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Question on TPS54310 output inductor

Anonymous
Anonymous
Other Parts Discussed in Thread: TPS54310

Hi,

 

I would like to ask a question on TPS54310.

 

In Spectrumdigital’s EVM6437 schematics, I found that different inductor values (3.3uH and 2.7uH) are used for different output voltage (3.3V and 1.8V). Is there any particular reason for choosing such different values?

 

More specifically, is the correct value of inductor an exact value, or a range that any inductance falls within it could work? Could I used either 3.3uH or 2.7uH for both {3.3V and 1.8V} output?

 

 

 

 

Thanks,

Zheng

 

  • 0
    TI__Guru**** 191445 points

    I do not know the source of your schematic.  i can tell you that it is not an officially supported "EVM".  To answer your general question:

    The inductor minimum value is typically calculated by:  L = (Vout/Vin) * ((Vin-Vout)/(Iout*Fsw*Kind)) where Kind is the percentage of ripple current relative to the output current.  The rule of thumb is to use 0.2 - 0.3 for Kind, but you can go a little lower or higher depending on how much ripple current you can tolerate.  All else being equal, the difference in inductor value for 3.3 V and 1.8 V output and 5 V input is about 2.5%.  You should be able to use the same value if the switching frequency and output current are the same.

  • Anonymous
    0 Anonymous in reply to JohnTucker

    Dear John,

    I see it, thanks very much for the timely answer.

    Zheng