I'm pretty new at hardware side of things and trying to teach myself circuit and PCB design just as a hobby, so. bear with me if I'm annoyingly noob for you.
As a relatively simple first task, I decided to design a USB powered Li-Po charging - 3V3 LDO circuit. It looks like a pretty common hot-plug type design. basically when the USB cable is connected it cuts the Li-Po from the load and charges the LI-PO while powering the circuit from USB power. When USB isn't connected it uses LI-PO power. Here's how it looks:
The problem(?) is with the Schottky diode (D5) which is supposed to block the current from Li-Po to USB (and the MOSFET gate) when the USB cable isn't connected.
I used the following diode for my prototype: https://datasheet.lcsc.com/lcsc/2303141100_MDD-Microdiode-Electronics--SS54_C22452.pdf
Anyway, after getting 5 prototype boards I noticed: When I unplug my USB and plug in a LI-PO Battery (when the Li-Po is at around 4 V) I see 2.55 V at the Schottky's anode terminal. Now I know you're supposed to have reverse leakage with a Schottky diode and it can be high. The unit functions correctly, but that 2.55 V is giving me an itch. Is this normal for this diode? At first I thought the diode may be faulty but all 5 prototypes consistently have the same voltage at that terminal with that 4 V Li-Po.
If this is normal, is this a problem in general? (let's say I will power a MCU board with this)
I'm not sure if it's relevant, but the input impedance of the multi-meter I use is 1 MΩ.