I think i'm just going to directly connect the solar panel to the battery with a schottkey diode. Solar panels simply don't generate enough current to damage the battery unless I go to the sahara or something. I wonder if there are constant voltage solar panels.
By the way, thanks a lot for helping clear up the misconceptions - I should've guessed that that tiny chip wouldn't be able to supply 1 amp.
EDIT: How about a small voltage booster chip? Wonder what those efficiencies are, and if it's worth it.
EDIT NO.2: Okay, so the battery charging circuit's done, time for the battery supply voltage itself. I'm planning to charge this thing via USB. Now USB gives a nominal 5 volts, ranging from 4.75 to 5.25 according to their specs. 5v NiCD battery (4 AAs in series?). So just use a MAX756 chip to boost the voltage high enough to charge the batteries, then another one to drop the voltage when charging ipod.
Is it just me, or am I making this too complicated?
Brainstorm session Fin.
NOTE:
So, due to the difficulty in sourcing a 5v NiMH battery, this is my plan.
When charging:
Solar cell tied directly to battery.
USB input tied to MAX756 chip, giving output voltage high enough to charge four NiMH batteries in series. Use above IC to control battery charge.
When discharging:
Battery connected to
this IC, providing a high efficient stepdown to 5 volts. Batter positive terminal connected to SHDN of step-down IC by a few diodes and a resistor, providing shutdown when battery voltage too low.
... Is there an easier way?