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TPS54329: How to tune ripple noise down on TPS54329DDAR (12 V to 2.5V).

Randy Fung1
Prodigy 40 points
Part Number: TPS54329

Part number used: "TPS54329DDAR"

Function 12V to 2.5V step down. Intended current about 150 to 200 mA.

We did not install the ASIC chip on board. (NO"VDDH Supply" chip loaded).

We have about 13 of 1uF near the load and 4 x 10uF at the out put of the regulator. 

Probing the 2.5V rail "VCC_VDDH" on Ac coupling and noticed it has about 15 mVpp ripple and 20 mVpp spike noise.

How can reduce the ripple and the spike?

Thank you.

Randy

  • 0
    TI__Prodigy 450 points

    Hi Randy,

    What type and model of Cout capacitors do you use?  Vout ripple is inversely proportional to the Cout values, so you can try adding 1 more 10uF cap.

    regards,

    jenson

  • 0 in reply to Jenson Lam
    Prodigy 40 points

    Hi Jensen,

    General Purpose Ceramic cap.

    C0603X5R250-106MNP. I used 4 x of this. General data sheet indicated < 10 mohm on ESR

    I also have 14 x 1uF (C0402X5R250-105KNP) at the ASIC chip.

    I already have the board respin. No way to add more caps to the line. 

    What do you suggest? Increase cap value?

    Thanks.

    Randy

  • 0 in reply to Randy Fung1
    TI__Prodigy 450 points

    Hi Randy,

    Vout ripple is determined by Iripple, fsw, and Cout value.  Since fsw cannot be adjusted, you need to either (1) reduce you inductor ripple current (Iripple) or (2) increase size of the Cout.  

    Taking consideration of the DC bias derating of your cap, it's around 8.311uF for each cap. Therefore, you have 33.24uF at the Cout.  The recommended Cout for 2.5V output is between 22uF - 68uF.  Therefore, you may try to increase your Cout.

    regards,

    jenson