Research And Design Of Key Technology Of High Performance Audio Sigma Delta Analog-to-digital Converter

With the development of artificial intelligence,the interconnection of everything is becoming more and more dense,and the amount of data that needs to be processed is increasing.The analog-to-digital converter is the interface between the real world and the digital world,and high-performance analog-to-digital converters can meet our daily needs.According to the application characteristics of different frequency ranges,the analog-to-digital converter is divided into different architectures.The Sigma Delta analog-to-digital converter has become a hot spot in the current academic and industry research due to its application frequency closer to the daily use range,good noise performance,low power consumption,and good linearity.The inherent anti-aliasing characteristics of the continuous-time Sigma Delta modulator reduces the requirements for the pre-anti-aliasing filter,and there is no requirement for the settling time,so it can save power consumption.Compared with discrete-time Sigma Delta modulators,continuous-time Sigma Delta modulators have better linearity and are more suitable for use in audio products.This article first introduces the basic theory of the Sigma Delta modulator,then introduces the basic circuit structure and compares their advantages and disadvantages.Then the non-ideal effects in the actual circuit such as the limited gain and bandwidth of the integrator,the non-ideal factors of the quantizer,the clock jitter,the matching problem of the DAC,and the change of the RC constant are analyzed,and the optimization method is proposed.By calculating the feed-forward structure,feedback structure and the modulator transfer function of the hybrid structure,the advantages and disadvantages of each structure are analyzed,and finally the hybrid structure is selected as a compromise.Without changing the transfer function,the adder is eliminated and power consumption is saved.After that,the SD Toolbox tool in Simulink is used for system modeling,and behavioral-level simulation is performed to determine the gain coefficient of the circuit.In this process,the uncertainty of the internal quantizer and DAC delay is eliminated through a fixed half-cycle delay.In the circuit-level design,a two-stage operational amplifier with Miller compensation and chopping was used to realize the active RC integrator.The main sources of integrator noise are analyzed and calculated,the bandwidth and gain of the operational amplifier are adjusted to meet the requirements of the modulator,and an appropriate chopping frequency is set to achieve satisfactory noise performance.The quantizer adopts a dynamic comparator and SR latch structure,which greatly improves the working speed of the quantizer to meet the delay requirements of the circuit.DAC adopts current rudder structure to further improve the working speed of the circuit.The feedback waveform adopts NRZ feedback waveform,which reduces the influence of clock jitter on the modulator.Finally,the circuit design and simulation are completed using CSMC 180 nm process.Under the 1.8 V power supply voltage,the clock frequency is 5.12 MHz,the input signal bandwidth is 20 kHz,the front-end simulation result shows that the SNDR is106.4 dB,and the effective number of bits is 17.38 bit.After the layout design,the back-end simulation is performed after the layout design is completed.The result shows that the SNDR is 104.3 dB,the effective number of bits is 17.04 bit,and the power consumption is 0.4554 mW.This paper also carried out the design and simulation of the digital filter,selected the structure of the filter reasonably,optimized the hardware area and filtering performance,and the simulation results reached the expected results.