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TPS54295: Cff capacitance and L=1.0uH in case of Vout=3.3V

Hirotaka Matsumoto
Guru 27585 points
Part Number: TPS54295

Hi all

Would you mind if we ask TPS54295?

<Question1>
According to adding Cff capacitance, is it possible to decrease Vout's ripple voltage?
(Is Cff capacitance effective to decrease Vout's ripple voltage?)

<Question2>
In case of Vout=3.3V(Vin=9V), is it possible to decrease the L value from 2.2uH to 1.0uH?

Kind regards,

Hirotaka Matsumoto

  • 0
    TI__Guru**** 191445 points
    I do not support TPS54295 directly, but I do have some familiarity with it. I think the support team is on holiday now, so I will give you my opinion.
    1. Cff does not really affect the output voltage ripple. It is used to boost the phase margin in the overall loop. In any case, the output voltage ripple should be very low with ceramic output capacitors.
    2. You can possibly try 1 uH for your design. The output L and C values of Table 2 in the datasheet are chosen for stability and are recommended. However the change from 2.2 uH to 1 uH is not that great. If you do make that change I would recommend using an output capacitance total on the higher side of the range, towards 68 uF so as to keep the LC resonant frequency inside the recommended range.