Thermal Resistance calculation
1) Thermal Resistance
The heat caused by the power loss Ptot in the active semiconductor region during operation results in an increased temperature of the component. The heat is dissipated from its source (junction J or channel Ch) via the chip, the case and the substrate (pc board) to the heat sink (ambient A). The junction temperature Tj at an ambient temperature Ta is determined by the thermal resistance Rthja and the power dissipation Ptot:
