MicroPython Forum (Archive)

Referring to this schematic:
https://dl.espressif.com/dl/schematics/ ... v4-sch.pdf
and being aware not to supply an EXT_5V while connected to the USB, imagine my confusion when I supplied +5.0 Volts to the EXT_5V pin and the AMS1117 acts like a short circuit.

It heats up really quick and drags the external 5V 1Amp supply down to ground. What is really convenient is that the AMS1117 is not damaged by this abuse.

I noticed that VBUS is also supplied to the CP2102 and that its internal 3V3 regulator is bypassed, ie CP2101 VDD is connected to REGIND. Because of D3 I believe that the EXT_5V should not get to VBUS.

Is there some other step one needs to do before I can achieve proper EXT_5V operation.

Hi davef,

are you sure you are using an official devkitc_v4 ?
I ask you that because, as I know, you are able to connect external 5V supply on EXT_5V pin while USB is also connected.
The SCHOTTKY DIODE BAT760-7 is there for that.
But I know that with unofficial devkit_c like GOOUUU board (with yellow pin), 5V USB and EXT_5V pin are connected together.

Hi Patrice,

Thanks for the response. The board says ESP32_devkitc_v4 but is likely to be a clone.

I test software via USB and rshell but want to deploy with an external 5V supply and use WebREPL. I am currently using a powered-hub as what happens when I apply EXT_5V is contrary to 40+ years of analogue design experience. I did disconnect the USB before applying EXT_5V.

As far as the BAT760-7 is concerned my understanding is that as long as you keep EXT_5V below 5.3V then there shouldn't be a problem with feeding excessive voltage back-up the USB cable.

Dave