I have a device with a SNx5HVD251 CAN transceiver. I opened the datashett and read the following parameter:

IOS(SS) - Short-circuit steady-state output current

Below are two images of the datasheet that I put together here:

enter image description here

I didn't understood the relevance of this parameter or what it means.

1)For example, if I have VCANL at 12 V, CANH Open . It means that the current over CANL line will be at maximum of 200mA ? Or, it means that CANL line can support at maximum of 200mA ?

2)The CAN line will be passing through a relay. (The relay will not switch during communication, but the CAN line need to pass through it). So, how relevant is to take this value of current into account when I need to specify my componentes ? A relay with less than 200mA is much more cheaper, so I need to know the relevance of this parameter.


1 Answer 1


Those are worst case short circuit currents. If something breaks and the CANL pin gets directly connected to 12V supply voltage, maximum of 200mA can flow when it tries to drive it low. And the other case, if CANH gets connected to -7V, max 200mA can flow. Wires must handle at least this current. Surely most small signal relays can switch 1 or 2 amps, 200mA is nothing.

  • \$\begingroup\$ Ok, I understood. But the diference of price between a SSR that can handle 100mA and other that can handle more than 200mA is almost the double. I will need thousands of SSRs, so in the end, this diference is considerable. Because of this I'm so concerned with this parameter \$\endgroup\$
    – Daniel
    Jan 15, 2020 at 3:38
  • 1
    \$\begingroup\$ Solid state relays are generally used to switch power on and off quite slowly. Are you sure they can be used to pass 1 megabit data signals reliably? Which SSR part number would this be? What is your CAN bus data rate? \$\endgroup\$
    – Justme
    Jan 15, 2020 at 5:39
  • \$\begingroup\$ I didn't find nothing that could disrupt the communication yet, but is possible. The data rate is up to 1Mb/s. I'm in doubt between TLP241A and TLP175A \$\endgroup\$
    – Daniel
    Jan 15, 2020 at 11:34

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