Note that the power dissipation and thermal resistance values in the datasheet are the values under the specified board conditions. It is therefore necessary to evaluate LDO regulators carefully to ensure that they work properly under actual usage conditions.
The following application notes also provide a description of the power dissipation and junction temperature of an LDO regulator.
Application note: Basics of Low-Dropout (LDO) Regulator ICs
Application note: Thermal Design to Maximize the Performance of LDO Regulators