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ISO7721: FDR

Part Number: ISO7721

Hi,

I'm new to the ISO7721 device and have recently incorporated it in our design. We run a serial UART interface through this device.

Unfortunately it doesnt seem to be working. I see the data at the input pins but it does show up at the output side. e.g. pin 3 in TXD from MCU where pin 6 is the ouput. I see data at pin 3 but not at pin 6.

The voltage supply is fine within the range. What am I missing?

Appreciate you help!

Thanks,

Arvind

  • Hi Arvind,

    What do you see between pin 6 and GND2? Is it constantly high or low or maybe variable?

    Alex.
  • In reply to Alex Ballantyne:

    Hi Arvind,

    In addition to Alex questions, could you please take out the non-working sample and test it separately (maybe on EVM) by manually applying inputs while monitoring outputs? This rules out if the samples is already damaged due to handling or other reasons.

    Did you try testing more than one sample on the same board? Do you see all of them not working?


    Regards,
    Koteshwar Rao
  • Hi Arvind,

    Some sanity check questions/comments to add to the other posts. (Based on your description, it looks like you are using the 8D package/pinout)

    1) What are you using to generate the isolated power supply for the secondary side (Vcc2, GNd2) ? To double check what you mentioned in the original post, are *both* supplies healthy and in normal range?
    2) Alex's comment below is important in the sense that if there is something wrong, then the output can go into failsafe mode (depending on part #, it can be failsafe high or failsafe low). In other words, it can be a static high or low and not be responding to the input if this is the case.
    3) For debug only: if you attempt to send data on pin 7, then do you see an output on pin 2? ( testing out the reverse channel on the same chip)
    4) Do you have a simplified schematic/block diagram that you can share?

    Regards,
    Abhi

  • In reply to Abhi Aarey:

    Hi Arvind,

    Since this thread has been open without any activity, I am closing this thread assuming you issue with ISO7721 is addressed. If you still see a problem, please respond back and we can help you address the issue you are facing. Thank you.


    Regards,
    Koteshwar Rao
  • In reply to Koteshwar Rao:

    Thank guys for trying to help and apologies for responding sooner. We resolved this by adding pullups on the ISO side. Our interface is working fine after adding the pullups.

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