signal output.After simulation analysis,each module works normally and meets the design requirements.2.Studied the AD converter,according to the requirements to use Delta-Sigma ADC,according to the analysis of the Delta-Sigma ADC,modulator in the Delta-Sigma overall level and structure level of the research design,the overall level and second-order Delta-Sigma modulator to meet the system requirements under the condition of lower power consumption,at the same time based on the inverter switch electric capacity separator and high speed low power dynamic comparator is studied to achieve the goal that reduce the power consumption of the whole system.Finally,the ADC characteristic parameters were simulated and verified,and DNL was ±0.4LSB,INL was ±0.5LSB,SNDR was 75.355 d B,and ENOB was greater than 12 bit.The performance of each module and the whole system met the design requirements.