[gta02-core] ECN0010 re-opened (was Re: More audio considerations)
werner at openmoko.org
Thu Nov 12 00:26:26 CET 2009
> Also, let's try to use IO_3V3 then. As a precaution, I'd add a 0R
> before LDO34IN, so that it can be reworked to use Vsys in case
> there are problems.
Joerg raised a few good points against this plan. He's too shy to
post, so here's my summary:
- current surges would propagate from CODEC_whatever to IO_3V3,
possibly causing trouble,
- inrush current on LDO3/4 would be drawn from the IO_3V3 capacitors,
possibly causing trouble as well,
- last but not least, while a DC-DC converter is generally more
efficient than an LDO, this seems to be a case where they're
pretty much on par: if Vbat is 3.9 V and we burn 0.6 V in the LDO
to reach 3.3 V, that's 85% efficiency, just about the same we'd
expect for the DC-DC converter.
I've removed the section and added a rationale why it's not a great
idea to use IO_3V3 in this case.
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