The Design Of BiCMOS CAN Bus Transceiver By Reverse Engineering

CAN-Bus is a serial communication bus developed by Bosch in 1980'in order to solve the problem of data exchanged in the instruments of automobiles. CAN-Bus is a system with multiple terminals. The communication medium could be twisted-pair, coaxial-cable or fiber, and the speed of communication can reach up to 1Mbps. CAN-Bus is made up of many nodes, and every node includes mcu, controller, transceiver. CAN transceiver is connected between CAN-Bus controller and the physical bus. It can shift the logic signal from the CAN controller to differential output waves on the CAN bus. At the same time it also receive signals from other nodes and transmit to Can-Bus controller to arbitrate through the receiver.Because of its superior performance, CAN-Bus has been widely used in industrial automation, control equipment, vehicle, medical equipment, environmental control, and many departments. Now in the market, foreign companies'chips are dominant. Many Chinese research institutions have invested a huge amount of financial resource to this field. But most of the R&D is concentrated on the CAN-Bus technology application, while the development of chips is very slow. The development of Chinese CAN bus, chip and protocol standard are very important. It should be taking advantage of the gaps in Chinese CAN bus applications now and with a huge domestic market, develop Chinese own CAN-Bus Interface Chips.The first chapter introduces the methods of IC design. Then, it introduces the problems that reverse engineering is facing in the legal, ethical and other issues and the flow of the reverse engineering. The reverse engineering includes corrosion anatomy ,circuit extraction, analysis, simulation, layout design and output standard GDSⅡ.In the end this chapter introduces the features and performances of CAN-Bus.The second chapter is the analysis of technology and layout of the chip we chose. There are vertical NPN transistors, lateral PNP transistors, NSD/PSD resistance, polysilicon resistors and DMOS transistors in this chip. The transceiver operates at high voltage, so the chip uses extended-drain PMOS transistors and lateral DMOS transistors. Both kinds of transistor can operate at high voltage. At last this chapter introduces other technology in this chip, including electrostatic shield , single-level interconnection and so on.In the third chapter, the circuit extracted from the chip layout is simulated. This chip composed by transmitter module, slope control module, receiver module and overvoltage protection module. Transmitter module is composed by a pair of complementary high-voltage power output transistors and it shift the digital signal which is from CAN controller(TXD) to the differential signal in the bus. When TXD is low, the CANL and CANH are in dominant state, and when TXD is high, the CANL and CANH are in recessive state. Slope control module: Slope control module can limit the rise time(tr) and fall time(tf) of CANL and CANH to reduce EMI. Receiver module: RXD reflects CANL_CANH differential bus voltage in the output pin. The low status of the RXD output pin is dominant in the CAN-Bus and the high status of the RXD output pin is recessive in the CAN-Bus. Overvoltage protection module: When VC_L>VCLmax ,transmitter is off because of overvoltage protection. In this chapter, transmitter module, slope control module and receiver module are simulated and analysed. It can provide some information for overvoltage protection. At last the shortcomings of the chips in achieving functional CAN-Bus is pointed out .It can provide valuable reference information to design.