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Electronics => Electronics => Topic started by: Commanderbob on June 10, 2008, 07:47:14 PM

Title: Best way to get 3.3V from 2AA
Post by: Commanderbob on June 10, 2008, 07:47:14 PM

I am making a hand held GPS unit. The system is going to run on 3.3V and be powered off 5V. The GPS unit is very sensitive to it's supply voltage it MUST be between 3.1V and 3.5V. What is the best way to get that kind of voltage from two AA? I have a 5V boost regulator that I could then regulate down to 3.3V but that seems inefficient. I don't know what to do as the AA will start above 3.3V but then drop down over their life. Any ideas?

EDIT:I could also use a Li-Ion 3.7 battery
Thanks,
Justin

Title: Re: Best way to get 3.3V from 2AA
Post by: AndrewM on June 10, 2008, 10:14:58 PM

Your best bet is to regulate 5V down to the 3.3V, either a standard regulator or a switching regulator(if you are very power conscious) will work fine.

Title: Re: Best way to get 3.3V from 2AA
Post by: Commanderbob on June 10, 2008, 10:20:40 PM

Right before you posted that I cam across this (http://www.edn.com/archives/1998/110598/23di.htm) solution. The part on the regulator is about 2/3 down the page. This will help with efficiency and number of components.
EDIT:That chip is obsolete but this (http://focus.ti.com/lit/ds/symlink/tps61201.pdf) looks like a winner. :)
Thanks,
Justin

Title: Re: Best way to get 3.3V from 2AA
Post by: JonHylands on June 11, 2008, 05:34:37 AM

I use one of these for that...

http://www.dimensionengineering.com/lvboost.htm (http://www.dimensionengineering.com/lvboost.htm)

- Jon

Title: Re: Best way to get 3.3V from 2AA
Post by: TrickyNekro on June 11, 2008, 10:51:18 AM

LP3873ET - 3.3 :)

Happy projects

Title: Re: Best way to get 3.3V from 2AA
Post by: alessio136 on June 11, 2008, 12:20:21 PM

Quote from: TrickyNekro on June 11, 2008, 10:51:18 AM

LP3873ET - 3.3 :)

Happy projects

wow, up to 3 Amps!

the proplem is thet I only see SMT packages...

Title: Re: Best way to get 3.3V from 2AA
Post by: airman00 on June 11, 2008, 03:56:58 PM

get one of those boards that convert SM to DIP

Title: Re: Best way to get 3.3V from 2AA
Post by: Commanderbob on June 11, 2008, 05:19:48 PM

I can't use a LDO regulator as the voltage can be lower then 3.3V. The regulator I posted before takes the full range of the Li-Ion battery and outputs 3.3V no matter if it is 4.2V or 2.8V.

Thanks,
Justin