Research On Key Technology Of Integrated Silicon Gyro Interface Circuit Chip With Digital Output

Gyroscopes are sensors which are used to detect angular velocities.They are widely used in science,technology,military,and other fields.Compared with traditional gyroscopes,silicon gyro based on MEMS technology and CMOS technology has the characteristics of low cost,small size,low power consumption,high reliability,and mass production.It not only has a wide range of applications in the civilian field,but also has been obtained in the military field.The silicon gyroscope interface circuit has been chip integrated in foreign countries.Compared with the PCB circuit,it can achieve a smaller volume,better matching with the sensitive structure,higher reliability and electrical characteristics,and the chip integration has not yet been realized in China.The research of silicon gyro integrated interface circuit has important research significance and application value.The following key problems exist in the research of high-performance silicon gyro chips.The existing drive loop stability analysis method cannot analyze the dynamic characteristics of the system,and the analysis of system stability is not accurate enough;the existing noise analysis methods are not perfect,affecting the improvement of gyro noise performance;lack of research on nonlinearity in digital interface circuits will cause harmonic distortion in the system output;China's silicon gyro interface circuit still uses discrete device PCB integration,and integration of interface circuit chips needs to be solved.In order to solve the above problems,this paper studies the following researches on the stability of the drive loop,noise and nonlinearity.Firstly,this paper introduces the principle of silicon gyro self-excited driving circuit,and studies the stability of the driving loop of silicon gyroscope interface circuit,establishes the linearized amplitude control stability model of the drive loop of silicon gyroscope interface circuit,and obtains the system zero-pole diagram.This paper quantitatively analyzes the influence of multiple system parameters on the dynamic characteristics such as system rise time and settling time.According to the stability model,the loop parameters are optimized.Experiments show that the optimized system's start-up time is obviously reduced,which verifies the correctness of the model.Secondly,the silicon gyro noise is analyzed with determination of the main source of circuit noise,and the analytical expression of the system equivalent input noise is obtained.The influence of the noise of the preceding stage circuit on the quantization noise and the effect of the sampling frequency on the quantization noise are analyzed.A noise reduction method for silicon gyroscope interface circuit system is proposed.According to the noise reduction method,the interface circuit is optimized.The test results show that the proposed noise reduction method can reduce the noise level of the detection circuit by 24dB.Finally,based on the nonlinearity from the displacement of the mass to capacitance and the nonlinearity of the capacitance,the nonlinear electrostatic force feedback relation is solved.The nonlinearity in the ?? silicon gyroscope detection circuit is analyzed,and its harmonic distortion component in the output signal is used to characterize and analyze it quantitatively.An electrostatic force feedback linearization method is proposed to reduce the nonlinearity.The test results verify the effectiveness of the method.Based on the above research,a silicon gyroscope interface ASIC chip with closed-loop self-excited driving and digital output was designed,and a 0.35 ?m line width four-layer metal dual poly crystalline BCD process was used for tapeout.The chip area is 4.5×4.0mm2.The silicon gyro system test results of ASIC chip and sensitive structure show that the relative capacitance of the front stage of the detection circuit is 1.8×10-9,the sensor range is ±200°/s,the zero stability is 1.14°/h,and the nonlinearity is 0.017%,the noise is 0.0005°/s/Hz1/2.This paper adopts forward design.The test results confirm the correctness of theoretical analysis,modeling and circuit integration design,realize the chip integration of silicon gyro,and play an important role in the practical and batch application of high performance MEMS gyro.