Design Of ASIC Digital Module For High-precision Silicon Microgyroscope

Silicon micro gyroscope is the core component of modern inertial navigation and control system.In recent years,the measurement and control circuit of silicon micro gyroscope has gradually developed from discrete devices to special integrated circuits.The main implementation form is digital-analog mixed ASIC.The flicker noise introduced in the circuit analog part and the temperature drift error restrict the accuracy and practicability of the silicon micro gyroscope.In view of the above defects,this paper carried out the research on the design of ASIC digital module of high-precision Silicon micro gyroscope with the goal of improving the accuracy of silicon micro gyroscope and realizing the full digital output with low noise and low power consumption.Firstly,the sensitive structure of silicon micro gyroscope and analog front-end interface circuit designed by our laboratory are studied in depth.The noise characteristics of existing ASIC measurement and control circuit are analyzed,and the design index of digital function module is clarified.The performance,power consumption and chip level implementation difficulty of different digital demodulation algorithms are studied.The optimal algorithm is selected as the implementation basis of digitized phase-sensitive demodulation by simulation and comparison.Secondly,the specific circuit design of silicon microgyroscope ASIC digital core module is carried out.A front-end signal chain preprocessing circuit based on digital filtering system is proposed,and the optimization design of low power consumption and low noise is carried out according to its characteristics.According to the selected optimal demodulation algorithm,a digitized phase-sensitive demodulation circuit that can simultaneously output in-phase demodulation results and orthogonal errors is designed.Comprehensive functional verification and FPGA prototype verification of ASIC digital function modules are carried out.Thirdly,in order to suppress the bias temperature error of silicon micro gyroscope,a real-time temperature error compensation scheme based on ASIC is designed.A zero bias temperature error compensation algorithm using the direct influence of the temperature error of the silicon micro gyroscope such as driving frequency,quadrature error and demodulation phase difference as the compensation source is proposed.In order to obtain the driving frequency to complete the accurate characterization of temperature,a high-precision frequency proposing circuit is designed,and the frequency measurement accuracy of the designed circuit reaches 3.4m Hz.Fourthly,logical synthesis,DFT testability design and static timing analysis are carried out for the digital functional modules designed in this paper,and the layout design of the chip is completed.The power consumption and area of the digital part are analyzed.Finally the chip was the tapeout successfully through TSMC foundry.Finally,the performance of the designed measurement and control ASIC and silicon microgyroscope is tested.The experimental results show that the total power consumption of the digital-analog ASIC for the silicon micro gyroscope designed in this paper is 59.4m W,and the power consumption of the digital module is 15.8m W.The measured normalized noise power spectral density of ASIC is 15.98μV/Hz^1/2,and the the noise of digital part is 5.51μV/Hz^1/2.The maximum calculation range of the digital module theory is±1000°/s.The silicon microgyroscope ASIC system has an 0.38°/h bias instability and 0.05（°）/h^1/2 angular random rate.The maximum scale factor nonlinearity is 8.56×10^-5 in the range of±100°/s.In the temperature range from-40℃to 60℃,the full temperature stability of the silicon micro-gyroscope ASIC system reaches 20.3°/h after real-time temperature compensation.