I'm designing an embedded system that will be based around a RPi3, combined with the official touch display. In working out how to power the device, I'm getting stuck because the Pi I'm using keeps showing an under-voltage warning when running with the power supply I'm planning on using.
When I connect the official power supply, no under-voltage warnings are shown, using this supply is no option, however, as the device will need to run from a battery. When I power the Pi through a TI LM2596-based power supply (left over from a previous iteration of the project) it shows under-voltage warnings, especially when the display is on full brightness and I'm interacting with it. My multimeter shows a nice 5.0V on the output from the power supply under load, but measuring the 5V gpio pin shows only about 4.65V.
This is what I tried already:
I've eliminated voltage drop in the power cable by cutting the official power supply cable and connecting it to my power supply using a mini-fit jr plug. I also connected a mini-fit jr socket to the official power supply itself, so I can still use that for more testing.
The LM2596 is rated for 3A, so that should not be an issue
The only USB peripherals are a keyboard and a USB ethernet adapter
I tried using a separate power source for the display, but this made no difference
I know the official power supply outputs 5.1V, but from what I understand, the Pi should run fine on 5.0V.
Am I missing something? Should I simply suck it up and use an adjustable power supply set to 5.1V?