The Readout Circuit Design Of Multi-functional Sensor For Temperature,Humidity And Oxygen

The development of the Internet of Things urgently needs integrated,multifunctional,and intelligent sensors.Temperature,humidity,and oxygen sensors are widely used in scenarios such as smart homes,outdoor sports,industrial mines,etc.These three sensors are currently mostly in the form of discrete devices,and there are few studies on the integration of the three sensors.Based on the introduction of the temperature,humidity and oxygen discrete sensors and the related mechanisms of their readout circuits,the paper designs a low-power readout circuit for the temperature and humidity oxygen multifunctional sensor.The circuit mainly includes a bandgap reference circuit and a low-dropout linear voltage regulator.The four modules of the sensor,the sensor preprocessing circuit and the switched capacitor amplifier.The pre-processing circuit is used to convert the three environmental signals into voltage values within a suitable range,and then time-multiplexed by the same switched-capacitor amplifier to output the final result architecture,which reduces the total power consumption of the readout circuit.Circuit design and simulation verification based on SMIC 0.13?m process.The main research contents are as follows:(1)Design of power management module.Designed a bandgap reference circuit in current m ode,with a temperature coefficient of 8.75ppm/? and a quiescent current of 31.8?A,which generates a stable temperature signal and reference;the LDO circuit with a buffer stage is designed,PSR is-61.16dB,the quiescent current is 34.77?A,and a stable 1.2V voltage is generated.(2)Design of sensor preprocessing circuit.The temperature sensor preprocessing circuit outputs a voltage of 521.4?678.4mV in the range of-40?60?;the oxygen sensor preprocessing circuit outputs a voltage of 521.23?679.96mV in the range of 5%?30%.(3)Design of switched capacitor amplifier.The ring amplifier has the advantages of output swing rail-to-rail,internal power consumption has nothing to do with the load,and the performance is improved along with the process.The designed variable bias pseudo-differential ring amplifier realizes single-ended input and differential output,the output swing is increased to 2.4V,the loop gain is 92dB,and the quiescent current is 41.08?A.(4)Simulation of the overall circuit.The final output range of the temperature sensor is-937.4?940.7mV,the sensitivity is 18.79mV/?,the linearity is 99.91%,and the accuracy is 0.09?;the final output range of the humidity sensor is-1.081?1.081V,and the sensitivity is 27.03mV/(%RH),the linearity is 99.99%,the accuracy is 0.01%RH;the final output range of the oxygen sensor is-949.5?951.6mV,the sensitivity is 76.03mV/(v/v%),the linearity is 99.94%,and the accuracy is 0.018%.The overall circuit works normally at a switching frequency of 20KHz,and the quiescent current is 132?A.The simulation result shows that the designed circuit has realized the predetermined function and reached the design index.