> ... LTC3112 ...

Yes - that's another nice IC

            http://cds.linear.com/docs/Datasheet/3112f.pdf

Arguably even better than your last choice.
Importantly also has load disconnect, which matters when you have Vin >
Vout.
(Handled by the synchronous output stage.)

The LTC3112 has the great advantage that, with a little care, you can use i=
t
to charge your iPod etc from a 12V supply if you wish to. eg auto battery o=
r
cigarette lighter. If you add this option an auto environment rated LDO at
the 12V input would be "really wise" [tm].

For extra points you could also charge the NimH pack from the 12V
source.using the LTC3112.

For double extra points - 12V into charge internal  NimH AND iPhone
simultaneously :-).


And for basic NimH to iPhone use, almost as efficient as a linear supply
with 5 cells :-).

Linear:
Assuming 5V out.
5 cells at 1.0V cell =3D 100%. (slightly hard.)
5 cells at 1.05V =3D 95%
at 1.1 V =3D 91%
At 1.2 V =3D 83%
At 1.25V (not for long) 80%.

Note that this is the actual cell terminal voltage - all wiring, connectors
switches etc are included in the losses.

NOT as good a a nice buck converter - but close in efficiency.

If you use 6 cells you can use a soely buck converter - but unlikely to get
better than the LTC3312.

Note that all efficiency specs in the data sheet are for boost or for an
unusual 1:1 Vin:Vout mode.
No buck data given AfAICS. However, buck efficiency is usually slightly >
boost efficiency so over 0% should be possible in all cases.

Note - I think that IC should provide  a fine solution. And, properly done,
a better one than the 5 cell linear one.
But 5 cell linear is quite a hard act to beat overall and many switchers
would not manage on many counts.



R
--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.