Thermal Design Power (TDP) is the amount of thermal power an integrated circuit generates under T_CASE,MAX. A TDP of an IC represents that upper point of the thermal profile and is used for determining the appropriate thermal solution design target. TDP is a measure of heat and should not be confused with power dissipation which is a measure of the rate of work.

Overview

As an integrated circuit operates, some of the power applied is dissipated in the form of heat. This heat must consequently be removed from the die and out of the system in order to maintain operational temperature range. The ability to remove heat depends on the power dissipation, ambient temperature, and the thermal resistance of the materials used in the construction of the package.

Where the total thermal resistance (ψ_{Junction-Ambient}, ψ_JA) is the thermal resistance of the Junction to Sink (ψ_JS which also includes ψ_TIM) and the thermal resistance of the Sink to Ambient (ψ_SA). Note that this is measured in °C/W. ψ_SA is a function of the heatsink material, its thermal conductivity, and its geometry.

Therefore the maximum allowable resistance can be calculated as