I have a unique situation where I will lose Vin to my device/voltage regulator for about 10 seconds.
I tried the following circuit thinking it would solve the issue by using a 9V battery and enabling the MOSFET for those 10 seconds or so. VIN is tied into my VIN to my voltage regulator circuit. 12V through another Schottky diode is applied to VIN as well. However, this 12V can drop for about 10 seconds which kills all power to my switching voltage regulator. I am controlling the MOSFET with IO7 from an esp32. I only want to use the 9v battery as an uninterrupted battery backup for those 10 seconds.
The problem I run into is that anytime the battery is connected the board powers up. The voltage regulator I am using is TPS54202DDCR. D1 is SS2210. I do not understand how this is possible.