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ISOW7841: Ok to power the isolated section with the non-isolated section off?

Derek
Mastermind 9802 points
Part Number: ISOW7841
Other Parts Discussed in Thread: ISO7841

Hello,

   As part of our testing we would like to test just the isolated section of circuitry with the rest of the board unpowered. So we would connect an external 5V supply to VISO, (connected to pin16 & pin10) and then GND from this external supply to pin 9 & 15. The other side of the chip (the non-isolated side) would be unpowered.

Is this ok? I tested it on one board and it worked fine but I wanted to ensure that we aren't going to damage the ISOW7841 somehow. 

Thanks,

Derek

  • 0
    TI__Expert 6955 points

    Derek,

    It's not part of normal operation for this device to have an external source of power being fed to Viso. In theory the internal rectifier should prevent damage as long as the voltage stayed under the abs max.

    Ideally you would would evaluate the ISO7841 with external power supplies if you just wanted to analyze the isolation portion. This is essentially the ISOW7841 without the integrated isolated DC/DC.

    Respectfully,

    Lucas

  • 0 in reply to Lucas Schulte9
    Mastermind 9802 points

    Thanks, we're trying to troubleshoot devices where the ISOW7841 is failing since we are seeing a very high number of part failures with the 9xxxxxx date code, as described in https://e2e.ti.com/support/isolation/f/1013/t/898586 

    When the part fails (which is most of the time) we're pulling it off and replacing it with a part with the 8xxxxxxx date code and those seem to be working. But I wanted to test the isolated side without removing the IC.

  • 0 in reply to Derek
    TI__Guru 55825 points

    Hi Derek,

    For troubleshooting purposes only, you can power the secondary/output side independently making sure the datasheet specs are not violated. Like Lucas mentioned, this is not recommended otherwise. Thanks.

    Regards,
    Koteshwar Rao