TPS53515: Theta Jc (top) vs Theta Jc(Bottom)

Bharath Krishna

Part Number: TPS53515

Hi,

We are using TPS53515 and other TI Buck regulators in our PCB.We are performing thermal simulations of our board.The datasheets mention Theta Jc (top) and Theta Jc(Bottom).We wanted to know which value of theta Jc is to be considered for our simulation purpose.(Our Simulation tool has only one theta Jc tab)

Thanks,

Bharath

over 5 years ago

0 Gerold Dhanabalan - Online Design Tools over 5 years ago

TI__Genius 14455 points

Hi Bharath,

Whats the simulation tool that you are using? The device has an exposed thermal pad and thats why the the ThetaJC (bottom) is lower than the Theta JC (top). I am checking with experts on this topic. In the mean time, I would recommend using Theta JC (bottom) as the heat would flow through the thermal pad - as the path of least thermal resistance.

Regards,

Gerold

0 JohnTucker over 5 years ago in reply to Gerold Dhanabalan - Online Design Tools

TI__Guru**** 191445 points

Bharath,

For devices with a thermal pad almost all of the heat transfer will be to the bottom thru the pad. If you use Theta J-C, don’t forget to include the thermal resistance of the solder. You may want to consider using Theta J-B. There is a good reference, SPRA953 that explains thermal parameters.

http://www.ti.com/lit/an/spra953c/spra953c.pdf

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TPS53515: Theta Jc (top) vs Theta Jc(Bottom)