Power MOSFET

Hello,

Can someone explain about the Absolute Maximum Ratings of Power MOSFET ?
In order to avoid the heat damaging, what shall I pay attention ?
Thank you.

Simple; don't exceed them. Also, many of them will require a heatsink on the mosfet to get anywhere close (unless the data shows maximum ratings explicitly with no heatsink).

Absolute Maximum ratings are values you should never exceed. Exceeding the
values risks device destruction.

I would keep the operating junction temperature at less than 80% of the
absolute maximum junction temperature. I have a FAQ at
http://wiblocks.luciani.org/FAQ/faq-rtheta.html

(* jcl *)


www: http://www.wiblocks.com
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blog: http://luciani.org

well there are MOSFETS for 100 A and up! But you alwys have to consult the datasheet, and the diagrams in the appendix..

The marketing line "..so and so many amperes..." is only half of the truth!!

In order to avoid the heat damaging, what shall I pay attention ?

Simple, just pay attention to how hot the mosfet/heat sink is getting. If you can't touch it then you should consider how to improve the situation, bigger heat sink or lower the voltage, etc. Ron is a key spec to how much heat dissipation the mosfet will have in a on/off switching application. Also how well (quickly) your driver circuit can charge and discharge the gate capacitance is also an issue in determining power loss (heat) during switching transitions.

Lefty

Is it OK to understand like this:

for example,

  • Drain[ch8722]source voltage VDSS 60 V

Voltage from Power Supply to Drain, maximum 60 V

  • Drain current DC ID 25 A

Ampere from Power Supply to Drain, maximum 25 A

  • Gate[ch8722]source voltage VGSS ±20 V

Voltage from Arduino to Gate, maximum 20 V

?

In order to avoid the heat damage and to keep Power MOSFET for longer time, should I have :

  • Drain[ch8722]source voltage VDSS maximum 30 V

  • Drain current DC ID maximum 12.5 A

  • Gate[ch8722]source voltage VGSS ±10 V (but, the voltage from Arduino (PWM) is 5V, anyway)

Sorry, if I still misunderstanding, but thank you for your advice !

Is it OK to understand like this:

No.

You are not including the power dissipated in the FET (and the junction temperature)
in any of your calculations. The Rds(on) increases with temperature which you
also need to consider. If you are switching the FET at a high frequency you
will also need to consider the switching losses.

(* jcl *)

In order to avoid the heat damaging, what shall I pay attention ?

Pay attention to this web page:-
http://www.thebox.myzen.co.uk/Tutorial/Power.html

with some worked examples at:-

http://www.thebox.myzen.co.uk/Tutorial/Power_Examples.html