Design Of ΣΔADC In The Driving Circuit Of Microgyroscopes

MEMS microgyroscope manufactured by MEMS technology has a small size, light weight and high precision. It is widely used in automotive electronics, aerospace andmilitary fields. The MEMS microgyroscope has two parts: sensitive mechanical structure and the interface circuit. and the interface circuit includes a detection circuit and a diver circuit. The detection circuit is able to detect the angular velocity while the drive circuit provides electrostatic-driven incentives in the sensitive structure during working. Analog circuitry is used in the interface circuit of traditional microgyroscope, but the development of analog circuits has disadvantages: poor in matching, uneasy to compensate errors and loud noises. Using digital circuits, however, the control of amplitude and phasecan be easily done by digital algorithms, what’s more, the data of detection circuit output data can be directly input to the micro-controller or computer to process. For all these reasons, the digitization of the microgyroscope is a research hotspot in recent years.This subject analyzed on the sensitive structure of the vibratory gyroscope, and designed the system of digital self-excited driving circuit on the base of establishing the mathematical model of the sensitive structure by dynamics analysis. This subject also madea theoretical analysis of self-excited loop of microgyroscope and designed the automatic gain control system which contains the amplitude detector, proportional and integral controller. A90°Phase shifter is also designed to compensate the phase shift of the loop.After that, ΣΔADC of single-loop4th-order feedforward, digital decimation filter are designed and simulation optimization. At last, the system-level simulation of micro-gyroscope digital closed-loop self-excited driving circuit the overall structure are done and theresults show that the drive system can be started quickly as the self-noise signal amplificed and to achieve a steady increase self-excited oscillation. The system functionality has been verified.After completing the design of digital driver system of the microgyroscope and functional verification, The project design the core module-ADC. Single-loop4th-order feedforward ΣΔADC is designed using switched-capacitor circuits. In order to achieve the integrator of the fully differential switched-capacitor circuit structure, two-stage differential operation amplifier was designed. Single-bit quantizer is also achieved by using comparator circuit. The simulation of overall system performance of the ΣΔADC circuit is d one by using Hspice software, and the final output data of simulation was analyzed by FFT using Matlab. The result of simulations showed that under the sampling frequency of33MHz, the ratio of the output signal and the quantization noise power density can reach102dB, which has met the requirements of the digital driver system of microgyroscope.