Design And Research Of Power System And Transmitter Circuit In Fieldbus MAU Chip

The paper researches technique on fieldbus MAU chip design based on the domestictechnology. Fieldbus is an advanced technology in automatic control field, and fieldbusinstruments have more significant advantages than other instruments. Medium attachment unit(MAU) is the key component of fieldbus instruments, and responsible for conversion betweeninternal logic signals and bus signal. MAU of bus-powered instruments is also responsible todraw current from the bus, and it provides the stable working power. MAU is the designdifficulties of fieldbus instruments. At present, a few foreign companies can provide thisspecial chip. The study of the subject has important significance for improving thecompetitiveness of domestic fieldbus instruments.The paper describes the development status and international standards of fieldbus,mainly introduces and analyzes the mechanism of communication and signal transmissionprinciple of fieldbus instruments using IEC61158-2low speed fieldbus standard, analyzes therequirements of function and performance of MAU. For insight into the working principle andthe design method of MAU, above all reverse analyze chip, extract and clear up the circuit,analyze the working principle and process requirements of the circuit deeply. Because theprocess of domestic is not compatible with the original chip, design a MAU chip compatiblewith the original chip function, with the combination of positive and reverse design, based onthe HHNEC0.35um BCD process. The design retains parts of the original circuit structure, butmany circuit modules are made changes, parts of the module are completely redesigned. Thepaper introduces circuit design, simulation and layout of starting module, constant currentmodule, power system, transmitter, and so on. Making full use of existing technologyadvantages in the design, simplify circuit and reduce the layout area. The paper gives adetailed analysis of simulation results. The results show that the MAU chip is compatible withthe original chip on function. Various performance indicators are better than the original chip.The paper gives the related module layout and overall layout, and layout through DRC&LVS.