闭环微加速度计接口全差分ASIC电路的设计

哈尔滨工业大学工学硕士学位论文AbstractIn order to realize a high performance closed-loop micro-accelerometer system,the study on full-differential interface circuit was taken in this paper.The circuit is divided into full bridge module,charge sense amplifier module,correlated double sampling and holding module,closed-loop feedback module,low-pass filter and time controlling module.The analysis on error voltage and noise waspresented,as the guidance for circuit optimization.The analysis result shows that,toa given sensor structure,the pre-amplifier's unity gain bandwidth and equivalentinput noise,the charge sense amplifier's feedback capacitance,the system samplingfrequency,the reference voltage source noise and pre-amplifier's input wiringresistance are very important to the system performance.There is trade-off betweenthe sensitivity,noise,setting-up voltage accuracy,system bandwidth and signalfidelity.At last,the optimized circuit has an equivalent input noise of 1.63ug/vHz.The circuit design and simulation were based on 0.5um DPDM 18V/5V processtechnology.The simulation result by Hspice shows that,compared with single-endedinterface circuit,the full differential circuit's zero offset is lower by 71.0%,and thelinearity is improved by 62.5%.The overall system performance is listed asfollowing:under +5V supply and 1kHz acceleration input,the system sensitivity is0.308V/g,the system zero offset is 1.456mV,and the non-linearity is 0.03%.The layout design was finished considering the layout overall arrangement,device matching,noise protection and reliability design.The post-simulation byHspice shows that,the system sensitivity is 0.269V/g and the system zero offset is106.54uV.The affection of PID controller on the system performance was also studied.PID controller can improve the system linearity by 66.7%.To a step input,thesystem responding speed is improved by 31%,and the stabilization error is lowered.The overall system performance is:to 1kHz frequency +1g acceleration input,theoutput achieves stabilization within 1 ms,the system sensitivity is 0.22V/g and thesystem zero-offset is 0.9 mV.Keywords:closed-loop micro-accelerometer,low noise,full differential,correlateddouble sampling,PID controller-Ⅱ-