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Inductor for LM22680

Chaw Chen Song
Prodigy 20 points
Other Parts Discussed in Thread: LM22680

Hi there,

I am current design a DC-DC supply for my design, using LM22680.

The problem now is from the design software, it recommand to use the inductor of 15uH at 40milliohm.

In the market is hard to find the inductor with this spec. What will happen to my design, output current or valtage if I use a 15uH with different resistant.

Thanks in advance, all feedback are welcome.

ChawCS

  • 0
    TI__Guru**** 191445 points

    For the LM22680 the inductor value is chosen so that the ac ripple current is 30% of the output current.  This is a very typical rule of thumb for buck converters.  It is possible to vary  a little bit.  You may specify 20 or 25 % ripple and that will yield a larger inductor value.  For your question about DCR, for a given inductor value, the DCR is mostly determined by the wire cross section area used in the windings.  Lower DCR inductors use thicker wire with less resistance.  Higher DCR uses thinner wire.  The lower DCR will have better efficeincy and higher current ratiing for the inductor.  Higher DCR will decrease efficiency and will have lower current rating.  So you can always use a lower DCR inductor, it may just have a larger physical size.  You can use a higher DCR so long as it still meets your current rating requirements and you don't mind slightly lower efficiency.

  • 0 in reply to JohnTucker
    Prodigy 20 points

    Thanks John,

    Unless now I know which DCR value should I use.