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[moved] Mosfet RDS on, determine suitable replacement mosfet for dcdc boost converter

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Chevytrucknick

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I have a 400 watt boost DC-DC converter that.
Input voltage: DC 6V~40V
Input current: 15A (max)
Output voltage: DC 8V~80V
Output current: 0 ~ 9.99A.
I want to replace the mosfet with a little higher ID ratting, just to help with heat. The current mosfet is an knock off of SPP80N10L. The issue I'm having is I don't know enough abouts RDS on to make a selection. The current RDS on is 14 M ohms, does this need to be exactly the same for the replacement. What effects might there be if I increase or decrease RDS on resitance.

Thanks for your time
 

10A^2*0.014=14W dissipated in the FET for the on-time.
Multiply by FET's "on" duty cycle for rough conduction
loss power. This is where Ron affects heat. Power rating
involves Ron on the input side, package, heatsink thermal
attributes and supplied airflow on the exit side. It matters
little if you have a 1oC/W or a 2oC/W thetaJC package if
you put in onto a inadequate heat sink or feed it still air.

Less Ron is better until it costs you something, like more
switching losses than you shed conduction loss by the move.
Typically you gain (lower) Ron by die area or lower BVdss,
your two handles on the drift region resistance.
 

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