TMP75: Temperature Transfer

Dear Kevin - 

Please refer to specification values in Table 6.4 on page 4 of the datasheet: http://www.ti.com/lit/ds/symlink/tmp75.pdf

Here below this table you will see a link: http://www.ti.com/lit/an/spra953c/spra953c.pdf (Semiconductor and IC Package Thermal Metrics) - 

In this document is describes the importance and usage of the parameters we specify in that Table 6.4: RθJA (section 1), RθJC(top) (section 2.4), ΨJT (section 3), Rθ(JB) (section 4), and ΨJB (section 5.1)

For what you specifically asked for, the junction-to-case thermal resistance metric was originally devised to allow estimation of the thermal performance of a package when a heat sink was attached. EIA/JESD51-1 states that RθJC is, “the thermal resistance from the operating portion of a semiconductor device to outside surface of the package (case) closest to the chip mounting area when that same surface is properly heat sunk so as to minimize temperature variation across that surface.” Though no current JEDEC specification is available defining RθJC, a fairly universal industry practice exists for measuring RθJC. 

You can see this method in section 2.1 of the same application report: http://www.ti.com/lit/an/spra953c/spra953c.pdf