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TPSM82480EVM-002: Start Up questions

David C
Expert 3350 points
Part Number: TPSM82480EVM-002

Hello,

I am currently having trouble getting this evaluation board to function.  I have attached a 3.3 volt supply with a current limit of 200 milli-amps to the input and all the evaluation board does is load my attached power supply down into a current limit mode.  A resistance measurement across the input terminal screws measures only 0.4 ohms which does not seem right at all and would explain why my input  power supply immediately goes into a current limit mode.  Is there something that I am doing wrong here or did I just receive a defective evaluation board?  Any help will be appreciated.

Regards,

David

  • 0
    TI__Guru*** 142680 points
    Hi David,

    200 mA sounds really low for a 6A device. Can you increase it?

    As well, some input supplies may not be able to accurately limit their current to 200 mA and may limit it to lower values or will limit it to a non-constant value.

    If you want to debug your input supply, please post a waveform of Vin, Vout, and input current.
  • 0 in reply to Chris Glaser
    TI__Guru*** 142680 points
    Hi David,

    Were you able to retest with a higher input current limit or get some waveforms?
  • 0 in reply to Chris Glaser
    TI__Expert 3350 points
    Thanks for getting back to me. No matter where I set the current limit on my input power supply it immediately goes into a current limit mode when I connect it to the blue input screws on the evaluation board. As I mentioned earlier the resistance across the two input screws measures only .4 ohms, which seems way too low to me. Is it possible that one of the inputs capacitors on the evaluation board is shorted? Are these evaluation boards tested before being shipped out? Should I try to remove the input capacitors on the evaluation board to see if one of them is shorted?
  • 0 in reply to David C
    TI__Guru*** 142680 points
    Ah, thanks for clarifying.

    Does the IC get hot when the current limit is at 1A? Can you send a waveform of Vin at 1 msec/div? Does the EN jumper position have any effect? Can you send a photo of your test setup and a close up of the EVM?

    Yes, each EVM should be powered on and tested for functionality. You could order another one and work with the TI Store to return the first one, if it is indeed broken. The above questions can help confirm this possibility.