Using a power MOSFET for reverse current/battery protection

Question

In the setup below, I am using an FQP47P06 power MOSFET for reverse current/battery protection.

The picture doesn't show it, but the battery voltage is 36 V and the current passes through a 12 V voltage regulator before reaching the MOSFET.

The relation between drain current and gate-source voltage and drain-source voltage, respectively, is illustrated in the following graphs:

Let's say that I need a maximum current of 10 A for the load. Is it possible to reach this if I apply a gate-source voltage of 12 V? How do I calculate, based on the applied gate-source voltage, how much drain-current I can acquire?

Answer 1

The graphs you posted show that Rds(on) doesn't get much better beyond Vgs = -6V or so. They go up to -10V, so we can assume -12V will be about the same.

Look in the data sheet at Figure 9, "Safe Operating Area". This shows the maximum current vs. Idss based on thermal rise in the device. This assumes -10V Vgs, which is slightly conservative compared to your -12V Vgs. This would be reasonable for your design.

Otherwise, it's based on the Rds(on) at your given Vgs, your target current (Idss) and the allowed thermal rise.