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TPS543820: Using in Marginal Condition

Kazuki Itoh
Genius 10820 points
Part Number: TPS543820

Tool/software:

Hi team,

My customer is considering to use TPS543820RPYR for high current rail below.

  • Vin: 12V
  • Vout: +0.85V
  • Iout: 6.5A (typ.) | 8.2A (max.)
  • Ripple voltage limitation: 20mVpp

This supplies FPGA. Should it be okay?

I think my customer should switch to higher current device like TPS56C231RNNR.

Best regards,

Kazuki Itoh

  • 0
    TI__Mastermind 23995 points

    You will need to know the inductor and part number and swithcing frequency. 

    Use equation 7 below to calculate ripple.

    Fsw is switching frequency

    Lo is inductance, check inductor datasheet and lower inductance using Lo vs current curve in datasheet.

    Ipeak eq 9 should be less than 11.7A based on the ec table, to avoid current limit

    Ivalley should be less than 9.4A based on the ec table, to avoid skipping hs fet turn on and current limit

    ILvalley =  Iout – Iripple/2                              

      

    Alternately, use can download and use POWERSTAGE-DESIGNER Design tool | TI.com

    Enter input, output votlage, switching frequency, inductor and output current values

    and click the inductor to show the peak and valley values

    Read min and max inductor current. 

    Regards

    David

  • 0 in reply to David_Daniels
    TI__Genius 10820 points

    Hi David, 

    With respect to the high-side and low-side current limit, yes, you need to calculate the ripple by using inductor value to make sure it doesn't exceed the current limit.

    But how about Iout? The maximum current 8.2A exceeds the recommended operating conditions.

    Could you let me know your thought?

    Best regards,

    Kazuki Itoh

  • +1 in reply to Kazuki Itoh
    TI__Mastermind 23995 points

    Itoh-san,

    Is the 8.2A output current, continuous for 100% of the operation or closer to 10%.     

    What are the power on hours.       8.2A is not much greater than 8A. 

    There are customers considering TPS543820 for >9A  (~10% of time) applications. 

    For that use case, electromigration was reviewed and considered good. 

    I do not have a concern about the 8.2A.    What do we need to do to convince customer.   

    Customer can use evm and change inductor so it can source an output current closer to the current limit to check performance.