Analysis And Design Of Fully Differential Readout Circuit Of A MEMS Acceleration Sensor

With the development of Micro Electro Mechanical System(MEMS),MEMS acceleration sensor has been widely used in petroleum exploration,navigation application,Virtual Reality(VR)and other fields.MEMS readout circuit is mainly through detect of differential capacitance values,and then transform it into a voltage signal,and thus obtain sensitive quality block size of acceleration.The full differential readout circuit is the basis of MEMS acceleration sensor working normally.Its precision determines the maximum performance of all circuit modules.In the practical design,selecting the appropriate circuit structure,setting stable voltage and small non-ideal factors(mainly including noise)are the core problems to be solved.In order to meet the above requirement,the fully differential circuit is very important.In this thesis,aiming at the shortcomings of the traditional MEMS acceleration sensors are designed,analyzed the MEMS acceleration sensor readout circuit,the main work is as follows:1)According to the design demands,0.5-?m CDMOS process based standard technics which designs a kind of used in oil exploration full differential capacitive MEMS acceleration sensor readout circuit.The circuit consists of five modules,including full differential circuit,subtracter,buffer,bandgap reference source and multiple clock generation arrays Among them,the full differential circuit adopts the correlated double sample technology,which can suppress the noise of the circuit and obtain a larger output voltage swing.The buffer adopts chopper stabilization technology,which can reduce input noise and realize resistance matching and band extension.The output voltage is obtained by subtracting the input voltage of the buffer from the input voltage of the same phase and the input voltage of the reverse phase.The bandgap reference source consists of a basic cascade circuit,which provides a reference voltage for the front circuit and the switching circuit to control the opening and closing of the switch.The timing sequence of the multiple clock generation arrays can be programmed to facilitate subsequent linearity static testing.Simulation results show that the circuit has low noise,low temperature drift coefficient and high linearity,2)After that,the layout design and flow test were carried out.The test results show that the reference voltage Vbg of the circuit is 1.32V and VRP is 3.756V.All 12 time series of the switch can be displayed by oscilloscope and meet the design requirements.