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MOSFET (Si/SiC) Forum Discussions

barak_shapira
Level 1
Level 1
First question asked Welcome!

HI

 

I am working with the NMOS IRFR7740 FET

1. Please advice Constant current from this FET

2. On Figure 15 of the DATASHEET there is an explanation on the AVALANCHE current
     Which is limited to 3A 
     Can you please explain about this phenomena.

 

Thanks BARAK

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1 Solution
Neo_Qin
Moderator
Moderator
Moderator
100 sign-ins 10 likes received 50 replies posted

Hi @barak_shapira ,

1. The maximum constant current value depends on the derating calculation:

Tj_max * derating coefficient = Ta_max + Rja_max *Pd_max = Ta_max + Rja_max * sqr(Idmax)* Rdson_max

In this formula, the parameters of Tj_max/Rja_max/Rdson_max  can be obtained directly from the datasheet. Note that Rja is greatly affected by your actual heat dissipation design.

Ta_max depends on your product specifications.

The derating coefficient depend on design experience or your enterprise standards, in most cases, 0.8 is sufficient.

According to the above formula, you can quickly get the most conservative Idmax value. Of course, you can also optimize the above parameters according to the actual application scenario, and a larger Idmax value should be obtained.

On the other hand, by reasonably estimating the Tc, you can quickly get the Idmax in Figure 2.

Neo_Qin_0-1672885511954.png

2.  Power MOSFET Avalanche Design is a complex process that is obviously not suitable for detailed discussion here, we recommend that you refer to Infineon Application Note AN-1005 .

Regards,

Neo

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1 Reply
Neo_Qin
Moderator
Moderator
Moderator
100 sign-ins 10 likes received 50 replies posted

Hi @barak_shapira ,

1. The maximum constant current value depends on the derating calculation:

Tj_max * derating coefficient = Ta_max + Rja_max *Pd_max = Ta_max + Rja_max * sqr(Idmax)* Rdson_max

In this formula, the parameters of Tj_max/Rja_max/Rdson_max  can be obtained directly from the datasheet. Note that Rja is greatly affected by your actual heat dissipation design.

Ta_max depends on your product specifications.

The derating coefficient depend on design experience or your enterprise standards, in most cases, 0.8 is sufficient.

According to the above formula, you can quickly get the most conservative Idmax value. Of course, you can also optimize the above parameters according to the actual application scenario, and a larger Idmax value should be obtained.

On the other hand, by reasonably estimating the Tc, you can quickly get the Idmax in Figure 2.

Neo_Qin_0-1672885511954.png

2.  Power MOSFET Avalanche Design is a complex process that is obviously not suitable for detailed discussion here, we recommend that you refer to Infineon Application Note AN-1005 .

Regards,

Neo

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