After going through several datasheets for devices from "Analog Devices’ family of high voltage surge stoppers, overvoltage protection, overcurrent protection, and circuit breaker ICs", I found that external reverse polarity protection is done by the same method but found some differences in some details.
Below are three schematics from three different datasheets. I am interested in finding out why are these schematics different as I think that they shouldn't:
An explanation on how the reverse polarity protection circuit works is present in LTC4366 datasheet (page 20). I should note that the three controllers have similar absolute maximum rating for the gate pin negative voltage of -0.3V.
When comparing the 3 circuits:
The first circuit seems ideal as the diode D1 blocks excessive positive voltage from the input supply passing to the GATE and D2 prevents damage to the LTC4366’s GATE pin by clamping it at ground when the M2’s gate is negative. The 270k resistor R4 is small which will lead to faster switching-on time of M2.
The second circuit rely on the large resistance R5 to block excessive currents from passing to the GATE pin in the event of excessive positive voltage at the input supply or negative voltages present at M2's GATE.
The third circuit uses a diode to block the excessive positive voltage at the input supply but uses nothing to protect the GATE pin from negative voltages (perhaps rely on the resistance of R4(240k).
My question is: If the three circuits are intended for the same purpose of reverse polarity protection, why am I seeing 3 different versions and most important which circuit is the best?