Enter your Power Dissipated, Ambient Temperature, and thermal resistance chain — Rth-jc, Rth-ch, and Rth-ha — to calculate your Junction Temperature, Total Thermal Resistance, Temperature Rise, and Max Safe Power before hitting the 150°C limit.
Junction Temperature (Tj)
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Temperature Rise (ΔT)
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Total Thermal Resistance
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Maximum Power at 150°C
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Junction temperature is the operating temperature of the semiconductor die inside an electronic component. It's critical because exceeding the maximum junction temperature can cause device failure, reduced lifespan, or performance degradation.
Thermal resistance values are typically found in the component's datasheet. Look for Rth-jc (junction to case), or check with the manufacturer's thermal characterization data.
If the junction temperature exceeds the component's maximum rating, you need to reduce power dissipation, improve cooling (better heat sink), or use thermal interface materials to lower thermal resistance.
Yes, if you're using thermal pads, thermal paste, or other interface materials between the component and heat sink. These materials add thermal resistance that affects junction temperature.
For general applications, use 25°C. For automotive applications, consider 85°C. For industrial applications, 70°C is common. Always use the maximum expected ambient temperature for your specific application.
You can reduce junction temperature by: using a better heat sink (lower Rth-ha), improving thermal interface materials, increasing airflow, reducing power dissipation, or using components with lower junction-to-case thermal resistance.
Case temperature is measured on the external package surface, while junction temperature is the actual temperature of the semiconductor die inside. Junction temperature is always higher due to internal thermal resistance.