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TPS92641EVM: Current waveform confirmation

K.Shidara
Expert 3225 points
Part Number: TPS92641EVM
Other Parts Discussed in Thread: TPS92641, LM3409

Hi Team

My Customer is facing the issue so please advise below inquiry.

When an electronic load was connected to the output of the evaluation board of the TPS92641 and the operation was confirmed in CV mode, it could not be operated normally.Please tell us if there is a technique to make it work properly.

I tried to confirm the operation by connecting 19 bridge diodes in series to the output. The waveform is very dirty, is this normal?
Sorry to trouble you, but please check the waveform below.

Thanks

Best regards,

Shidara

  • 0
    TI__Mastermind 28655 points
    Hello,

    The waveform looks correct. Using an electronic load can have issues, these are current regulators with loop compensation. The electronic load does not behave like an LED string or diode string. It is best to use an LED load (or diode string) for testing. Some parts such as the LM3409 may not even start with an electronic load.

    UDIM goes high, it starts switching, wide pulse to get current back to regulation point then switching. UDIM goes low, TPS92641 turns off and has natural damped ringing when the switches open, this is normal.

    I would check to make sure your power source is solid and Vin at the EVM is not drooping (it looks like it is a little).

    Best Regards,
  • 0 in reply to Irwin Nederbragt
    TI__Expert 3225 points
    Hi Irwin-san
    Thanks for your reply.
    Waveform I sent is diode strings 's one. It isn't electric load.
    Is this normal?

    One more question, Are there any frequency limitation of UDIM and SDIM even though
    there is no description in datasheet?

    Thanks
    Best regards,
    Shidara
  • 0 in reply to K.Shidara
    TI__Mastermind 28655 points
    Hello Shidara,

    There are limitations on both. UDIM, the rise and fall of the inductor current and accuracy. SDIM, frequency beating with the switching frequency. These are design dependent, Vin, Vled, Fsw, inductor value, Iled, etc.

    Best Regards,