Power Supply Thermal Design Guide
Thermal design is critical for power supply reliability and performance. Excessive temperature reduces efficiency, accelerates aging, and can cause failure. This guide covers thermal design fundamentals for MPS power management ICs. Junction temperature Tj = Ta + Pd × Rth-ja, where Ta is ambient, Pd is power dissipation, and Rth-ja is junction-to-ambient thermal resistance. Keep Tj below maximum rating (typically 125°C or 150°C) with margin. Thermal resistance has three components: junction-to-case (Rth-jc), case-to-heatsink (Rth-ch), and heatsink-to-ambient (Rth-ha). For PCB-mounted ICs without heatsinks, Rth-ja depends on PCB copper area, thickness, and airflow. Increasing copper area reduces thermal resistance. Typical values range from 30°C/W for large copper area to 80°C/W for minimal copper.
💡 FAE Insights
Professional Insight
Thermal issues are a leading cause of field failures. Always calculate worst-case junction temperature and include margin. When in doubt, provide more copper area or add a heatsink. The cost of over-designing thermals is much less than a field failure.
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Customer Feedback
"Following the thermal design guide helped us achieve reliable operation at 85°C ambient with proper copper area and thermal vias."