[solved] Can I power the Electron with an external 3.3V source?

If I have a board with a 3.3v power regulator on it and want to connect the Electron to it, is it save to connect the 3.3V input of the Electron to my supply And also have the USB connected for serial debug? I don’t want to cause a problem with the USB power feeding the 3.3v also.

Hi @jamesarm97 great question.

The 3.3V regulator on the Electron only powers the on-board STM32F205 and supporting logic. The PMIC and 3V8 rail powers the Electron’s Cellular modem. The PMIC 3V8 output takes input from VIN, USB and the Battery (Li+). We need to pull together some more information on how to run the Electron without a battery, so for now I would say running with battery, powered from VIN or USB is the way to go.

It is not recommended to feed the Electron’s 3V3 node with an external 3.3V source. Only use this 3V3 pin as an output for supporting circuitry.

Ok. That helps knowing it needs the 3.8 (therefore 5v or battery). I will just have to hack up the design to have a 5v regulator from the 24v instead of 3.3v and feed that into the VIN pin. How much can the onboard 3.3v source current wise so I can see if it will support my board or I need another 3.3v on top of the 5v just for my stuff.

I actually had to go look at the electron datasheet myself… it says 800mA for 3V3 :wink: Keep in mind this output does not shut off when the Electron’s STM32F2 sleeps, so anything you have loading it down will continue to do so unless you add some kind of series pass transistor which you could control with one of the electron’s I/O.