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Base on thermal resistance Theta ja= Theta jc+ Theta ca
So basically Theta Ja should be big than Theta Jc.
But we had find some of datasheet show Theta Jc big then Theta Ja.
Could you explain why these Theta Ja is small then Theta Jc?
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Hi,
Apologies for the delay in response.
The Jc value mentioned in the datasheet can be the theta Jc top. In some cases on QFN, it can be more than Ja.
For QFN-68 & QFN-88, please refer to the table below:
|
FBGA |
LT88 |
LT68 |
Ja |
35 |
15 |
16.2 |
Jc |
12 |
5.92 |
3.96 |
Regards,
Mallika
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Hi,
Apologies for the delay in response.
The Jc value mentioned in the datasheet can be the theta Jc top. In some cases on QFN, it can be more than Ja.
For QFN-68 & QFN-88, please refer to the table below:
|
FBGA |
LT88 |
LT68 |
Ja |
35 |
15 |
16.2 |
Jc |
12 |
5.92 |
3.96 |
Regards,
Mallika
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Hi Mallika,
Could you explain more "In some cases" Jc > Ja?
And why your table different with HX3 datasheet?
|
FBGA |
LT88 |
LT68 |
Ja |
35 |
15(15.7) |
16.2 |
Jc |
12 |
5.92(18.9) |
3.96(23.8) |
Is means datasheet information incorrect?
Thanks,
Mitchell
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Hi Mitchell,
The theta jc value in the datasheet which is greater than the theta ja value is the theta jc (top) which is typical for QFN since the heat dissipation at top case of package is higher than the heat dissipation at the bottom where there is an exposed paddle that helps with the heat flow.
Regards,
Mallika