switching frequency 5206-2G
i can't find the switching frequency which the FET's can tolerate


From the data sheet: -



The worst case is going from Source OFF to Source ON to Source OFF = 30 us + 5 us = 35 us. Given that you want a decent level of switching efficiency the switching time of 35 us ought to be no more (open to debate) that 5% of the cycle time. That makes the cycle time 700 us or, a switching frequency of 1430 Hz.

It might work at a higher frequency quite effectively (lighter loads) but there's nothing in the data sheet to underpin this. Note that in the table above it says: -

(Device Active for &gt; 1 ms)


And that should inform us that they are recommending a switching frequency of 500 Hz.