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DAC8750: DAC8750 getting damaged frequently

Nav
Prodigy 140 points
Part Number: DAC8750

Hi,

We have designed an application for isolated current output based on the DAC8750. We have had frequent incidents of the DAC8750 getting damaged after being operational for a few hours. Only on replacing it with a new chip the application starts working again. We need help from TI in analyzing our application and help us find any fault in our design. Please provide a support email where I can send the details as the information cannot be posted publicly.

  • 0
    TI__Guru* 93465 points

    Nav,


    I've sent you a friend request on E2E. Using that, you should be able to send me information through the E2E messaging utility.

    At this point, it's a bit hard to speculate what might be wrong, but there have been issues with powering up the device with transients faster than 1V/ns speeds. You might see this in applications where the supplies are "hot swapped", where the supply comes up from by attaching a board to the power with low ESR charged capacitances. Other than that supply fast ramp and other over-voltage faults, I don't know of any failure mechanisms with the device in normal operation.

    Again, once you find my friend request, you should be able to message me. You'll need to log into E2E and use the message icon at the upper right of your browser.


    Joseph Wu

  • 0 in reply to Joseph Wu
    Prodigy 140 points

    Hi Joseph,

    Thanks for the quick response. I've done as you said but I cannot initiate any message. Can you please initiate from your end? I'll respond to that.

  • 0 in reply to Nav
    TI__Guru* 93465 points

    Nav, 

    I checked and I can't find you in the system. It could be that there's some delay before this functionality enabled in the E2E system. 

    Normally you would go to the message icon as shown here:

    After clicking on it, select "New message"

    Then you would click "New" and then "Find recipients...". You would then enter my name and you should be able to send a message if we are friended in the E2E system. 

    Even if you can't send schematics, you should be able to send me information about the nature of the operation and how it is tested when you see failures. 

    Note, I'm about to go offline and can look at your comments tomorrow.

    Joseph Wu

  • 0 in reply to Joseph Wu
    Prodigy 140 points

    Likewise, I'm unable to locate your name in recipient field as well. That's weird. I hope we can arrive at some solution. Meanwhile here is some information that I can provide:

    1) I'm quite sure that the power supply ramp would be nowhere even close to 1V/ns. It is derived from a small (1W) DC-DC converter with 24V DC regulated output. But we will probe it and confirm soon.

    2) The board powers up and the DAC operates just fine for a while. It fails even when it is kept powered ON without power cycles.

    3) The failure mode is such that current output is stuck at ~28mA always & doesn't respond to DAC data register changes.

    4) The digital (SPI) communication is intact. We can change registers and reading it back gives the written values.

    5) Status register doesn't show any errors.

    6) External NPN transistor is used to off load power dissipation from the DAC.

    7) No perceivable overheating of any of the components.

    8) Measurement is done through direct connection of ammeter at output terminals.

    Any pointers?

  • 0 in reply to Nav
    TI__Guru* 93465 points

    Nav,

    I was able to figure out how to send the message by hovering the mouse over your name in the post. This allows for sending a message. 

    I read through your last post and I don't see anything that would be unusual. I'll wait for you to respond with a schematic in your reply message and we can go from there.

    Joseph Wu