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Inductor Selection for a TPS63000 in Buck Mode

Greg Pastalan
Prodigy 50 points
Other Parts Discussed in Thread: TPS63000

Hello:

 

I have question regarding the correct selection of the inductor for a TPS63000 when in Buck mode, converting +5V to +3.3V.  The data sheet describes a selection procedure when the input voltage source is a battery with a possible voltage min / max of 2.5V to 4.2V, however in my application I will be using a dc power supply at 5V.  The equations in the data sheet used for selecting the inductor value are no longer applicable.  Are there any special considerations I need to make or can I proceed with the recommended inductor value of 2.2uH?

 

Thank you.

  • 0
    TI__Guru**** 150950 points

    Yes, you can always use the recommended value of 2.2uH.  Doing this may limit your available output current under some conditions.

    Since you will only be operating in step down mode, you would use equation 3 which gives a value of 3uH.  So, >3uH is recommended but 2.2uH is ok too.  Under your conditions, the 2.2uH inductor will give more inductor ripple which may limit the available output current.  How much output current do you need?

    Make sure your effective output cap meets the 5 times L capacitance requirement of equation 7.  The effective capacitance is the nominal capacitance minus the DC bias loss.  For 3.3V on 6.3V caps, this is estimated at a 50% reduction.