I want to supply my xiao-esp32c3 board mainly with 3,3V at the 3V3 pin and would like to load my programme at the same time at the 5V USB-c Port.
Is there already an internal fuse like a diode so that nothing is destroyed when two voltage sources are connected?
Thank you very much.
The following link shows a circuit diagram of the power supply section.
It is not intended to power XIAO from the 3V3 pin. The 3.3V from LDO will conflict with the 3.3V from the external source. It may not be destructive, but you are on your own if you implement it.
‘Charging characteristics of XIAO_nRF52840 and XIAO_ESP32C3 - #2 by msfujino’
My plan is as follows:
I want to use a lifepo4 cell. Prodection is already done.
The problem is the voltage range from 2,5V to 3,6V.
So i decidet to use a low power stepup-stepdown converter to get 3,3V: Tps63020
As i found out at the datasheet, the Seeduino ESP32C3 board is using a LDO regulator to convert the 5V from the USB to the 3,3V for the controller: XC6210B332MR
I think there should be two situations considered:
The difference could be a little bit different, but i thing the maximum difference is not higher than 200mV.
The voltage from the XC6210B332MR is a little bit higher than Tps63020, and inversely.
If the voltage from the Tps63020 is a little bit higher than the XC62…, i do not think there is a Problem.
But if the voltage from the XC62… is greater than Tps63020?
“7.3.5 Overvoltage Protection If, for any reason, the output voltage is not fed back properly to the input of the voltage amplifier, control of the output voltage will not work anymore. Therefore, overvoltage protection is implemented to avoid the output voltage exceeding critical values for the device and possibly for the system it is supplying. The implemented overvoltage protection circuit monitors the output voltage internally as well. In case it reaches the overvoltage threshold, the voltage amplifier regulates the output voltage to this value.”
I can not detect a Problem 
I have read the two datasheets and as long as the TPS63020, XC6210, battery and USB 5V are working properly, I don’t see a problem.
The regulator’s protective function can only control its own internal elements, so I don’t know if it can handle multiple failures or any external defects.
I have experienced problems in the past, as shown in the link below. Since then I have not connected the outputs of multiple regulators to avoid unnecessary problems. If you are trying to build a product and not just a hobby, I suggest you give this plenty of thought.
‘XIAO Expansion Board trouble’
‘#New Product# Seeeduino XIAO Expansion Board – explore infinite possibilities of Seeeduino XIAO - #4 by msfujino’
‘Xiao Expansion Board’
