The development of automotive industry is always the most important of all in the world. It would have a broad influence to electric machinery, steel, and relative components. The automotive electronics are keep on developing in high speed because of the highly intelligence requirement to vehicle comfort, safety and information entertainment. So right now the automotive electronics cost would take a huge part of around 30%~50% in a whole car. The automotive electronics systems would generalized be divided into power train system, chassis suspension system, safety system, body electronics system, security system and vehicle telematics system. For example of the category of safety system, there are advanced driver assistance system(ADAS), lane drift warning system(LDWS), front collision warning system(FCWS), night vision system(NVS) and parking assistance system(PAS) which are all hottest development right now. These numerous demand of vehicle electronic system drive the high speed development of automotive electronic component and semiconductor, and also attract a lot consumer electronics companies step into automotive electronic market. Such as the CarPlay of Apple and Android Auto of Google, all their purpose is to make use of touch panel for integration of temperature control, status of traffic, information of vehicle body and capability of internet. It help forward to smart phones and wearable electronic devices get combination with vehicle body for making more close and comfortable life between human and car.
It is a important issue to communicate and transfer data among these numerous automotive electronic systems. The cost would be too high and gain the weight of vehicle body. That's why there are so many serial transmission protocol interface developing to solve these issues. Among many serial interface that CAN bus was regulated by internal standard ISO-11898 and adopting two wire differential transmission technology. If it can't transmit signal because one of the differential lines was broken or grounding malfunction. CAN bus still can change to single line signal transmission mode and obviously lower down the possibility of the bad communication between internal vehicle systems. Furthermore that CAN bus was designed to transmit signal by multi master topology. Each of the master all can automatic transmit signal to specific node for keeping most vacant situation on the bus to deal with massive data transmission. CAN bus would not only enrich the function of vehicle but still would not be influenced by any malfunction of the master node. It could keep the good driving experience for the drivers and decrease the risk of failure repair. The highest applied speed requirement of CAN bus interface is up to 1Mbps and the farthest distance is up to 1000M. So it can satisfy any need about speed and distance of different subsystems inside the car. As so far there are around 70% car have been adopted CAN bus for transmission interface because of the considerations of cost, vehicle weight and specifications.
There are relative transient noises would be occurred because there are many complicated systems inside the car and could frequently contact with human users. The most common transient noise is Electrostatic Discharge(ESD), Electric Overstress(EOS), and Electrical Fast Transient(EFT). ESD event is the charge transfer between two objects. According to human body is easy for charge storage, the damage would be done to automotive electronic devices when ESD event was happened for touching systems inside the car. At present the ESD test standard is mainly according to IEC61000-4-2 including contact and air discharge mode. As for the power transient noise from car inside power supply current break off suddenly, the ignition switch on off, voltage drop from windshield wiper motor in operation. It would follow the ISO7637 conduction transient standard as mainly test specification. The ISO7637 would include Pulse 1(a) to simulate transient event from inductance load at current break off. Pulse 2(b) was to simulate the transient from blowing machine or windshield wiper motor because of the power off in operation. Pulse 3(a)(b) was to simulate the transient noise from switching process. In addition to Electrical Fast Transient(EFT) was in accordance to IEC61000-4-4 for test standard which including power and signal tests.
Amazing Microelectronic Company devoted into Transceiver and Transient Voltage Suppressor(TVS) technology development for over ten years. We make use of self patented techniques to develop CAN bus transceiver AZCAN1042 which could be applied for vehicles, industry, and robot application. AZCAN1042 adopted Silicon on Insulator(SOI) semiconductor process and was designed its fault voltage up to 100V for avoiding overvoltage damage because of the error contact of DC voltage. AZCAN1042 integrated TVS on both signal lines to offer ESD contact mode 12kV and air gap mode 15kV according to IEC61000-4-2 standard. It's not only upgrade ESD protection level but also could take off TVS devices. This way get a great advantage to save PCB space and BOM cost. From the IC single chip protection level, that AZCAN1042 get military regulation with Human Body Model(HBM) 8kV, Machine Model(MM) 800V and Charged Device Model(CDM) 1k. It's latch up free current could up to 400mA and EFT specification could up to 2kV. AZCAN1042 could be the most robust CAN bus transceiver to make sure stable operation performance under tough automotive environment. Besides the excellent specifications of protection ability of AZCAN1042, it's function features are also completely regulated by ISO11898. The common mode voltage of AZCAN1042 could up to 50V and highest speed is up to 2Mbps. There's no doubt that AZCAN1042 could be applied for common power 12V, 24V and 48V system of electric vehicle power.
If it's necessary to enhance additional protection ability of CAN bus, Amazing Microelectronic Company also develop AZ9824-02S with two channels TVS array. AZ9824-02S is a bi-directional 24V protection device in a SOT23 package. The ESD protection level of AZ9824-02S could up to both contact and air gap mode 30kV in accordance to IEC61000-4-2. As for EFT protection level of AZ9824-02S could up to 4kV in accordance to IEC61000-4-4. AZ9824-02S have passed AECQ101 automotive reliability verification to guarantee operation temperature from low temperature -55 degrees Celsius to high temperature 125 degrees Celsius. AZ9824-02S has no problem to applied in tough automotive temperature environment.
Figure 1: The schematic structure of AZCAN1042 CAN bus transceiver.
Figure 2: AZ9824-02S provides ESD and EFT protection function to automotive CAN bus.