- Tj
- Temperature of the junction. Maximum allowed is 175 °C
- Rθj-c
- Termal resistance — junction to case.
- P
- Power to be dissipated.
- Rθc-h
- Thermal resistance — case to heatsink.
- Ta
- Ambient temperature.
- Rθh-a
- The resulting thermal resistance of the heatsink to air.