Upgraded a mixing board needing 3 voltages to run off 12V
For 2A Positive/Negative Output Step Down Power Module
These little guys handle a good load, and are fairly easy to use. They come with 3 surface mount resistors set for 3.3V output. Depending on how the leads are attached you get either +3.3V or -3.3V.
The docs describe changing R1 / R2 in order to get different voltages, but I recommend instead bridging across the existing 10K resistor R3 to lower its resistance. I needed a couple voltages for my project, so used 2 modules. By bridging a 5.1K resistor over R3 it ends up being 3.38K, which gives pretty close to 5V. That positive converter runs very efficient -- really cool while delivering about 700ma. In another module I needed -12V, which I got by bridging a 1K resistor over R3 to end up with 909Ω. This negative-side converter got much warmer, even though it was only delivering about 500ma. So for giving negative voltages perhaps it's not quite as efficient, but still it never gets hot to the touch. Only warm.
One reason I really recommend to bridge resistors on R3 is if any added-on resistors ever fall off, the supply just reverts to a lower voltage instead of snapping to a higher one. So less chance of damaging things. Also in order to mess with Rfb1 / Rfb2 you'd have to remove the existing resistors. So I find it much easier to just play with R3.
The actual soldering of the resistors was really fiddly, since the surface mount resistors are REALLY small. I ended up leaving them in place, and soldering between pins 5 and 7 on the IC. Pin 5 (VSENSE) is on the corner of the chip, and very easy to get to. And really instead of pin 7 (just GND) then there's a nearby capacitor and resistor hanging on ground that you can solder onto. I've got a fairly big iron, and this was about the easiest for me to mess with.
Perhaps evident, but just so everyone is aware -- the converter doesn't boost, it only lowers voltages. And it does it pretty well.
