Optimization Design Of Fieldbus Communication Controller

The paper studies the improvement and optimization of a fieldbus medium attachment unit(MAU)chip.Fieldbus technology is widely used in the field of automatic control.The fieldbus communication controller is an interface circuit in the bus-powered instrument for converting between the signal on the bus and the digital logic signal inside the chip.The MAU chip is a key device for designing the fieldbus communication controller,and the MAU is fully functional.The chip can almost achieve all communication control functions,so it is often called the fieldbus communication controller chip.The MAU chip is a complex system-level mixed-signal chip,which is difficult to design due to the high voltage resistance.In the preliminary work,a circuit compatible with foreign chips was designed by combining the reverse direction and the forward direction,which basically realized the expected functions.However,there are some potential problems because of comparing with the original chip process,the gap is larger.In this paper,several circuit modules have been improved according to the existing problems,including current detection amplifiers,startup control circuits,and reference current source modules in the transmission circuit.The filter module and the digital control circuit in the receiving circuit are optimized.The new design uses the HHNECBCD350 GE process and is designed to take advantage of the high performance bipolar transistors in this process.The paper presents a high common-mode input amplifier based on bipolar transistors,combined with a new start-up control circuit,which realizes the smooth establishment of the current drawn from the bus and the internal supply voltage,and solve the hidden dangers of super pressure that may appear in the original design.The paper presents a low temperature coefficient reference current source design method based on the HHNECBCD350 GE process-specific high current amplification PNP transistor and negative temperature coefficient polycrystalline resistor to improve the temperature characteristics of the chip.For the first time,the paper studies the feasibility of implementing the receive filter in the fieldbus MAU circuit based on Gm-C technology and gives a design scheme.In this paper,a more detailed theoretical analysis of the designed circuit modules is made by the forward design method.In the design,the advantages of the HHNECBCD350 GE process are fully utilized to simplify the implementation of some functions,which reduce the layout area and reduce power consumption.The paper carries out a comprehensive simulation verification of the improved circuit.The results show that the performance of the improved circuit is not lower than the original circuit.The layout of the improved part is given in the paper,and the DRC and LVS layout verification is passed.