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need a suggestion for a 2x AAA to 5V step up circuit

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hako90210

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I'm trying to power a gps in a little box and only have space for 2 x AAA and a few small chips or wires.. I need min 3.3v @ 125ma as this document says .. http://www.billiggps.dk/GM-305.pdf

Does anyone have a suggestion on the best way to power this gps in the pdf with 2 x AAA.. I was looking at the LM2621 but don't know much about electronics , is this a good choice or is there something better.

I'm doing this for myself so looks, price , power life is not important.. If I can find a way to squeeze 30 min of battery life out of 2 AAA.. that would be great.

Or possibly a tiny 5V battery that would fit in the space of 2 AAA.


Thx
 

hako90210

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Not bad but isn't the lm2621 a better choice , this chip seems to need 3.3v
 

Kripton2035

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you didnt read well enought ...
the maxim chip OUTPUTS 3.3 or 5v fixed directly
it works from 1V .. and 0.7v in certain conditions ...
 

hako90210

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well that sounds pretty good , I'll give it a shot , this is my first time trying to build such a thing. I managed to do some board level repair on a few of laptops and then I got a 300-in-1 hobby kit and I'm now I'm in electronics land , hope it works out and they include some schematic ..

Is there possibly software that will draw one for me ?
 

Kripton2035

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on the web link I gave you, there is the schematic at the bottom ...
if you download the pdf file on the same page, you will get the full schematic, with the calculations examples (althought there are almost nothing to calculate for a fixed output !)
regards,
 

    hako90210

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hako90210

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The entire city of Toronto didn't have a max1709 or lm2621. The only
place I could have bought it was through digikey.ca . So I took a suggestion
from the guy at creatron for max756.

Looks like it will do pretty much the same. Total cost $15 with board, caps,socket ic etc..

here goes my first ever circuit schematic ... in photoshop.
 

Kripton2035

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maxim sends free samples if you have a pro email adress (not hotmail, yahoo etc... prefer a xx.com)
just register on their web site and order 2 samples of max1709 ...
 

hako90210

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Well it worked , I'm sure the 1709 is more efficient and powerful but this seems to do the job.
 

hako90210

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And the final circuit ..

Now I need a tiny 2 x AAA charging circuit on the exact same size board.. anybody.
 

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