# Split rail DC/DC converter

The input voltage of my system is ±15V. I need to generate the ±5V voltage. As I need it to power precise analog components (ADC, op amps), my plan is to use DC/DC converter for reducing it to, lets say ±7V, and than to use linear regulator (like LT3032) to get the required ±5V (as linear regulators in general have lower noise). As total current of my system is about 1A, I would avoid solution with only linear regulators because of substantial dissipation. However, I am not sure how to implement DC/DC conversion for negative rail. I know that there are options for supply inversion (make negative rail from positive), but it seems (maybe I am wrong) that those inversion rails circuits are usually for currents less than 1A. And those circuits only use positive rail, although I have also the negative one coming to the system. I saw somewhere schematic with two (non-isolated) DC/DC converters, connected like in the following figure, but I am not sure if this is possible (at least work for higher currents)? Please suggest what would be the proper solution.

• You should use isolated dc/dc converters for this. – Hearth Oct 7 at 13:22

Yes but redrawn looks like this.

simulate this circuit – Schematic created using CircuitLab

If done with 1 IC on a custom PCB it would look like 2 independent circuits with Nch for postive switches and Pch for negative.

Some are independent adjustable, others tracking single control adjustable and others fixed Buck regulators.

You can create a split rail +/-V out also with other IC's that can share 1 inductor but multiple switches inside IC.

PSU AC-DC modules are pretty Cheap to buy these days online < $0.5 to$0.1/Watt and you can get +/-5V free off your old PC MOBO or PSU

Usually an opamp or ADC doesn't need 1A current for negative rail, therefore a charge pump is used. In your application, also two LDOs from +/-15V would suffice.

However if you need dual supply, I would recommend you to use already made DC DC module for that. They come from various manufacturers: Murata, Traco Power, TDK Lambda, Recom, ...many others. You can choose from non-isolated or isolated types. It will save you lot of work and testing.