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CAN bus 120 Ohm cable?
The D10226-0 CAN Bus Cable is a 120 Ohm controlled impedance cable designed to meet the high electrical demand of a CAN Bus cable system. The D10226-0 CAN Bus Cable incorporates design features that provide maximum electrical performance with high strength copper alloy conductors and silver plated copper shields.
CAN bus signal issues?
CANBUS is a high speed network which requires high quality wiring in order to operate properly. As such, it is sensitive to improper wiring. The majority of CANBUS communication problems are caused by poor wiring, incorrect termination, or the use of multiple frequencies on the same bus.
CAN bus 120 Ohm termination?
A CAN Bus network must have a terminating resistor between CAN High and CAN Low for it to work correctly. For maximum range over long distances, the ideal termination is one 120 Ohm resistor at each end of the bus, but this is not critical over short distances.
Why do both ends of a can cable have to be terminated?
For high-speed/FD 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.
When is the termination of a bus irrelevant?
If your bus is shorter than one wavelength over 10, the termination is irrelevant (practically) since there is plenty of time for the reflections introduced from an impedance mismatch to die out. Length defined in wavelengths is a strange unit on first encounter.
Where is the termination resistor on a can cable?
For low-speed/fault-tolerant CAN, each device on the network needs a termination resistor for each data line: R(RTH) for CAN_H and R(RTL) for CAN_L. Unlike the high-speed CAN termination, low-speed CAN requires the termination to be on the transceiver rather than on the cable.
What causes the energy to return to the main CAN bus?
Generally, the unit impedance is 100 kOhm, resulting in a 100% reflection of the energy back to the main CAN bus, delayed by the propagation delay in the drop-line. This energy will return back to the main CAN bus with 0 phase shift. Alternatively, the EMC filter could cause a phase-shift in the reflected energy.