Research And Design Of A2-1Cascade Sigma Delta Modulator

In the twenty-first century, the global electronics market has an explosivedevelopment, which has brought opportunities for China, especially in the electronicsindustry in the semiconductor industry. ADC is attracting people’s attention for areason, our handheld devices, computer and other processed signals to digital signals,digital signals has good characteristics such as flexibility and stability. And wehave contacted the world of the signal for analog signals, so the ADC as a bridgeconnecting the analog world and digital world, its role is self-evident. It can convertanalog signals into digital signals, convenient for data storage, processing andtransmission. For the ADC, due to its different types, so we can select according tothe different needs. For sites requiring high precision usually using sigma delta ADC,in particular its data transformations can be reached with the perfect combination ofdigital signal processing.In this paper, according to the index requirements, we selected architectureand various parameters, and finally decided to adopt the2-1cascade structure, Thenwe did the work of verify by using the Simulink MATLAB module, has reached thedesign requirements. Based on the main circuit of modulator parameters, each subcircuit of sigma delta modulator are designed, including two non overlapping clockcircuit, a fully differential operational amplifier and a comparator, and built the wholecircuit modulator, Through simulation we get the work performance of modulator toachieve ENOB16bit, signal to noise ratio up to102.2dB, to meet the requirements ofour design.After completing the circuit level design, we carried out the layout drawingwork, The CHRT0.18μm CMOS process are used, we each module of the circuitlayout for drawing, and the whole territory through the DRC and LVS detection.This Sigma-Delta modulator’s structure is simple. It has high effective accuracy andlarge dynamic range, the chip area is small. It has practical significance.