The Design Of The Capacitive Humidity Sensor Interface Circuit Based On 0.18?m CMOS Process

The interface circuit is a transition circuit that connects the sensor with the computing circuit.In order to obtain and transform the measured humidity and make it a useful electrical signal,it is necessary to study the interface circuit of the sensor.The principle of the all-digital interface circuit is simple structure is not complicated,the static current is small,the power consumption is low,and the integration is high.Therefore,it has a wide range of applications and lasting development in various semiconductor products.In this paper,a capacitive interface circuit based on TSMC 0.18?m standard CMOS process is designed by using cadence vituoso 617 software.According to the development status at home and abroad,the design index of this paper is proposed.The sensor adopts interdigital electrode structure,and analyzes the range of capacitance when humidity changes,which provides theoretical basis for circuit simulation.The interface circuit is designed based on the principle of CDC detection.The circuit adopts digital structure,including three modules:ring oscillator,shaping circuit and counter.The oscillator is limited amplitude oscillator,shaping circuit is based on second-order differential operational amplifier,and counter is composed of D trigger which can be controlled by clock.The simulation results show that the power consumption is only 0.6?w under 1.2V power supply.Compared with the traditional inverter structure oscillator,this design reduces the power consumption by about 60%,the effective bit is7 bits,the response time is 2ms,and the chip area is 0.126×0.098mm~2.It has good linearity and stability performance,and is suitable for capacitive humidity sensor.