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bennieliu
Level 1
Level 1
Distributor - Intron(GC)
5 questions asked 5 comments on blog First comment on blog

Dear Expert:

We meet some question about MOSFET SOA curve.

1.Could you help check if there is a thermal instability limit line exsisting under tp=10us,or  even shorter time for example:tp= 2uS?

bennieliu_0-1698983511967.png

2.Some SOA curves from Infineon MOSFET datasheet gives maximum power limit line without a thermal instability limit line followed, can we say that the thermal instablility cannot happen in this MOSFET if  tp is even shorter, for example, as below two graphs, tp =1uS and tp=10uS, both graphs without a thermal instability line followed ?

bennieliu_1-1698984144940.png

bennieliu_2-1698984578866.png

 

 

 

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1 Solution
Xiangrui
Moderator
Moderator
Moderator
500 replies posted 250 solutions authored 50 likes received

Hi Bennie,

1. We can't provide more information over than datasheet. But you can check by yourself with following explanation.

2.  A MOSFET (or generally a system) is considered to be thermally unstable in case the power generation (P_generated) rises faster than the power dissipation (P_dissipated) over temperature. Thermal instability can occur only if the temperature coefficient of the drain to source current is positive. The question under what conditions such a positive temperature coefficient can be found is answered by the transfer-funtion graph in the MOSFET datasheet showing IDS over VGS for various temperatures. 

So it is case by case. You cannot say thermal instablility cannot happen absolutely. Please refer to SOA in datasheet of devices. 

Additional information: 

Xiangrui_0-1698993492733.png

Xiangrui_1-1698993506877.png

 

 

 

Regards,

Xiangrui

View solution in original post

0 Likes
1 Reply
Xiangrui
Moderator
Moderator
Moderator
500 replies posted 250 solutions authored 50 likes received

Hi Bennie,

1. We can't provide more information over than datasheet. But you can check by yourself with following explanation.

2.  A MOSFET (or generally a system) is considered to be thermally unstable in case the power generation (P_generated) rises faster than the power dissipation (P_dissipated) over temperature. Thermal instability can occur only if the temperature coefficient of the drain to source current is positive. The question under what conditions such a positive temperature coefficient can be found is answered by the transfer-funtion graph in the MOSFET datasheet showing IDS over VGS for various temperatures. 

So it is case by case. You cannot say thermal instablility cannot happen absolutely. Please refer to SOA in datasheet of devices. 

Additional information: 

Xiangrui_0-1698993492733.png

Xiangrui_1-1698993506877.png

 

 

 

Regards,

Xiangrui

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