Whta is the case to ambient thermal resistance for the HKJ package?
Tja depends highly on the final form factor (deadbug vs livebug, board stand off etc.) so, unfortunately, there is no definitive Tja for HKJ package as it is sold as unformed.
But as an approximation, if formed dead bug (lid down) with .015” body to board clearance Tja per JESD51-7 is about 145 C/W.
What would be a typicila for a standard mounting (lead up, no space between the part and the PCB) ? (TPS76901-HT)
Thanks,