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By madcat207
#11142
I have been thinking of projects to use a new battery with, and one of them that i thought of (using as a spare power supply for a cell phone) requires a 5v input (USB connection) I tried a straight connection, but as i figured, it did not work.

From my understanding, this is a fairly unique part, but if anyone has any ideas, that would be great. :)
By Kuroi Kenjin
#11144
Just look for a Step-up converter. (Or even a Cuk, SEPIC, or Buck-boost). Microchip has a ton of these for just what you're doing. You can sample a few for free if you have a company or university e-mail. Or you can get them on Digikey, Jameco, Mouser, and whereever else pieces-parts are sold. They'll be a small chip, and will require an inductor, a few capacitors, resistors, and a few diodes (one of which being a zener). The datasheet should show you how to hook it all up.
By Kuroi Kenjin
#11154
Yeah, that's what I'm refereing to. I dunno if you're going to find a pre-made board, but you can always work up a small PCB (probably smaller than 1"x1"). Also really nice that the datasheet gives you suggested parts.
By madcat207
#11155
Some of the maxim parts have eval boards, but i cannot find how to order samples.

And while there is enough info out there, i am not sure i have a steady enough hand to solder parts that small (the IC is quite tiny from what i can tell).
By geekything
#11163
I'm actually looking for a part that does the same right now (3.7 LiPoly to 5vdc and 3.7LiPloy to 3.3vdc).

However, I've got relatively high current requirements (~500mA) -- anyone got a favourite part that's *readily* availabe? There are Maxim parts that do this, but they're not available in less than 2500 quantity from Digikey.

-marc
By madcat207
#11187
Maxim's site may be able to get you a few samples. I inquired about a board, so if i hear anything, i will let you know.
By geekything
#11224
http://www.sparkfun.com/commerce/produc ... cts_id=317

I totally forgot that was there. And totally forgot that I have one sitting here!! :roll:

This puppy can take your 3.7vdc and charge it up to 5vdc or higher. Requires a few passives (bypass caps, resistors, and an inductor) -- but that's not unusual.

Best thing for you will be that you can put this all on a solderless breadboard and there're example circuits in the datasheet.

For around $5 you'll be all set.

-marc
By Kuroi Kenjin
#11241
Oh yeah! I forgot, they used that on their ringer circuit. It should more than handle either of your guys circuits (1.5A output).
By Philba
#11245
it's an interesting chip and I'm tempted to use it in a couple of places. one downside is the output ripple seems kind of high. the couple of designs I worked through had more than 100 mV ripple. still, it looks like it might be pretty useful. another slight negative is it requires a pretty large (and pricier) inductor due to its lower switching frequency. Newer smps controllers use much higher frequencies and thus smaller inductors. of course, you pay for that.