R707 = 10KOhm, R708 = 10KOhm, and Q701 is a P channel mosfet (IRLML6402TRPBF)
I'm driving this with a mircocontroller (3.3V). the EXT_READER_SHDN is configured as open drain output.
When EXT_READER_SHDN is 0 (connected to GND) I have :
Vgs = -10.72V (since the 12V is only 10.73V)--> the mosfet in this case is ON (conducting)and 12v_READER = 10.73V.
When EXT_READER_SHDN is 1 (pin floating) I have :
Vgs is around -2.66V (threshold is 1.2V)--> the mosfet in this case is also ON and 12v_READER = 10.73V.
I have already printed the PCB and need to make a temporary fix until the next version. Any ideas of a simple way to be able to open and close the circuit ?
I thought about reduicing the R707 value to likes 2 or 3 KOhms, but this will apply a hight voltage on the microcontroller pin. but since the pin is on open drain, doesnt this mean that I can go crazy and put 12V and have no issues ?
Thank you guys