TCAN1042-Q1: What is the longest distance the CAN signal communication can support?

Felix,

1. A good "rule of thumb" number that I see a lot is 1Mbps is limited to roughly 40 meters of cable. So going to a faster data rate will shorten that distance, and going with a slower data rate will increase that distance.
2. The bus distance limitation is dependent on the propagation delay of the message traveling from it's point of generation, all the way down thebus cable, and back to it's original point of generation. This travel time is affected by the transceiver delay, controller delay (though this isnegligible in most cases), cable delay, and any delay associated with devices on the bus such as common-mode chokes, ESD protection diodes,filter capacitors, etc. The distance limitation doesn't have to do with the supply voltage, however, some transceivers has shorter loop delay thanothers. This is found in the datasheet under the timing characteristics, the parameter is called tPROP(loop1) and tPROP(loop2).

The reason this delay is crucial to CAN communication is due to the arbitration portion of the communication determining priority of the messages and which controller gets to control the bus at any given time. Each bit of a message has to travel from the controller, through the transceiver, down the length of the cable and back within 75-80% of the bit time in order for the original controller to properly determine message priority and if it has won priority to control the bus.

TI also has a general CAN physical layer requirements application note, found here. CAN bus distance vs. signaling rate is explained here as well.

Please let me know if you have any other questions.

Regards,