[gta02-core] ECN0044: Current rating of backlight LED inductor (L1704)

Álvaro Lopes alvieboy at alvie.com
Fri Apr 2 14:23:59 CEST 2010

Werner Almesberger wrote:
> We have a new ECN: the inductor (L1704) of the boost converter feeding
> the backlight LED has an odd specification that makes it hard to source.
> We can either lower the current rating (see the ECN for why this should
> be okay) or increase the footprint (which would also lower the
> resistance and save a bit of power.)
> I've tentatively changed the current rating of L1704 to 600 mA to let
> the BOM system pick up a suitable part.
> Further details in
> http://svn.openmoko.org/trunk/gta02-core/docs/ecn/ecn0044.txt

Not sure about this one. Point is you'll have peak currents in inductor which are probably diverted to ground by capacitance in circuit components, and not
necessarily trigger the over-current protection. Those peaks might not hurt the inductor at all, even if its current is higher than its rating, due to their
transient characteristic.

But, I'd go for 1210 package. It's better be on the safe side, and we ought to have enough room for it. OR, we can (can we?) lay out both, use the smaller one,
and then if we run into problems, do a little of SMD soldering magic.


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