Hi there! I'm curious about what kind of output protection the Analog Discovery 2's V+ supply output has against back-driving.
I'm using the NXP FRDM-KL25Z MCU board. The P3V3 rail is normally powered (via USB and D11) from a linear regulator (NCP1117ST33T3G) through a protection diode D12:
I have cut the shorting trace on the bottom of J20 so D12 can work. For my testing, I disconnect the USB connection (P5V_SDA) and instead use the AD2 to power the board P3V3 supply rail at 3.3 V and below. However, to update code and debug I need to use the USB connection, so it would be easier to keep it plugged in. I can imagine a scenario where I have the AD2 generating a lower voltage (e.g. 2.0 V) for the P3V3 rail, and I plug in the USB cable. U1 would try to drive the P3V3 rail at 3.3 V, and I don't want to damage the AD2. I can also imagine a scenario where the shorting trace on J20 hasn't been cut, or a shorting jumper has been placed on the J20 header.
Is the AD2 V+ supply output likely to be damaged if a slightly higher voltage is applied in this way with this circuit?
Thanks,
Alex