Design Of Level Shifter In The Anti-irradiatian DAC Chip

The integrated circuit industry has developed rapidly in our country and some remarkable achievements has been made recently,and integrated circuits are widely applied in both civil and military fields.Some specific integrated circuits need to work under certain adverse environmental conditions which usually puts forward the strict requirements for the stability and reliability of the integrated circuit.For instance,with the development of the aeronautics and astronautics in China,the chips on the spacecraft are on the rise no matter the number or the type,while working environment of high atmosphere and outer space will bring harsh working conditions such as low temperature,cosmic rays and so on,in which it is difficult to ensure regular work and ordinary life of the integrated circuit by general process.For the reason above,the design of high-performance integrated circuits that can work normally and ensure the working life under high altitude adverse factors has become a worthy research direction in integrated circuit design.A digital to analog converter is an integrated circuit that converts digital signals into analog signals,which always plays a key role in the work of signal acquisition and signal processing,and it is applied to control engineering,communication engineering,space engineering and so on.The digital signal has the advantage of stability,anti-interference and attenuation in the process of transmission,while in many cases,the acquisition of analog signals is needed to be processed and analyzed.So the DAC plays an irreplaceable role as the intermediate conversion circuit.A well-working digital to analog converter can store the input digital signal correctly and convert it into the corresponding analog signal.Once a conversion error occurs,it will have a significant impact on the entire system.For this reason,a stable and reliable DAC is necessary.In view of the background above,the following work has been completed in this paper:(1)The background of the project is introduced.Starting with the whole 12 bit four channel DAC chip,a general arrangement of its functionsare made and the DAC chip is dividedinto the several main modules to understand its function better.On the basis of the radiation mechanism required in this project and the understanding of the corresponding radiation strengthening process,the most suitable devices and processes are obtained in accordance with the overall requirements of the chip and the process library.(2)On the premise of the overall requirements above,the design of the level shifter circuit that can work regularly under the three working voltages(-15V~15V,-5V~5V,0~5V)and convert low voltage digital signal to high voltage analog signal is the main work of this paper.Learning and drawing lessons from the traditional CMOS level conversion circuit,the front and rear modules in the chip connected to the level shifter circuit are analyzed,based on which a suitable level shifter circuit with LDMOS transistor is designed.Finally simulations are done and the resultsare obtained.(3)The corresponding layout according to the schematic diagram of the designed level shifter is drawn.Firstly,the principles are sort out that the components involved in the level shifter circuit need to follow drawing the layout.Secondly,the specific layout and wiring of the level shifter are explained.In this paper,the level shifter required for the project is designed,and the specific explanations are made for its functions,working methods,and matters of attention.