Can Bus Termination

High-Speed CAN Termination

For high-speed CAN, both ends of the pair of signal wires (CAN_H and CAN_L) must be terminated. This is because communication flows both ways on the CAN bus. CAN_L is pin 2 and CAN_H is pin 7 on the standard 9-pin D-SUB connector. The termination resistors on a cable should match the nominal impedance of the cable. ISO 11898 requires a cable with a nominal impedance of 120 Ω; therefore, you should use 120 Ω resistors for termination. If you place multiple devices along the cable, only the devices on the ends of the cable need termination resistors. Figure 1 shows an example of how to terminate a high-speed network.

Figure 1. Terminating a High-Speed CAN Network

Electrical termination of a signal involves providing a terminator at the end of a wire or cable to prevent the signal from being reflected back from the end, causing interference.The terminator is placed at the end of a transmission line, designed to match impedance and hence minimize signal reflection.

• Controller Area Network,commonly known as CAN Bus, uses terminators consisting of a 120 ohm resistor