Design And Realization Of The Interface Circuit Of Capacitive Micro Acceleration Sensor

Nowadays,MEMS(Micro Electro Mechanical System)technology has developed rapidly in the automotive electronics.Micromechanical accelerometer is an important unit in MEMS.It is also an indispensable part of the internet of things research.So the study of its interface circuit is very meaningful.In this paper,on the basis of investigating the research status of micro acceleration sensor interface circuit at home and abroad,the working principle of micro acceleration sensor interface circuit is introduced and the micro mechanical part and its interface circuit are analyzed.Then,a closed loop feedback structure is choosen.The front-end capacitor to voltage(C2V)conversion circuit which converts capacitance to voltage to stand for the acceleration signal changes is designed and realized.Sigma-Delta modulator is used to quantize the front-end output signal and realize feedback from output to input.Considering the stability of the closed loop system,additional design as signal modulation circuit,compensating circuit are required.The influence of the non-ideal characteristics on interface circuit system is moduled and analyzed in Simulink and the solution is provided.To lower the non-ideal of operational amplifier,the gainboost and CDS(Correlated Double Sampling,correlation double sampling)technology are adopted.High-performanced bootstrap switch is used to be a sampling switch to reduce the nonlinearity of switch.To restrain clock jitter,clock feed-through and charge injection,128 times oversampling is employed and the modified clock circuit which generates two other clock phases turned off in advance is adopted.To eliminate sampling thermal noise,chopping technology is put into use and the sampling capacitance value is optimized.To reduce power consumption,dynamic locking comparator with input misalignment calibration is adopted.Digital Down sampling filter are designed and realized in Matlab too.In this paper,the circuits are realized in SMIC 0.18?m 2p4m process design.The layout design rules and noise questions are considered before the system layout is completed.The post-simulation result of Sigma-Delta modulator is showed that the worst SNR is 73.3dB,the effective value is about 11.3bits.The final equivalent input noise is 4Vrms,the static power dissipation is about 2.2mW and the layout area is 1.2mm~2.The performance of the circuit can meet the design requirements.