Design Of Switched Capacitor Detection Circuit For MEMS Digital Gyroscope

For decades, As the microelectronics technology and manufacturing process of continuous innovation and development, making the IC industry continues to grow. Based On micro- mechanical systems products become more and more common to enter into military and civilian products. Micro mechanical gyro as one of the important branch of MEMS products, Micro mechanical gyro has grown into one of the most potential gyroscope. Therefore, the research of micro mechanical gyroscope has important national defense value and broad market prospect.The can be divided into two parts, mechanical part and electrical part. The mechanical part is the mechanical sensitivity structure of the gyroscope,This article is for the capacitive sensor structure. Electrical part refers to the interface detection circuit gyroscope. Gyroscope interface detection circuit can detect changes in capacitance into a voltage signal. After the signal processing circuit, voltage signal output and the angular velocity of the same changes to achieve the angular velocity detection.In this paper, the micro mechanical gyro detection principle and detection mode are analyzed, established the equivalent model of the structure of micro mechanical gyro sensitive capacitance, and gives the switch capacitance detection circuit system structure and noise analysis. The detection circuit design mainly includes the charge sensitive amplifier, secondary amplifier, sampling hold circuit and the second-order low-pass filter circuit, And to include correlated double sampling circuit to reduce the impact of offset and low frequency noise. Besides, some assistant circuits are also designed, Including the clock control circuit of the pre-stage switched capacitor amplifier, the two-phase non-overlapped circuit, the bandgap reference and the reference voltage generating circuit. Through the simulation, we can get the band gap reference and reference voltage circuit stable working voltage range for the 4.4V-5V. The output voltage are 2.5V. 2V and 1.2V, temperature coefficient respectively for 2.14ppm/oC, 1.678ppm/oC, 1.477ppm/ oC. For detecting circuit simulation can get calibration factor of 28.81 m V/ff, after compensating the temperature coefficient is 86.7ppm/oC scale factor, relative resolution of 7.76x10- 9, the overall power consumption of 9.935 m V, after map simulation, can get calibration factor temperature coefficient is 88.8 ppm/oC, relative resolution of 8.96x10- 9.