Design Of High Order Switched Capacitor Low Pass Filter In The Interface Circuit With Rapidly-varied Parameter

Traditional active power filter has the disadvantages of low precision and high noise,so it can not meet the requirements of designers gradually.With the progress of integrated circuit technology,switched capacitor circuit has gradually come into people's view.The filter composed of switched capacitor circuit has the characteristics of high precision and high integration,so it has been paid more and more attention.This project comes from the development project of special integrated circuit chip for the signal processing circuit of piezoelectric fast variable parameter sensor.Among them,the low-pass filter is a very important part of the processing circuit.In this design,the second chapter introduces the working mode and theoretical derivation of the basic module of switched capacitor filter,and obtains the advantages of switched capacitor compared with traditional circuit through analysis.After that,the design method of the high-order filter is determined and the non ideal factors of the circuit are analyzed.In the design,simulation tools are used for filter selection and parameter design of high-order bandwidth adjustable low-pass filter.Finally,cascade 4-stage 8-order high-q-low-q-value hybrid second-order Double-four structure is adopted.The simulation results show that the design meets the design requirements.Then,the circuit and layout of the filter are designed by using Huahong 0.35 ? m process.Finally,the filter is taped and tested.The final layout area is 2260 ? m × 2929 ? M.The chip test results show that: the filter can change the input clock frequency to achieve the bandwidth adjustable index of the circuit,specifically to achieve the bandwidth adjustable function of the passband at 1-12khz;in terms of attenuation performance,the attenuation at 18 khz can reach 70 d B@18KHZ The passband ripple can be controlled at about 0.6d B.The performance of the filter meets the design expectation.