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ISOW1412: VISOOUT does not output

Part Number: ISOW1412

Dear team,

Would you please answer the following question?

Conditions VDD = VIO = 3.3V, VISOOUT = 3.3V(Expected)

Problem: VISOOUT does not output

Question: Do I need to set it sequentially to output VISOOUT?

I couldn't find it in the data sheet for that procedure.

Other settings can be disclosed, so please ask if necessary.

  • Hi,

    Sorry to hear about the issue and thanks for reaching out.

    Could you please confirm if you have connected VISOOUT to VISOIN either directly or through a ferrite bead? VIO and VISOIN need to be powered for the DC-DC converter in ISOW1412 to be in operation.

    Problem: VISOOUT does not output

    Could you please confirm what voltage do you see at VISOOUT? Is it close to 0V or do you see something else?

    Question: Do I need to set it sequentially to output VISOOUT?

    It would be sufficient to power both VDD and VIO at the same but if one supply is going to be available before the other, then I would recommend that first VIO be powered and then VDD.

    Look forward for your inputs, thanks.


    Regards,
    Koteshwar Rao

  • Thank you for your prompt response.

    > Could you please confirm if you have connected VISOOUT to VISOIN either directly or through a ferrite bead?

     It is directly.

    >  Is it close to 0V or do you see something else?

     It is just 0V.

    Best regards.

  • Hi,

    Thanks for your inputs. Could you please try testing a new device? This time please short VDD and VIO for the testing purpose only.
    Please do also share the schematic so that I can review to make sure there are no issues in the schematic. Thanks.


    Regards,
    Koteshwar Rao

  • Thank you for the instructions.

    I will hurry and send you the schematic and pattern diagram.

    Then, I Jumper VDD and VIO to make a short circuit.

    Best regards.Reply_210611.pdf

  • Dear team,

    Additional information.

    I tried the jumper, but no VISOOUT was output.

    Originally, as you can see, VDD and VIO are close.

    Best regards.

  • Hi,

    Thank you for sharing the schematic.
    I quickly reviewed the schematic and I see that the 0Ω resistor R3803 connects EN pin to GND1. This will disable the DC/DC converter and hence, no output will be generated at VISOOUT.

    Could you please confirm if R3803 is populated and if EN pin is connected to GND? If EN is connected to GND1, then could you please remove R3803 resistor and either connect EN pin to VDD or leave it floating, it has internal pull-up. Please do this test and let me know if you can see the output VISOOUT showing 3.3V.

    As additional feedback on schematic, I would recommend to keep another 10µF at VISOIN as this power pin is powering the RS-485 driver. This helps maintain a stable power to the RS-485 bus. Thanks.


    Regards,
    Koteshwar Rao

  • Hi,

    Please let me know your inputs to the information I have requested in my earlier post, thanks.


    Regards,
    Koteshwar Rao

  • Dear team,

    Thank you for your instruction.
    I misunderstood the operation of the EN pin.
    I'd like to try it right away.
    I will reply as soon as I try.

  • Hi,

    Thanks for your response. I will look forward to hear from you after you try testing with the modifications, thanks.


    Regards,
    Koteshwar Rao

  • Hi,

    I hope you get a chance to test the device soon.
    I will go ahead and mark this E2E post as closed. Once you have an update from the test, you can reply to this post with an update and if you were able to get everything working. This E2E post gets locked in 4 weeks, if that happens, you can create a new post by clicking on "Ask a related question". Thanks.


    Regards,
    Koteshwar Rao

  • Dear team,

    Attempts were made on EN pins.
    There was no problem, and VISOOUT was output.
    Thank you very much.