• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 2 answers
  • Subscribers 64 subscribers
  • Views 297 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

CSD19533 - Thermal pad design

CSD19535KTT: CSD19535KTT thermal calculation

Eddie Chou
Expert 6180 points
Part Number: CSD19535KTT
Other Parts Discussed in Thread: CSD19536KTT

Tool/software:

Hi Team, 

Customer reference to our application note "Semiconductor and IC Package Thermal Metrics"

https://www.ti.com/lit/an/spra953d/spra953d.pdf

in this application we suggest customer use Ψjt  to calculate device junction temperature, but customer checked CSD19535KTT datasheet is still use Rθjc to calculate. 

customer would like to confirm can they still use Rθjc to calculate? what is different compare use Ψjt?

Thanks & Regards

Eddie

  • 0
    TI__Expert 7905 points

    Eddie,

    Thanks for checking.

    Ψjt is defined as the silicon junction to the top of the package, we do not specify this in the CSD19536KTT datasheet. The Rθjc in the MOSFET datasheet is different, it is the thermal resistance from the MOSFET junction to the drain tab/exposed thermal pad.

    We have done some measurements and although no guarantee, if the customer is looking to heatsink the top of this D2Pak package, then they could use a thermal resistance of ~30degC/W for the silicon junction to the top of the plastic.

    Thanks

    Chris

  • 0 in reply to Chris Bull
    TI__Expert 6180 points

    Hi Chris, 

    Thanks for explanation, however customer confused the Rθjc in datasheet is 0.5°C/W in datasheet, it is much different than Ψjt  we suggest above. 

    If customer use heatsink, they should use 30degC/W  to calculate the Junction temperature? 

    Thanks & Regards

    Eddie

  • 0 in reply to Eddie Chou
    TI__Mastermind 38130 points

    Hi Eddie,

    The primary path to remove heat from this D2PAK package is thru the drain tab and into the PCB. Heat sinking on top of the package may not be very effective because the thermal resistance thru the top of the plastic package it is relatively high. Yes, the customer should use 30°C/W for Rθjc(top). Please see technical article at the link below for more information on thermal resistance of TI's FET packages.

    https://www.ti.com/lit/ta/ssztb80/ssztb80.pdf

    Best Regards,

    John Wallace

    TI FET Applications