V G wrote:
> I bought a 4.7 uH inductor but they only carried those with
> 1/2 watt rating. I bought it anyway.
>
> I'm wondering if the power rating on this inductor is sufficient for
> this chip supplying 1 Amp at 5 Volts from a 4.2 - 5.8 Volt supply.

It's impossible to tell based on just the inductance and the power rating o=
f
the inductor.  The important parameter of the inductor is its saturation
current.  That's the current at which the inductance drastically plummets
for higher current values.  In other words, it stops being a inductor and
looks primarily like a resistor, which has the value of it series
resistance.

The power rating comes from how much heat it can dissipate.  Ideal inductor=
s
can't dissipate power, so all the heat comes from the equivalent series
resistance.  If you know what that is, you can calculate the RMS current
that will produce the specified power dissipation.

The fact that your inductor came with a power rating instead of a saturatio=
n
current rating and the fact that it's only rated for 1/2 Watt makes me thin=
k
it's a RF choke.  Those are meant for RF applications where the impedences
are generally high and a few Ohms resistance in the inductor not a big deal=
..
For power applications the frequencies are lower, the currents high, the
impedences therefore lower, and the inductor resistance a important factor.

Coilcraft is pretty good about free samples in small quantities.  They make
all kinds of power inductors and specify them well.


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