• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 63 subscribers
  • Views 269 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS544C20: Inductance selection

Mason Noh
Expert 2490 points
Part Number:

Hi TI experts,

I have designed the power board with TPS544C20. I refer to webench tool.

https://webench.ti.com/power-designer/switching-regulator/customize/752?AppType=None&O1I=30.0&O1V=3.3&VinMax=12&VinMin=12&base_pn=TPS544C20&lang_chosen=en_US&op_TA=30&optfactor=3&origin=ti_search&refpage=http:%2F%2Fwww.ti.com%2Fsitesearch%2Fdocs%2Funiversalsearch.tsp

Input: 12Vdc, Output: 3.3V/30A

It is working well with 700nH inductance. But when I changed to 1.8uH, it is not working. no switching, no output.

Could you explain the reason?

Inductor part No.

700nH: CDEP-147NP-0R7MC-95 (sumida)

1.8uH: CDEP-147NP-1R8MC-73 

And I have a audible noise issue with 700nH inductor. Do you have any debugging point?

  • 0
    Intellectual 470 points

    Mason Noh said:

    Part Number: TPS544C20

    Hi TI experts,

    I have designed the power board with TPS544C20. I refer to webench tool.

    Input: 12Vdc, Output: 3.3V/30A

    It is working well with 700nH inductance. But when I changed to 1.8uH, it is not working. no switching, no output. A higher inductance value means  a lower cutoff frequency of the LC filter leading to a lower bandwidth. Too low a bandwidth can cause issues with startup. Try re-calculating the compensation network values to keep the loop in the stable region.

    Could you explain the reason?

    Inductor part No.

    700nH: CDEP-147NP-0R7MC-95 (sumida)

    1.8uH: CDEP-147NP-1R8MC-73 

    And I have a audible noise issue with 700nH inductor. Do you have any debugging point? Your IC is running into Hiccup Mode. In Hiccup mode, your effective switching frequency becomes low enough to lie in the audible region and is causing you trouble.

    Thanks,

    Avish