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Which package of the TNY287 has lower RTH(JA) in our layout?

Flyback

Well-Known Member
Thread starter #1
Hello,

We have designed a 5W, 24V Offline Flyback SMPS (240VAC input).
We are using a TNY287 controller which also comprises the switching FET.
There are three different package types of the TNY287.. the SOIC8, PDIP and ESOP.

We do not have room for a heatsink. As such, we are wondering which package will have the best thermal withstand, the PDIP, or the ESOP?

We realise that the ESOP has the lower Rth(JA) figure. However, that Rth(JA) figure (from pg 12 of the datasheet) concerns a single sided PCB. Though we have a double sided PCB, and so we suspect that the PDIP will actually end up having the lower RTH(JA) value, since the PDIP has metal legs which go right through the PCB, and get soldered to thermal copper pours on top and bottom layers.
So do you agree, that in our case, the PDIP will have the lower RTH(JA) value?

Please find attached the view of the layout with PDIP, and then with ESOP (red is top copper, blue is bottom copper)


TNY287 datasheet:-
https://ac-dc.power.com/sites/default/files/product-docs/tinyswitch-4_family_datasheet.pdf
 

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gophert

Well-Known Member
Most Helpful Member
#2
There are plenty of competing heat transfer issues as you started to describe - there are many more that you left out.

The clearest piece of information on the datasheet is on the last page. Select your region and preferred mode of communication. Go.
 

Flyback

Well-Known Member
Thread starter #3
Thanks, i have put the question on the power.com forum, which is scouted by their apps guys...but answers dont always come.
 

kubeek

Well-Known Member
#4
The die of the esop package is directly connected to the power pad, the other packages likely have only bondwires between the die and the pins and will have a lot worse thermal resistance, as witnessed by the datasheet.
 

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