I have to isolate the signals CAN-High and CAN-Low on a CAN bus.

Is there an isolated CAN repeater (something like IXXAT's CAN-Repeater - 110 × 75 × 22 mm) which would be possible to mount on a board?

I mean a component CMS or through hole that I could solder on a printed circuitry. Or at least something much smaller than the one I posted.

  • \$\begingroup\$ I don't really know for the isolation part but as a repeater, you can use the AMIS-42770 (link to the datasheet : onsemi.com/pub_link/Collateral/AMIS-42770-D.PDF). It's a CAN transceiver with two bus lines which can act as a CAN bus extender/repeater without the need of an external microcontroller. With this chip and the previous answers, you can probably build something. \$\endgroup\$ – thb Feb 20 '14 at 18:39
  • \$\begingroup\$ What is CMS in this context? \$\endgroup\$ – Peter Mortensen Feb 21 '14 at 20:37
  • \$\begingroup\$ Why is this question not fitting the rules? Even if it's seeking for a recommendation it can help anyone who want to build a repeater CAN on a board. And moreover if you can look at the different answer and comment you can see it can also avoid some easy mistakes. \$\endgroup\$ – damien Feb 24 '14 at 10:52

Try the following: -

enter image description here

Here is the link to a useful ADI document.

  • \$\begingroup\$ Thank you but this file describe an isolation of TX and RX after the transceiver. Wha t I want is an isolation directly on CANH and CANL. This is why I need an isolated repeater. \$\endgroup\$ – damien Feb 20 '14 at 16:23
  • \$\begingroup\$ @damien: The CANH and CANL lines are bi-directional, so isolating them will be difficult at best. It makes more sense to isolate the uni-directional lines on the controller side of the transceiver chip. Yes, this means providing a little power on the isolated side. \$\endgroup\$ – Olin Lathrop Feb 20 '14 at 16:45
  • \$\begingroup\$ Yes I know they are bidirectional this is why I would need a repeater, the thing is I will not have the lines TX and RX on the board. Because the CAN is just passing through the board I want to isolate \$\endgroup\$ – damien Feb 20 '14 at 16:52
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    \$\begingroup\$ The most effective way for this to work is isolation on Tx and Rx. You can use two CAN transceivers to make this work then it's transparent to the bus. Sorry I didn't mention that. \$\endgroup\$ – Andy aka Feb 20 '14 at 17:16

I think what you want is an ISO1050:



It's an isolated transceiver. One side connects to the processor CANTX and CANRX, and the other side connects to the bus CANH and CANL. Two isolation voltage levels available. Only surface-mount, no through-hole available, but the 8-pin variant is a DIP8 with bent legs, so it's easy enough to solder by hand.

Of course, it sounds like you just want to isolate the bus itself, and not feed data to a processor. But I think you should be able to put two of these devices back-to-back. Tie the CANTX from each to the CANRX on the other. I haven't tried it, but with appropriate power supplies, it sounds like it should work.

  • \$\begingroup\$ I think the solution of putting two transceivers "back to back" is not functionnal. Let's say you have T1 and T2: TX of T1 on RX of T2 and TX of T on RX of T1. If T1 sees a bit dominant on his CANH/CANL it will put a 0 on TX and T2 will put a dominant bit on his CANH/CANL. BUT then T2 will read his own dominant bit and put a 0 on his TX, T1 will put a dominant bit on his own CANH/CANL and then the bus is blocked. When a dominant bit is put on one of the bus it will stay dominant for ever. \$\endgroup\$ – damien Feb 24 '14 at 10:50

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