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LM5145: LM5145 EVM Output Capacitor Ripple Current

Wenhao Wu
Genius 9046 points
Part Number: LM5145
Other Parts Discussed in Thread: LM5141,

Hi Experts!

When using LM5145 EVM, its output ripple has a platform, which is pretty weird, and it also exists in LM5141. Therefore my question is what is the cause of this platform?

Green line is output ripple, in which ripple caused by ESL, ESR and C itself can be clearly seen;

Yellow line is VIN;

Purple line is Inductor Current;


Thank you very much! 

Wenhao

 

  • 0
    TI__Mastermind 25590 points
    Wenhao,

    My best guess would be some resonance in the circuit due to component selection and/or layout. We see a very stable inductor current waveform so the FETs are behaving properly. And the IC doesn't have any other capability to change the output voltage, especially at a frequency ~2x Fsw.

    You could do some tests to confirm. You can add/remove different types of output caps in different places. You could change the frequency of the controller. You could try a different inductor.

    -Sam
  • 0 in reply to Samuel Jaffe
    TI__Genius 9046 points
    Ok, i will try it tmrw! Thank you!