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LM5140-Q1: Abnormal phase waveform

Roy Hsu
Genius 9390 points
Part Number: LM5140-Q1

Hi Team,

My customer uses the LM5140-Q1 in a 24V -> 12V application and observed a strange waveform at the switching node.

Do you know what the cause might be? I will send you the schematic via email.

Thanks!

Roy Hsu

  • 0
    TI__Mastermind 25590 points
    Roy,

    This looks like subharmonic oscillation. This is common in current-mode converters/controllers at duty cycles above 50%. Check the compensation in WEBENCH to make sure this is compensated properly.

    Please also check the small pulse off-time. I want to make sure it's >45ns (Ton_min) so we know the IC is not faulting.

    Thanks,
    -Sam