While the junction-to-case thermalresistance is higher than an equivalent,non-isolated device, what really matteris the total thermal resistance fromunction-to-heatsink (RthJH). Comparing adevice in ISOPLUS247™ to itscompanion in the non-isolated packagewith an external isolation foil, one can seethat the overall Rth is now lower for thepart in the already isolated package (seeexample).