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LMR43620: step in VOUT waveform

Jane Ye
Expert 3320 points

Part Number: LMR43620

Hi team,

I am using LMR43620 for DCDC. I found that when I power up the 12V input , there will be a step on the output as I have shown. Could you please help to check with it? The yellow line is output 3.3V. image.png

  • +1
    TI__Guru* 84375 points

    Hello

    This is normal start-up.

    The first current pulse takes Vout up a little higher than the reference and switching stops until the reference voltage increases.

    Although it is hard to see, it appears in the data sheet image of start-up shown below.

    Thanks

  • 0
    TI__Expert 3320 points

    Hi Frank,

    Thanks for your reply. I have a follow up question:

    I am now using it to drive LED driver board. With the LED driver, I can see the waveform has a step of 300mV on some of the boards. Do you have any idea about this? The waveforms are attached. They are from 2 different boards with the same layout and test function.

    Best regards,

    Jane

  • 0 in reply to Jane Ye
    TI__Guru* 84375 points

    Hello

    It is hard to say.

    Maybe some residual voltage from the LED driver.

    Thanks