# I have a 5 volt converter but I also need 3.3 volts, what should I do?

Goal is to get 5V and 3.3 V output by the use of a buck/boost converter. Important is to use a converter instead of an LDO for heat reasons.

I want to draw minimum above 0.8A, preferably 1-1.2A at the 5V and potentially around 0.4-0.6A at the 3.3. My input will be aything above 7.4V and below 18V.

I want to add a buck converter to a circuit to reduce the voltage to 5V and then to 3.3V. I came accross this buck/boost converter (TPS63060DSCR) which provides enough current and has a suitable Vin range for my application. Here is the schematic according to the datasheet which outputs 5V with the implicitly calculated resistors for any given Vin.

and here's the datasheet: tps63060 datasheet

EDIT: i realised I made a mistake in my circuit design. Here is the updated version:

At the place of the cut, I also realised I could just use an LDO that converts the 5V to 3.3V since this is not a big step down so it will probably not overheat if i pick a powerful enough regulator, in addition to the fact that it will probably also not draw so much current.

• Comments are not for extended discussion; this conversation has been moved to chat. Jan 15 at 20:45
• Use two buck converters in parallel then. Diodes Inc makes a suitable type that supplies up to 2A, in an SOT-6 package. Link: diodes.com/assets/Datasheets/AP62200.pdf Jan 15 at 20:48

## 1 Answer

• 18 V is 6 V above the maximum input voltage of your converter IC. So, that won't do.
• I don't understand what you mean with "I don't know where to place the resistor. The datasheet extensively answers that – even on the very first page.
• There's plenty of other DC/DC converter ICs from the same manufacturer. Every single of their datasheets has an example circuit. Even better: TI.com has what they call "WeBench power designer" and it draws the schematics for you and gives you the right components.

implicitly calculated resistors for any given Vin.

The resistors have nothing to do with Vin.

I want to add a buck converter to a circuit to reduce the voltage to 5V and then to 3.3V.

You can do that, but it seems unnecessary, as it puts additional load on the 5V rail, and saves you no components. Also, it's worse for noise, but I doubt that's relevant here.

• 18V is just a guideline, 12 V are also good enough. I forgot to delete this, I was trying to add a voltage divider on the output to get 3.3v out as well but i realized thats a bad idea coz of the load not being constant. I made a new schematic which did feature the resistors on i believe correct places but i should have an LDO there instead Jan 16 at 8:46