Hello Guys,



Question 1 :
This mosfet will turn ON with minimum gate voltage of 1.2V.
Is it correct ?

Question 2:
For Vds =3V, Vgs=3V Id=100A (as graph show)
Is this correct assumption while the datasheet say max Id =28A




Question3. Power dissipation then I2Rds(on) = 100*100*5mohm = 50W which is far from datasheet

 

This mosfet will turn ON with minimum gate voltage of 1.2V

Yes, for a definition of on = 250 uA.

 

Generally, the Specs will have a "range" which is usually Temperature dependent.
All the Specs can't be put on one graph,
so you have to check multiple graphs against each other to get the big picture.
At 28-Amps, you are at the Heat Dissipation Limit,
but the Chip and Package are probably capable of a ~200-Amp "Pulse", of VERY SHORT duration.
28-Amps is a continuous rating WITH ADEQUATE HEAT DISSIPATION.

For a quick overview of the "working" Threshold-Voltage, look at the Gate "Charge" curves,
where you see the Curve go "flat" in the middle of the graph, that's the Voltage you are interested in.

 

Wow! My interpretation of the datasheet is that for a Vds of 3 volts, the maximum Vgs you can have to stay within the Id Max of 28A is about 1.75 volts. Alternatively, for a Vgs of 10 volts and an Id of 28 A, the maximum Vgd is about 250mv. However, I am a novice.

 

Question 2:
For Vds =3V, Vgs=3V Id=100A (as graph show)
Is this correct assumption while the datasheet say max Id =28A

That figure cites Note E:


The 28A drain current is continuous at an ambient temperature of 25C:

 

ON does not equal on.
An average transistor will draw ID=0.00025A with a Gate voltage of 0.8V. OK 250uA is not really on!

Next graph shows 2.5V is not really on either. Depending on your definition of on. If you want to use the part at 25A you need a good solid 3.5V on a average part. (worse case?)

 

That figure cites Note E:
View attachment 233180

The 28A drain current is continuous at an ambient temperature of 25C:
View attachment 233181
View attachment 233182
View attachment 233183

ON does not equal on.
An average transistor will draw ID=0.00025A with a Gate voltage of 0.8V. OK 250uA is not really on!
View attachment 233185
Next graph shows 2.5V is not really on either. Depending on your definition of on. If you want to use the part at 25A you need a good solid 3.5V on a average part. (worse case?)
View attachment 233186

Thanks for your reply !
I still do not understand if you say 3.5V for 25A and where did you get this information !
What is current at 3V ?

Datasheet says : 16A at 2.5V


And even i may use two parallel MOSET to half the current.

Regards,

 

The First thing that you should do is to not keep us in the dark any longer ........
What is the End-Result of your project ?
What are you trying to accomplish ?
What Problem are you trying to solve ?

Using 2 MOSFETs will not fix a Heat-Dissipation Problem.

Why are you attempting a project using an SMD Device when you haven't
learned how to interpret a Data-Sheet yet ??????
Do you know how much effort it takes to design a working, stable, SMD Project ?

There are hundreds of "Though-Hole" options that are much easier to learn with.
If you will just give-up some info on what you are building, it might save a huge amount of time.
.
.
.

 

Why do you keep talking about 3V Vds? You do not want anything like 3V across d and s when the MOSFET is on.

The chart shows that the device is nearly fully on at Vgs = 4V, and look at the Vds there. It is well inder 1/10 of a volt at the rated current of 28A.

Bob

 

In the red circle, the 16A is a test condition. It does not say much about using the transistor at 16A. Condition is Vds is 2.5V and current is 16A, the results is ?.?/4.4/5.8m ohms. As Bob said, increasing the Vgs causes the on resistance to drop. 4.4 to 3 to 2.6 as shown in the table. (more or less the part should have 1/2 the heat at Vgs=10 compared to Vgs=2.5V) This is at 16A, if the current is more than 16A the ration of heat savings gets even greater.

Along this same line notice at 125C (hot) the on resistance goes up. The hotter you run the part the higher the resistance and thus the hotter_hotter the part.