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simplify reverse polarity protection w/ high side switch

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wergor:
I have come up with the following circuit implementing a reverse polarity protection and a high-side on/off switch:
[attachimg=2]
M1 and M2 as well as D1 and D2 are of the same type, so I wonder, is it possible to simplify the circuit?

OVP and OCP are not needed (Vin is monitored by a microcontroller and M2 is only switched on if Vin is in a range supported by the load. I_load is also monitored for overcurrent events)

DavidAlfa:
In fact, you need to add few things to make it stable and safe.
There're no gate discharge resistors.
Resistors values are too high, or at least in simulation had very slow switching times, several 10s of ms.
Applying 12V at the gate 12V is ok, but it allows up to 20V, so I suggest using 16V for lowering Rds even more.

I don't see how you could simplify the circuit. If you need reverse polarity protection, you need a second transistor, otherwise the current would pass through the body diode.

langwadt:

--- Quote from: DavidAlfa on October 18, 2021, 02:32:50 pm ---In fact, you need to add few things to make it stable and safe.
There're no gate discharge resistors.
Resistors values are too high, or at least in simulation had very slow switching times, several 10s of ms.
Applying 12V at the gate 12V is ok, but it allows up to 20V, so I suggest using 16V for lowering Rds even more.

I don't see how you could simplify the circuit. If you need reverse polarity protection, you need a second transistor, otherwise the current would pass through the body diode.

--- End quote ---

you can skip R1,R2,D1 and connect the gates

Peabody:
I think the M1 circuit is ok.  But I think M2 needs a gate pullup resistor to the source.  Otherwise there's nothing the bring the gate back high when M3 turns off.

I also think langwadt's suggestion is interesting. If you eliminate R1 and D1 and connect the gates, but add the pullup, then in normal polarity M1 would remain off until M3 turns on both M1 and M2.  In reverse polarity, high input would flow through the body diode of M3, which brings both gates high, and both sources high through D2.  DavidAlpha, could you simulate that?

langwadt:

--- Quote from: Peabody on October 18, 2021, 04:56:46 pm ---I think the M1 circuit is ok.  But I think M2 needs a gate pullup resistor to the source.  Otherwise there's nothing the bring the gate back high when M3 turns off.

I also think langwadt's suggestion is interesting. If you eliminate R1 and D1 and connect the gates, but add the pullup, then in normal polarity M1 would remain off until M3 turns on both M1 and M2.  In reverse polarity, high input would flow through the body diode of M3, which brings both gates high, and both sources high through D2.  DavidAlpha, could you simulate that?

--- End quote ---

M1 and M2 is common source a single resistor is pull down for both gates

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