Power consumption for reverse polarity protection using p-channel MOSFET

Question

I'm looking for a way to implement reverse polarity protection for a circuit that runs from a CR2032 battery (The operating voltage of the circuit is from 1.8 V to 3.2 V).

I'm considering using the Si4421DY MOSFET as this seems to have low Drain-source on-state resistance. Furthermore, the gate opens at a low voltage of 1.5 V.

However, I'm not able to figure out how much power this circuit consumes when the drain-source is kept open (except for power dissipation caused by the current and the internal resistance? Is there a current going through the gate when voltage is applied to the gate?

Also, do I need to add some kind of ESD protection for the gate pin?

Answer 1

Every MOSFET gate consumes virtually zero current.

Technically this is incorrect; the value is typically on the order of nano-Amps (0.000000xxx Amperes.) Because it is so little, it is often disregarded.

You can think of the gate as being one leg of a capacitor. Apply a voltage there (to charge the gate) and that voltage wants to stay there almost indefinitely.

In a computer CPU, there are billions of gates, and the vast majority of power the CPU uses is in toggling those gates. When the PC is working hard, power consumption is many times higher than when it is sitting idle, because many less gates are toggling.