Research On The Key Technology Of Readout Integrated Circuit Of Temperature Humidity And Pressure Sensor

In industrial and agricultural production,automotive electronics,environmental analysis,climate analysis,military aspects,integrated temperature,humidity and pressure sensors have a very important application.The readout intergrated circuit is the main component of the integrated temperature,humidity and pressure sensor.Its performance directly affects the accuracy and sensitivity of the integrated temperature,humidity and pressure sensor signal readout.The integration of readout circuits for multiple sensors onto a single chip is also a very popular research direction in recent years.This paper mainly studies the key technologies and principles of integrated temperature and humidity pressure sensor readout intergrated circuit.Based on the needs of the project,in view of the scope of variation of the PNP bipolar transistor,humidity sensor,and varistor provided in this study,the readout integrated circuit of the three modules of the temperature,humidity,and pressure sensor was designed and simulated.The readout integrated circuit has the advantages of high sensitivity,good stability,high integration,wide measurement range,and realizes reading of temperature,humidity,and pressure analog signals.This topic selected the CSMC 0.5?m CMOS process for design and simulation of circuit,which has the advantages of low power consumption and high integration.The research results are as follows.1.The design of integrated temperature sensor signal readout circuit was carried out,including temperature sensing module,bandgap reference circuit module and ramp generator.The temperature sensing module uses a PNP bipolar transistor as a temperature sensing element;the bandgap reference voltage source circuit is designed to generate a reference voltage that is independent of the temperature and power supply for the entire circuit.The temperature drift coefficient is 20.18ppm/°C.The reading circuit temperature detection range is-40 °C to 85 °C,the output voltage changes to 3V,the temperature sensitivity is 24mV/K,the output voltage has a linearity of 99.92%,and the slope is adjustable,thus achieving the temperature signal readout.2.The design of the integrated humidity sensor signal readout circuit was carried out,and a novel differential switched capacitor circuit was used as a humidity signal readout circuit including capacitor,CMOS switch,and two-stage operational amplifier circuit.The first stage of the two-stage operational amplifier is a folded cascode operational amplifier.The second stage is a common-source amplifier.The open-loop gain is 73.6dB,the common-mode rejection ratio is 83.5dB,and the power supply rejection ratio is 83.7dB,meeting the readout circuit requirements for the op amp.The size of the sensing capacitor in the readout circuit varies from 4 pF to 5.5 pF,the output voltage has a 1.5 V amplitude shift,and the readout circuit conversion resolution is 1 mV/fF,enabling the detection of a tiny sensing capacitor.3.The design of the integrated pressure sensor readout circuit was carried out,including a constant current source power supply circuit and a signal amplifying circuit.The pressure-sensitive resistors are connected into a Wheatstone bridge circuit structure,and the power supply method is a constant current source power supply method;the signal amplification circuit adopts a three-op-amp instrumentation amplifier structure and the gain is adjustable.When the gain is 40 dB,the equivalent input noise at 100 Hz is 18.87nV/sqrt(Hz),the common mode rejection ratio CMRR is 158 dB,and the power supply rejection ratio PSRR is 128.37 dB,which is consistent with low noise and high common mode rejection ratio.The amplification of the weak differential input voltage and the readout of the varistor variation are realized.