Design Of A16BitS500KHz Sigma-delta Dac For Silicon Micro-gyroscope

MEMS micro-machined gyroscope has been widely used in the field of aerospace, automotive, military equipment and electronic products for its advantages of integration, miniaturization, intelligent, low power consumption, high reliability, etc. Technologically advanced human societies require specialized tools and equipment to enable their diverse and mobile activities, which means the increasingly high requirements for the performance, size and portable degrees of gyro. Therefore, further digitization of silicon micro-machined gyroscope becomes extremely important, which can significantly improve its performance. In silicon gyroscope interface circuit, the precision of the digital to analog converter level has a significant influence on system performance. This topic mainly aimed at the research of silicon gyroscope DAC interface circuit, three important module of interpolation filter, the sigma delta modulator, low DAC analog reconstruction filter were deep analyzed and implemented.The interpolation filter has achieved64times interpolation function, using three cascaded manner, for each level of FIR filter is detailed introduced in the design process. The first level is the half band filter2times interpolation function: a58order half band filter was designed through the FDA tool, of which the pass band and stop band ripple are within le-4dB, and the stop band attenuation reached97dB. In the second level a1/4band filter was adopted to achieve4times interpolation function, a33order interpolation filter was designed with the stop band attenuation of105dB. The last stage is for sampling hold circuit; the clock frequency was used to achieve8times interpolation function. The result of Simulink simulation shows that the filter meets the design requirements well, the folding structure simulation sampling system is symmetrical in order to save the number of multipliers. The design of interpolation filter signal bandwidth is100KHz, signal-to-noise ratio of106dB.The parameters of the modulator were determined based on the requirement of the system, a5order CIFB structure with the sampling rate of64was chosen to achieve noise shaping function. Through the design of STF and NTF, modulator parameters were achieved and decomposed by CSD code, and the stability has been proved. The signal-to-noise ratio of the modulator is119.7dB, effective digit is19.59bits, which can meet the system requirements according to the simulation.The analog part of sigma-delta DAC is achieved with switched capacitor techniques, high hopping rate "0,1" signal generated by the modulator was converted into analog signal process, followed by the analog low-pass filter to filter high frequency quantization noise. A5order Chebyshev filter was chosen based on the comprehensive consideration of demand and complexity. Finally the simulation part of the circuit was designed and simulated.This paper completes the design of sigma-delta DAC from theory to design, and summed up a set of system design methods. With this method the parameters of DAC can be determined quickly and then system design could be completed well. For further the digital progress of silicon micro-machined gyroscope, it has the very vital significance.