High Precision Audio Sigma Delta ADC Modulator

Sigma Delta ADC has a good compromise between speed,accuracy and power consumption.It has received extensive attention and research in recent years.The accuracy of Sigma Delta ADC used in the audio field is at least 16bit.Well-known audio ADC design companies abroad(such as TI,ADI,Cirrus Logic,etc.)can achieve nearly 18bit accuracy.However,there are very few mature audio Sigma Delta ADC designed by domestic companies.The market of audio ADC is dominated by foreign companies.The main work of this paper is to design a high-precision Sigma Delta ADC modulator applied for audio appication.At the beginning of this paper,the performance parameters of mainstream audio ADC designed by foreign manufacturers and the research papers of domestic universities on audio Sigma Delta ADC modulator are investigated.Then,taking the performance parameters of CS5351,CS5361 and CS5381 designed by Cirrus Logic as the design target.The Sigma Delta ADC modulator designed in this paper is expected to be able to input full-swing analog signals from GND to VDD,the Signal-to-Noise Ratio SNR is at least 110d B and the Signal-to-Noise and Dstortion Ratio SNDR is at least 100d B.This paper adopts the top-down design route.Before selecting the appropriate modulator topology,order,oversampling rate and quantizer bit number,the Sigma Delta ADC modulator system principle and actual circuit hardware overhead are considered comprehensively.Finally,5 order multi-bit quantization Cascade of Resonators Feedforward(CRFF)is chosen as the Sigma Delta ADC modulator structure.After the structure is determined,using MATLAB Simulink to establish the modulator system model and designing program to calculate the model coefficients.In order to solve the nonlinear problem of feedback DAC caused by multi-bit quantization and capacitor mismatch,Dynamic Element Matching(DEM)algorithm is introduced.Then,transistor-level design of the Sigma Delta modulator is completed in Cadence Virtuoso,which mainly includes switch-capacitor integrator,feedforward summation circuit,feedback DAC,multi-bit quantizer,DEM algorithm circuit,etc.The schematic and layout of Sigma Delta ADC modulator are designed in DB Hi Tek 0.18?m Bipolar-CMOS-DMOS Process.Voltage supply is 5V,sampling frequency is 6.144MHz,oversampling rate is 128 and static power is 8m W.The post-simulation results of the Sigma Delta modulator circuit shows that 118.3d B SNR,106d B SNDR and 17.32bit ENOB are achieved,under the condition of 1k Hz,4.45V(-1d BFS)swing sine input signal,which satisfies the expected design performance.In the end,the layout of the Sigma Delta ADC modulator is drawn with an area of 455×335?m~2.