PCB Routing of CANH and CANL

by VanGo   Last Updated September 11, 2019 17:25 PM

Continuation from an earlier question: Current Consumption of CANbus (CANH and CANL)

I understand how to specify my power supply for multiple CAN transceivers but I am now wondering about the details for routing CANH and CANL lines on the actual PCB.

  1. It seems to me like most of the supply current is being used by the RX/TX lines and not alot is used to drive the actual CANH/CANL lines - i wasn't able to find anything about the current draw of CANH/CANL in the datasheet of the transceiver I was looking to use. How do I find the current draw of the CANH/CANL lines so that I can calculate the appropriate trace thickness on the PCB ?

  2. I sometimes see CAN referred to as having a characteristic impedance of 120 Ohms but others refer to it as having a differential impedance of 120 Ohms. How do I route CANH/CANL on my PCB? Should it be routed as a edge coupled microstrip with a differential impedance of 120 ohm - if so how is this differential impedance maintained during the twisted pair cabling since there is no reference plane?

I came across this similar question earlier but the answers seem to be that it was a non-issue. Not sure if this is still the case with a bus length of 1.5m and ~50 nodes.

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