Help with USB power switching

[HodgePodge]

Hello all!

I am building a small portable music rig to carry around, to run off battery power when I'm on the go, and be able to plug in into a USB socket at home.

Its basically an iPOD, an amp and a DAC and all of them use 5V so that's not a problem.

For aesthetic reasons I am powering them using 4xAA batteries, and I've noticed that rechargables would give me 4.8V and alkalines give me almost 6.0V which I need to regulate to ~5V. Furthermore, if I add the ability to use USB power, I would need some diodes to keep the USB power from trying to charge the batteries. So with schottky diodes, I would additionally have to factor in forward voltage drops...

Any help would be greatly appreciated.

Thanks!

[mariush]

See an IC like this one : http://www.digikey.com/product-detail/en/TPS2115APWR/296-16940-1-ND/652794

Page 16, Figure 14 shows an example circuit exactly for the design you want.

You can use a fixed 5v switching regulator to get 5v out of those batteries, see for example MIC4575 :  http://www.digikey.com/product-detail/en/MIC4575-5.0WU/576-1216-ND/771685
Or LT1376.. it's not cheap but it's in DIP package : http://www.digikey.com/product-detail/en/LT1376CN8-5%23PBF/LT1376CN8-5%23PBF-ND/891357


Have a look at others in the same category (source selector / switch): http://www.digikey.com/product-search/en?FV=fff40027%2Cfff80320&mnonly=0&newproducts=0&ColumnSort=1000011&page=1&stock=1&pbfree=0&rohs=0&quantity=10&ptm=0&fid=0&pageSize=25