Can someone help me with reverse polarity protection on 5-12V input and output using a using a P-Channel MOSFET?
How can I calculate which MOSFET, resistor, zener diode I have to use?
I use a 5V 10A power supply.
Electronic – Reverse polarity protection on 5-12V input and output
mosfetresistorsreverse-polarityzener
Related Solutions
I would go ahead and add a second one of the PSMN0R9's in series with the first. When connecting it up put the two MOSFETs drain to drain and the second ones source to the "LOAD_GND". The gates of the two FETs tie together. This is the simplest way to work around reverse polarity protection with MOSFET body diodes.
According to the safe operating DC operation curve you are right at the limit for 10A at 25C. So I'd say it's not going to work for you. Also at 3.3V the thing will be barely on. Even 4.2 it won't be saturated.
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Best Answer
A common rule of thumb for improved long-term reliability is to overrate electronic components by 100%. Examples: For a 12 V system, use a FET rated for 30 V or more. For a peak load current of 3 A, use a FET rated for 6 A or more of continuous drain current.
Because your operating voltage range is relatively low (in FET terms), select a "logic-level" FET. Check the datasheet, but they almost always are rated for 20 V Vgs, so you don't need a zener to protect the gate unless the reverse voltage might be way below -12 V.
A power MOSFET has an internal zener diode between the gate and source. Pay close attention to the orientation of this diode in your circuit.
If your system can tolerate having the MOSFET switch in the GND rather than in the supply, an n-channel MOSFET will cost less and perform better. Plus, the circuit is more simple.