θja for LM1086(TO-263 and TO-220)

Theta(ja) is a function of the package AND heatsink that is attached to the package TAB.

For TO-263 package the heatsink is the PCB. This includes the copper area soldered to the TAB, internal copper planes, and any thermal vias placed under the DAP to appropriate internal copper planes.

For TO-220 package the heatshink is whatever material is physically attached the package TAB. This could be a commerical heatsink, or simple copper clad.

For BOTH package types the TAB = Vout, so the TAB must be isolated.

I have submitted requests for thermal simulation of the standard datasheet values for LM1086 in both package types. This may take up to to two weeks, but based on requests in the que as of today I would expect this to possibly be ready by the end of this week.

For the TO-263 package the Theta(ja) will be rated for mounting per the JEDEC Higk-K pcb.

For the TO-220 package I will need the lab to define what criteria is used for determining Theta(ja).

The LM1085 datasheet has some extra information for Theta(ja) for the TO-263 package (LM1085IS). See the table at the bottom of page 11.

Since die size and die attach are similar, and the lead frame is exactly the same, the values shown should be very close to the LM1086S.