Attached circuit is using in Automotive to protect reverse polarity using P-CH Enhancement type MOSFET.
MOSFET: SSM3J351R,LXHF
Zener: BZX84-B18,235
Resistor: 10K
During normal input voltage (9V to 30V) Zener diode is using to protect gate-source of the MOSFET. MOSFET VGS max is -20V/+10V as per datasheet.
Zener diode should clamp at after 18V of input voltage.
But in this case Zener diode is not reverse biasing
kindly explain the root cause.
Attached schematic portion.
MOSFET: SSM3J351R,LXHF
Zener: BZX84-B18,235
Resistor: 10K
During normal input voltage (9V to 30V) Zener diode is using to protect gate-source of the MOSFET. MOSFET VGS max is -20V/+10V as per datasheet.
Zener diode should clamp at after 18V of input voltage.
But in this case Zener diode is not reverse biasing
kindly explain the root cause.
Attached schematic portion.