Positive and Negative 5v from 2 AA Batteries

[robo171]

I'm designing a portable device running off of 2 AA batteries that requires positive both positive and negative 5v power at the same time. What is the best/cheapest way to achieve this?

 

[Chunkysalsa]

2AA batteries would only give you a nominal value of 3V in series. Otherwise it kinda depends on your application of the dual supply. The easiest and cheapest way would be to split a 10V source using voltage dividers. Create a ground at the midpoint and then the reference voltages would be +- 5V. Not super ideal obviously and prone to being unbalanced.

 

[robo171]

I'm working with audio, so balance is important. My best idea thus far has been to use 3 voltage regs: one to step up 3V to 5V, one to step up 5V to a slightly higher level, and one to invert the slightly higher voltage to -5V. Obviously that's not quite ideal either.

 

[MisterX]

You could use one DC-DC voltage converter (regulator) for +5 V, and another one for -5 V (perhaps a http://www.exar.com/Common/Content/ProductDetails.aspx?ID=595" ). Or, you could use one 10 V output DC-DC converter and a virtual ground.

I found http://tangentsoft.net/elec/vgrounds.html" might not be a bad option if you use the 10 V converter option.

 

[robo171]

MisterX: I found the page on virtual grounds very informative, especially for my project! Do you have a suggestion for a step-up that can convert 2-3V to 10V?

 

[MisterX]

You could look on Digikey http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=2556570".

Select all the input voltage ranges with minimum voltages of less than 2.3 V or so. I didn't see any with fixed 10 V output so you may want to look at the adjustable ones with 10 V in the range of output voltages.

You may want to select "Through Hole" under "Mounting Type".

By reading the datasheets you can understand how to use the ICs and what other components you may need to have. There may also may be information on efficiency.

 

[Chunkysalsa]

Tangent's site is great especially if you are working with audio. I actually had a cmoy in mind when I was talking about a resisitive dividing virtual ground.

 

[robo171]

Thank you very much, MisterX. As I dig deeper into Tangentsoft, I keep finding valuable insight for my project. Great find!