TMS320F28335: Creating a two-resistor model for a PTP package

Hello,

I would take a look at this app note: https://www.ti.com/lit/an/spra953d/spra953d.pdf it goes into more detail on how these thermal coefficients are calculated, and should give some insight on the PsiJT parameter vs ThetaJA.

Best,

Matthew

RJB (7.9 deg/W) and PsiJB (6.1 deg/W [without air]) are similar values, but RJC (10.2 deg/W) and PsiJT (0.11 deg/W [without air]) are an order of magnitude different. Why?

What is the difference between the two red circle values?

If the differences are listed in the spra953d.pdf, please let me know the page numbers.

I would look at page 8/9; it explains the derivation of PsiJt, and its applications.  The delta between PsiJT and RThetaJC is also addressed in this section.

Best,

Matthew

The  https://www.ti.com/lit/an/spra953d/spra953d.pdf has a total of 15 pages.
Should I refer to pages 8/15 and 9/15?
Please also let me know the item numbers, such as 3ΨJT, Junction to Top of Package, etc.