Are there guidelines to change U3V70A?

Hello everyone!

I’m new to this forum and here is my adventure :slight_smile:

I have a 12v battery and I would like to provide energy to my laptop using this:

battery (11v - 13.4v) → U3V70A → laptop (19v @ 2.5A)

But sometimes I would like to use the same U3V70A to charge my mobile phone (which requires 5V @ 2A)

Since I have necessity to use only these two voltages (19v or 5v) I would like to know if it is possible to use a switch instead of a potentiometer that comes with U3V70A. So the question is:

If a switch is a good idea, which switch resistor should I use for 19v and which resistor should I use for 5 volts and how to wire then? Did anyone here had experience modifying an existing pololu board?

If modifying the U3V70A is not a good idea, then which product you recomend?

IMHO With a switch is much more easier to go from one to another without need to use the potentiometer + multimeter whenever I change it (setting up the voltage is time consuming)

I dont like the idea of using another U3V70A because I’m trying to develop a setup that is lightweight for me to carry on my bike trips, so, just one will do the job perfect for me. And as you can see in the picture, the aluminium case is perfect there (it took me a while to think how to build this aluminium case specific to this circuit) so why not use it for both cases using the same board? :slight_smile:

Bellow is a picture of how is the current setup with U3V70A

Any advice is welcome, thank you!


Hi, Fabiano.

In theory it should be possible to add components to the U3V70A regulator so you can switch between two different fixed output voltages. In practice, how the extra components are added might affect the regulator’s performance. You mentioned using a 12V battery for your input when powering the laptop. Do you also want to use the 12V battery to power the 5V phone charger? The U3V70A is a step-up only regulator, so if you do want to use the 12V battery for both, you will need a step-up/step-down regulator instead. Unfortunately, we do not have any that are optimized for outputting both 5V and 19V or that can handle anywhere near the 7A current of the U3V70A.