• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 12 subscribers
  • Views 494 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ISO1044: Does the CAN- bus fault protection also work when you bypass the galvanic isolation?

jan stappers
Prodigy 160 points
Part Number: ISO1044


Hi,

We are a slave device in a CAN-bus network, sometimes when the master shuts off the bus network, then the voltages on CAN-H/L will go up to 40V and remains there, because for that reason we want to use the ISO1044 because the CAN-bus pins might go up to 40V in certain conditions.

So we were thinking, if we connect both GND's together and both VCC's, so that they work on our GND and VCC that is also used by our microcontroller, will the 40V protection on CAN-H/L still work?

Or is there a better solution to protect us from this. We only have our main power and cannot use external power from the master to feed the other side of the CAN-isolator (we only have GND coming from the master). so somehow we need to generate this power on our own.

Best regards,

Jan

  • 0
    TI__Intellectual 1960 points

    Hi Jan:

    Thanks for posting your question on E2E.

    ISO1044 CAN bus pins don't rely on the isolation barrier to protect against +/-58V (absolute maximum rating of the bus pins) with respect to GND2. You may connect both GND's together and both VCC's and 40V on the CAN bus pins would not damage the device.

    Alternatively, you may use TCAN1044 if galvanic isolation is not needed in your application.

    Regards,

    Dushmantha

  • 0 in reply to Dushmantha Rajapaksha
    Prodigy 160 points

    Hi Dushmantha,

    Thank you for your answer, this helps us a lot!

    Is there a certain time limit for this protection, or can the 40V be on CAN-H/-L for an undefined length of time?

    Best regards,

    Jan

  • 0 in reply to jan stappers
    TI__Intellectual 1960 points

    Hi Jan:

    CAN bus pins can withstand 40V for short period of time; for example during a fault condition like short to supply. However, as stated in the datasheet Absolute Maximum Ratings table footnote, exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

    Regards,

    Dushmantha