Voltage Regulator Heat Sink Calculator

A voltage regulator dissipates excess energy as heat — without proper cooling, it can overheat and fail. The Voltage Regulator Heat Sink Calculator tells you exactly how effective your heat sink needs to be to keep the chip running safely. Select your regulator type, enter your input voltage, output voltage, and output current, then set your ambient temperature, maximum junction temperature, and thermal resistance values to get the required heat sink thermal resistance, along with power dissipated, junction temperature rise, and estimated junction temperature.

V
V
A
°C
°C
°C/W

Varies by regulator type - check datasheet

°C/W

Thermal interface resistance

Results

Required Heat Sink Thermal Resistance

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Power Dissipated

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Junction Temperature Rise

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Estimated Junction Temperature

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Frequently Asked Questions

How do I know which thermal resistance values to use for my voltage regulator?

Check your regulator's datasheet for junction-to-case thermal resistance (θJC) values. Common values are 5°C/W for LM317T and 0.65°C/W for LT1084. Case-to-heatsink resistance depends on thermal interface material, typically 0.5°C/W.

What happens if I don't use a heat sink when one is required?

Without adequate heat sinking, the junction temperature will exceed safe limits, causing thermal shutdown, reduced output current, or permanent damage. Most regulators have built-in thermal protection but this causes intermittent operation.

How do I calculate power dissipation for linear voltage regulators?

Power dissipation equals (Input Voltage - Output Voltage) × Output Current. For example, with 12V input, 5V output, and 1A load: (12-5) × 1 = 7 watts of heat must be dissipated.

What's the difference between switching and linear regulator heat calculations?

Linear regulators dissipate power as heat equal to voltage drop times current. Switching regulators are more efficient (85-95%) so heat calculation involves efficiency: Power dissipated = (Output Power / Efficiency) - Output Power.

How do I select an appropriate heat sink based on the calculated thermal resistance?

Choose a heat sink with thermal resistance equal to or less than the calculated value. Consider mounting orientation, airflow, and safety margin. Natural convection heat sinks typically range from 1-50°C/W.

Why is ambient temperature important in heat sink calculations?

Ambient temperature is the baseline from which all temperature rises are calculated. Higher ambient temperatures require better heat sinking to maintain safe junction temperatures. Design for maximum expected ambient temperature.

Can I use this calculator for MOSFETs and other power devices?

Yes, the thermal resistance calculation principles apply to any power semiconductor. You'll need the device's junction-to-case thermal resistance from its datasheet and appropriate case-to-heatsink values.

What safety margin should I include in my heat sink design?

Use a 10-20% safety margin by choosing a heat sink with 10-20% lower thermal resistance than calculated. This accounts for manufacturing tolerances, aging, and unexpected operating conditions.