Thermal effect calculator
This calculator and equation help determine the junction temperature of the heat sink. Most commonly used with power devices, calculating the junction temperature of a device works around four criteria: the ambient temperature, the device’s thermal resistance, the thermal resistance of the heat sink and the power applied to the device.
Inputs
Material
Weight
Temperature Rise
Degrees Celsius or Kelvin
Energy
Joules
Output
TJ = Junction temperature
Ta = Ambient temperature
P = Power dissipated
Rcase = Thermal resistance of device junction to case
R1 = Thermal resistance of heat sink
R2 = Thermal resistance of device junction to air
Equations
$$TJ = P(Rcase + R1 + R2) + Ta$$
Further Reading
- Technical Article — Temperature Limits for Power Modules, Part 1: Maximum Junction Temperature
- Technical Article — Small Heat Loads: Big Challenge to Enhance Heat Sink Performance
- Technical Article — How to Keep a Power Transistor Cool Using Heat Sink