I’m in the process of designing a WLED carrier-board for the XIAO ESP32S3 attached to a 5V/14A power supply.
I’d like to power the XIAO via its 5V VIN/VBUS pin directly from the PSU.
The support page suggests to use any kind of diode when powering this way, probably as to not feed current back to the PSU when USB is attached?
My 2 questions:
What Vf (forward voltage) is acceptable? My understanding is that the voltage-drop across the diode reduces the voltage for the ESP? Is <1V a good starting-point?
What’s the suggested current-rating for the diode? I would’ve gone with a 1A Schottky?
I looked at the board’s schematics and the datasheets of the 2 ICs and it appears to me that the module is powered off of 5V directly. No diode used.
Or are you suggesting something else? Would you be so kind to elaborate?
My understanding is that 5V gets fed by the USB connector of the Xiao to the charging IC which charges the BAT and feeds the 3V3 regulator. When the power is sourced from the battery the ETA6003 directs current from the battery to the regulator and into the 3V3 of the Xiao?
But I think my question is answered. Since there is no diode to be found, the Xiao can be powered directly from 5V. Kinda curious as why Seeed does not follow their own suggestions in the Wiki?
somehow it seems to be alot of confusion with regard to powering… as for me i use the expansion boards because i am an experimenter and not a developer the big concern is back feeding power to a computer or sensitive device on the USB
Hi, I’m currently trying to figure out if I need a diode before the 5V pin for my circuit, and I’m a bit confused. Is it true you only need one if you plan on using the external power and usb port at the same time?
Hi edo,
If you plan to connect an external power supply and USB at the same time, it is recommended to connect a diode to both for safety. The power will be supplied from the side with a higher voltage, preventing backflow to the side with a lower voltage.
Connecting the outputs of two power supply circuits without diodes may work, but since I do not know the details of the power supply circuits, I recommend that you prioritize safety.
Hi there,
YES… The diode is only there to protect the device if current try’s to shunt through if you connect both sources Strongest will win and Xiao will hurt the battery charger circuits.
There is a diagram and a pretty complete explanation with current paths for each Scenario on here somewhere. Search the battery threads for Xiao
@msfujino@PJ_Glasso Thanks for the replies. It’s true, safety is important. I will add the diode anyway in case I ever forget to unplug the power. It’s only a small investment.
PJ 