Research And Design Of High Precision Sigma Delta ADC For Metrological Applications

Analog-to-Digital converters(ADCs)and Digital-to-Analog converter(DACs)are keys to connect the analog field and digital field.They help people to penetrate the nature of the macro world and explore the laws of nature.With the increasing popularity of electronic equipment in professional fields,social production and daily life,there is a higher and higher demand for ADC which converts analog signals in the macro world.Highperformance ADC has long been a research hotspot in the design of digital-analog hybrid integrated circuits.Especially in today’s daily life,wearable devices are increasing,and ECG and blood oxygen monitoring realized on wristwatches all need ADC to participate in them.In addition to good detection methods,high-performance ADCs are also essential.Like the sensor at the forefront of the logic level,the performance of the ADC is directly related to the accuracy of the signal analyzed by the subsequent application.Sigma Delta ADC is one architecture type of ADC that uses oversampling and noise shaping to improve the circuits’ overall conversion accuracy,with downsampling digital decimation filtering to convert pulse density modulated signals to a more general binary code.Sigma Delta ADC lets analog circuit process low precision signals to reducing the design difficulty of analog part.The digital circuits for high-precision signal processing is ideal for providing high conversion accuracy in scenarios where conversion rate requirements are not very high.Sigma Delta ADC has been widely studied and applied because of its high conversion accuracy and low cost.In this thesis,the overall architecture of ADC is designed according to the ’top-down’idea,and the internal modules of ADC are designed according to the ’bottom-up’ idea.Firstly,the topology of ADC is analyzed and studied,and the similarities and differences between ADCs with different structures are analyzed.So are their application scenarios.The Sigma Delta ADC is then selected as the ADC architecture for the high accuracy,low conversion rate of metrology applications.After determining the architecture,the structure of Sigma Delta ADC is analyzed,and the overall circuit structure of Sigma Delta ADC is determined by mathematical modeling and simulation analysis in MATLAB and Simulink.After determining the circuit architecture according to the behavioral model,the circuit is designed in SMIC 130 nm CMOS process,and the performance of the whole circuit is further optimized by simulating the individual modules and the whole circuit.In the design process,not only the appropriate circuit structure is used to implement the corresponding modules(such as switched capacitor common-mode feedback),but also some techniques that can significantly improve the performance(such as chopper techniques)are introduced.Then the test chip is tested.Under the condition of analog power supply(3.3V)and digital power supply(1.8V),the test chip reaches 18.4 bits ENOB and 15.6 bits noise-free ENOB at rate 10 SPS.The analog power consumption is 1304 m A,i.e.4.3m W,and the digital power consumption is 1.06 m W,which achieves the expected goal of this thesis.