Automotive Communications--EE Architecture Evolution

EE architecture, or Electrical/Electronic Architecture, refers to the design and organization of the electronic/electrical system of a car, including hardware, software, network, interface and other aspects. This architecture is the basis for the intelligentization, digitization and networking of cars, and is also the key to supporting high-level autonomous driving. With the increase in car functions and complexity, the traditional EE architecture has been unable to meet the demand. Therefore, more and more car companies have begun to launch a new generation of EE architecture to improve the performance, safety, efficiency and scalability of cars.

The design of EE architecture not only involves the integration of vehicle hardware and software such as sensors, actuators, ECU (electronic control unit), wiring harness, operating system, etc., but also includes the realization of efficient signal transmission and wiring harness layout in the vehicle. This design needs to comprehensively consider the difficulty and cost of customer functional requirements, installation, configuration, maintenance, etc., and needs to be moderately advanced to adapt to the development of automotive technology and new demand challenges.

The evolution of automotive EE architecture can be divided into three generations. The first generation is planar architecture, also called distributed architecture. The second generation is domain control architecture. The third generation is regional control architecture.

The first generation is distributed, and each electronic function has its own electronic control unit ECU, but the shortcomings of this architecture are also obvious. Each ECU is basically in a closed network state, unable to achieve functional coordination, and unable to have remote OTA upgrades. At the same time, with the update and iteration of automobiles, the requirements for electronic functions are becoming more and more abundant, and there are more and more ECUs on the car. Each ECU is independent, and each ECU needs a wire harness to control and transmit information. Therefore, this architecture is complex and difficult to expand. At the same time, the CAN/LIN/Flexray low-speed network used for communication affects the timeliness of information transmission.

The second-generation Domain control architecture divides domains according to functions. For example, Dr. Bo divides the whole vehicle into five domains: power train, chassis, body/comfort, cockpit/infotainment, and autonomous driving domain (ADAS). Each domain has its own core domain controller and communicates with other functional domains through the gateway domain to create a unified vehicle system. Grouping by function makes the division of labor very clear on the surface, but it does not solve the problem of too many cables. Despite this, the domain control architecture has changed the way cars operate, achieving efficient communication between functional domains through high-speed Ethernet, and changing the way cars are manufactured, updated, and maintained.

The third-generation Zonal regional control architecture is also divided into regions, but it is mainly classified according to physical location. Tesla Model 3 is the first car to adopt this architecture. It is divided into three areas: front body, left body, and right body. Three regional controllers ZCU are arranged to install the devices in the area. All end actuators are connected to ZCU nearby, which becomes a typical IT computing architecture. The external connection of the area is through the regional controller or gateway of the area, and the cable is relatively short and simple. The communication link between the regional gateway and the central computing cluster can be achieved through a small number of high-speed network connections, which may be composed of a small number of twisted pair cables. Even if the backup requirements of safety-critical systems are taken into account, the amount of copper cables used in the entire car body will be greatly reduced.

Regional Controller ZCU Gateway Framework

The overvoltage and overcurrent protection products of different ports are briefly listed. The main thing is that the power port needs to add a fuse or pptc as overcurrent protection. At the same time, it may be subjected to a 5A/5B load dump surge waveform, so the power port is added with a TVS of that rate. The rest are electrostatic protection for CAN/Lin/LVDS and Ethernet ports.

Automotive Ethernet is the backbone of regional control architectures

Through a simple introduction to Ethernet standards and a comparison between CAN/LIN in the Ethernet domain, the Open Alliance is introduced, a non-profit industry alliance for automotive domain technology, which aims to achieve large-scale adoption of Ethernet connections in automotive networks.

The Open Alliance standard requires the operating voltage to be 24V, but the electrostatic trigger voltage needs to be more than 100V, and it needs to be clamped down after being triggered. This requirement cannot be achieved by ordinary TVS, and the latest product with a foldback function is needed. The working characteristics can refer to the following VI curve. The product that meets this function is AQ24ETH-02HTG.

CAN ESD is already a common product in the automotive application field, so I will not introduce it in detail here. The product is also a common material in the market, and the same package has 12V, 15V and 36V options.