Design Of Zoom Analog-to-digital Converter In MEMS Digital Gyroscope

In recent years,with the rapid development of Internet of things,intelligent equipment and precise signal measurement,high-precision MEMS(Micro Electro-Mechanical Systems)digital gyroscope has been widely used in various portable detection equipment,with the development of MEMS digital gyroscope and its interface circuit,the internal Analog-to-digital converter of electronic equipment becomes the bottleneck of sensor performance.The traditional ADC can not be used for both accuracy and power consumption,so it becomes more and more important to study the new ADC.In this paper,the ADC structure of Zoom type is applied to the field of MEMS gyroscope,and the ADC types available in this field are expanded.Firstly,the working principle of Zoom type ADC and its successive approximation(SAR)ADC and Sigma-delta modulator are studied;Then,the system-level model is built by simulink software in Matlab to simulate the system of Zoom ADC,and the feasibility of the whole scheme is verified;Then,a qualitative study of the non-ideal factors such as the noise that may appear in the actual circuit is carried out to determine the main factors that affect the overall performance of the Quantitative analysis,the Circuit Design Index of each unit module is determined by non-ideal model simulation;Finally,according to the circuit parameters obtained by system simulation,the specific circuit structure meeting the requirements is determined,in Cadence Spectre circuit design software,the transistor-level circuit is designed by0.35 um BCD low-voltage process.The improved ADC structure of SAR is used to simplify the design and improve the reliability of the circuit,the high-speed and high-precision comparator is used to compare the signals,and the offset voltage in the circuit is eliminated by using the offset memory technology.The Sigma Delta modulator uses high energy efficiency operational amplifier to further reduce the overall power consumption of the system.The transient simulation of the whole circuit system is carried out,and the differential sine signal with an input frequency of 10 KHz and an amplitude of ±4V is obtained,which is similar to the output of multi-bit quantized structure,the output signal is sampled and Fast Fourier transform to obtain the results of a Spectral density with an interval of 10 Hz.The signal-to-noise ratio(SNR)of a Zoom ADC in the 100 Hz bandwidth range is 123.8 d B,the effective bit number is 20.28 bits,and the dynamic range is greater than 124 d B,the total current consumption is 3.7 m A at5 V supply voltage,which meets the design requirements.