A Comprehensible Guide to Controller Area Network

The Controller Area Network (CAN) is a serial communication protocol designed for providing reliable high−speed data transmission in harsh environments. CAN system designers are being challenged to meet stringentElectromagnetic Interference (EMI) and Electrostatic Discharge (ESD) standards and increase reliability, whilereducing the size and cost of their products. This document provides guidelines to select a CAN bus protection circuitthat can prevent conducted and radiated EMI and ESD noise problems. The attributes of several practical CAN busprotection circuits will be analyzed using discrete filters, common mode chokes and Transient Voltage Suppression(TVS) devices.

Bus protection circuits are used to supplement the noise immunity level of CAN transceivers. Many of the secondgeneration CAN transceivers meet the minimum transient overvoltage test levels; however, higher immunity levels can be easily achieved by adding external EMI/ESD protection circuits. The CAN bus protection circuits improve the reliability of the CAN module, without significantly adding to the cost and complexity of the transceiver circuit.

Control systems can be implemented using either a centralized or a distributed architecture. A centralized control system typically consists of a single, relatively complex control unit that is used to perform multiple tasks and monitor several sensors. In contrast, a distributed control system consists of many controllers that perform a specialized task. The sensors, actuators and motors in a centralized system require point to point wiring in order to exchange information with the control unit, while a distributed system requires only a few wires to connect all of the control units. Also, each control unit in a distributed system, such as the CAN bus can be implemented with a low cost microprocessor.

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