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TPS548D22: TPS548D22 switching frequency selection for 5Vout

Mark Chen52
Expert 7895 points
Part Number: TPS548D22

Hi ,

Could you help to know have any risk of customer design spec as below?

Vin=12V,

Vout=5V

Itdc=16A

Ipeak=32.5A

Fsw=875kHz.

L=0.47uH.

because check with  WEBENCH for customer design, only 425kHz switching frequency available, but for customer real design the Fsw set to 875kHz.

 i think maybe have thermal concern, so i would like to double check with you for customer design if that's ok or not.

kindly let me know if you need more information.

thanks,

Mark

  • 0
    TI__Expert 7895 points

    Hi, 

    Does anyone could help on this?

    Thanks,

    Mark 

  • 0 in reply to Mark Chen52
    TI__Guru**** 191445 points

    Mark,

    It appears to be thermal.  I can get 650 kHz.  Lowering to 10 A allows higher frequency options.  Webench tends to be conservative.  You may be able to get higher frequency with careful PCB design.  The conservative approach would suggest to lower the frequency and increase the inductor value.

  • 0
    TI__Guru 56815 points

    Mark,

    WeBench is limiting the switching frequency options due to thermal concerns of a 12V to 5V converter at 32A.  As John notes, WeBench is conservative in its estimate of temperature rise and heat dissipation capabilities, but exact capabilities will depend on ambient temperature, PCB design, especially how much copper is available within the board to spread the heat out from the ground connected thermal pad on the TPS548D22 package.

    If the 32.5A peak current load is long enough in duration that the design needs to be able to safely operate at that current for temperature reasons (several seconds) I would not recommend operating 875kHz.

    What is the application's worst case (highest) ambient air temperature?

    What is the application's worst case (minimum) forced airflow?

    Does the application use a multi-layer PCB with several dedicated ground layers?

    What is the worst case (highest) RMS current, averaged over several seconds of operation?

  • 0 in reply to Peter James Miller
    TI__Expert 7895 points

    Hi Peter,

    To Confirm with Customer working on 32.5A of output current is very short time and this is multi-layer board. 

    so should be have no thermal concern.