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TPS54295: Feed forward capacitance

Hirotaka Matsumoto
Guru 27585 points
Part Number: TPS54295

Hi all

Would you mind if we ask TPS54295?

Our customer would like to use TPS54295 with Cff=1000pF in order to prevent coil vaibration.
(It depends on load, inductance and the board layout.)
There is the difference between recomendation value on the datasheet and Cff=1000pF.
In this case, might it occur occilation?
About DCAP2 topology, we assume that it can simulate exactly using FRA.
Therefore, could you let us know?

Kind regards,

Hirotaka Matsumoto

  • 0
    TI__Mastermind 18510 points
    Hi,
    Sorry don't fully get your mean about "with Cff=1000pF in order to prevent coil vibration"
    Cff is mainly used for Phase boost or transient performance improvement, as 54295 recommendation value in table 2, CFF is suggested <22pf or not stuff, and also follow my experience, Cff =1nf is exactly too big here, might cause loop unstable.
    And Yes, if want to check loop, you can test with FRA meter.
  • 0 in reply to Yuchang Zhang
    Guru 27585 points

    Yuchang san

    CFF is suggested <22pf or not stuff, and also follow my experience, Cff =1nf is exactly too big here, might cause loop unstable.
    ->Yes, we think so too.However our customer told us there is no coil vibration in case of Cff=1nf.
        In case of 22pF, it occurs coil vibration.
        So, we also recognize that it is relation to transient performance improvement only.
        Ok, we will ask our csutomer that they have another problems.

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Hirotaka Matsumoto
    TI__Genius 15135 points

    Hi, Matsumoto

    Confirm with you:

    What is the meaning of "coil vibration" ?

    Does it mean the audible sound generated by coil vibration? could you send us the schematic for reviewing?

  • 0 in reply to Zhao Ma
    Guru 27585 points

    Zhao san


    Does it mean the audible sound generated by coil vibration?
    ->Yes, that is audible sound generated by coil vibration.

    We would like to send you schematic using private message on E2E, so could you accept friend ship on E2E?
    (The schematic might contain customer's confidential contents.)

    Kind regards,

    Hirotaka Matsumoto