Thinking of using the Seeed XIAO SAMD21 board - is the 5V pin connected directly to the USB-Port ? (or is there a protection diode inbetween) ?
Although there is a diode in the schematic, there is a big possibility that it is not actually implemented. It is easy to find out by measuring the resistance with a multimeter or the like.
The 5V labelled pin at the board side seem directly connected to USB VBus. With a multimeter I can see a 0 Ohm connection, and when running, the voltage is 4.96V. Wit a diode, the voltage would be lower. Other XIAO boards label that pin as VBus.
So the XIAO SAMD21 schematic seems to be wrong with that respect.
thank you robert-hh ! I appreciate your measurement. And good you pointed out the wrong schematic!
The 5V pin is not directly connected to the USB port, but it is connected to the output of a voltage regulator. The regulator is designed to handle input voltages between 4.2V and 6V, and it provides a stable 3.3V output for the board’s digital circuitry.
You surely mean input, and it does not contradict to being connected to VBus. The regulator provides 3.3V for the CPU from a 5V source, which is the USB or the external 5V pin.