connectionS and PortS
18
120 Ω
CAN_H
Bus lines: max. 40 m
Stub lines:
max. 0.3 m
CAN_L
120 Ω
CAN
device
CAN
device
CAN
device
CAN
device
Fig. 5: Highspeed CAN
Cable lengths for highspeed CAN bus
The cabling characteristics and the desired bit transmission rate affect the allowable cable length.
ISO-11898 standard specifies a maximum bus length of 40 m and a maximum stub length of 0.3 m with a
maximum of 30 nodes for a bitrate of 1 Mbit/s. However, with careful design, users can have longer cables, longer stub
lengths, and many more nodes to a bus. A large number of nodes requires a transceiver with high input impedance
and each node should be analyzed for signal integrity problems.
Characteristics of two-wire differential bus:
`
Impedance: 108 Ω min., 120 Ω nominal, 132 Ω max.
`
Length-related resistance: 70 mΩ/m nominal
`
Nominal specific propagation delay: 5 ns/m nominal
For further information see ISO-11898 and CiA 102 specifications.
Termination
CAN_H and CAN_L are transmission lines. If the transmission line is not terminated, each signal line causes reflections
which can cause communication failures therefore both ends of the cable have to be terminated. If multiple devices
are connected only the devices at the ends of the cable need to be terminated. Recommended termination resistors in
a highspeed CAN bus topology (according to ISO-11898): 120 Ω.
The TRION-CAN module offers a programmable termination resistance, either high impedance or 120 Ω.
Optional accessory
TRION-CBL-D9-OE-05-00
High quality cable from D-SUB-9 socket to open end, 5 m.
TRION-CBL-D9-CPAD-01-00
High-quality cable from D-SUB-9 socket to CPAD, 1 m.
Active sync LEDs
Active mode LEDs
The 4 LEDs indicate the active synchronization source and the current synchronization
status by flashing the respective LED.
Tab. 3: Active sync LEDs