TLV733P-Q1: Thermal information

HI Hayashi-san,

For question number 1: The image did not get posted but this is our standard thermal table:

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For question #2: RθJB is the Junction to Board thermal resistance. RθJC (bot) is the Junction-to-case (power pad) thermal resistance

For Question #3: The ΨJT if the DRV is smaller as the amount of mold compound between the die and the top is much less than the DBV package. 

I hope this answers your questions.

HI Hayashi-san,

I think you are asking for a detailed description of these parameters. If so, here you go:

θJA -  This is the Junction-to-ambient thermal resistance

θJC(bot) - This is the junction-to-case (power pad) thermal resistance

θJC(top) - The junction-to-case (top of the case) thermal resistance

         Note: if you are going to measure this temp using an IR thermal camera you must use the right

                 settings for the emissivity of the surface and very small spot size to get an accurate measurement.

θJB - The junction-to-board thermal resistance. Note: this is from the junction to the pins

ψJT - The junction-to-top-of-package characterization parameter

ψJB - The junction-to-board characterization parameter

Practically, useful terms are θJA and ψJT.  θJA is used to predict the thermal rise above PCB ambient. While once you have the board, ψJT can be used to confirm the actual junction temperature in the application. 

TJ=TA+(θJA*PD) where TJ is the predicted Junction Temperature, TA is the PCB ambient temperature, and PD is the power dissipated (VIN-VOUT)*ILOAD. 

and for ψJT:

TJ=PD*ψJT+ TMEASURED where TMEASURED is the temperature measurement at the top of the package. 

To answer your question on ψJT and the DRV yes, there is physically less material between the die and the top of the case. Looking at the above equation for ψJT the less material or thermal resistance between the die and the top of the package, the closer your measure is to the actual die temperature. 

Does this help to clarify your questions?

HI Hayashi-san.

This is the best image I have for showing the different thermal resistances and why TJA is the best for prediction:

Does this help to clarify?

Hi Hayashi-san,

These are simply characterization parameters. ΨJT is used to calculate the die temperature based on the temperature you measure at the top of the package. ΨJB does the same for the bottom of the package, but this is not practical as you would need to make a special board that allows you to connect a thermal probe to the bottom of the package.

I hope this helps.