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LM25576 and lm25117 have big spikes

Zeev Gerber
Intellectual 500 points
Other Parts Discussed in Thread: LM25117, LM25576

Functionality:

Input : 24V

Output:

24V/2A,

5V/5A (LM25117)

3.3V/5A (LM25117)

-5V/2A (LM25576)

 

The control loops is stable. 

The problem is spikes in the switching frequency of the LM25117 (250 Khz)

The spikes are about 500 mv on the 5V and 3.3V and 1000mv on the -5V

Pls. advise

I will Attach the current schematic of the card when I know who to do it.

 

  • 0
    TI__Guru 58761 points

    Hi

    Please capture the spikes for more information.  2~3us /div  scale is preferred.

    Regards,

     

  • 0 in reply to EricLee
    Intellectual 500 points

    Hi,

    This component (lm25576) was recommended by NSC when I starting the design and search for DC2DC to make -5V/2A from 24V input.

    In the DS NSC have application example of inverting and I also simulate it in the webench.

    When I try to make simulation again today I see the webench didn’t run and have message the LM25576 have unstable FET ehavior in this condition (-5V/2A from 24V input).

    Pls. advise if the LM25576 could work properly when making -5V/2A from 24V input.

    In addition could you send me how to attach file?

    Regards

    Zeev Gerber

  • 0 in reply to Zeev Gerber
    TI__Guru 58761 points

    Hi

    Would you please capture the spike waveforms (LM25117's) ? 2~3us /div  scale is preferred. I supports LM25117.

    Regards,