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How to Calculate Maximum Case Temperature of a Device

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Last updated Dec 21, 2023 | Published on Jun 11, 2019

Gathering Critical Device Data

Finding how much heat your electronic device dissipates and how to calculate maximum case temperature can be difficult if you’re not sure what you’re looking for. But determining the amount of heat a device dissipates is one of the first and most critical steps to developing the right thermal management solution.

The device you are using in your application will typically have an extensive datasheet that accompanies your purchase or is available from the manufacturer. Most electronic device manufacturers make this information freely available to customers or prospective customers. However, sometimes you may need to hunt for information. You usually can find it from either the manufacturer or the vendor you purchased your devices from.

Key Datasheet Terms

Most of the key values you’re looking for in determining the maximum heat load and power dissipation of your device are in the Thermal section. In general, device datasheets will indicate:

Power Dissipation (W)

Maximum Junction Temperature (Tj-max, commonly in °C)

Junction-to-Case Thermal Resistance (Ɵjc, generally °C/W)

As these datasheets are often written with the electrical engineer as the primary user; critical thermal information might not be easy to find. In some cases, figuring out what your datasheet is saying can be difficult as different manufacturers may represent the same information in different formats or locations. In case you still can’t find these values after scouring the table of contents or all the sections, reach out to the device manufacturer as these are important values to have before your start designing.

Calculating Max Case Temperature

In order to calculate your maximum case temperature, first multiply the amount of heat the device dissipates by the junction-to-case thermal resistance to get the temperature rise from junction to case. Then subtract this temperature rise from the maximum junction temperature to get the maximum case temperature.

Tjunction-max – (Ɵjunction-to-case*Pdissipated) = Tcase-max

This calculation may not always so straightforward, as in the case of Thermoelectric Coolers (TECs) or Thermoelectric Devices (TEDs). Because they have a “hot side” and a “cold side,” it may take a couple of calculations to determine how your device handles heat on both sides.

Next Steps in Thermal Management Design

If you need assistance, please don’t hesitate to contact our Engineering Team. They’ve had extensive experience in reading these types of datasheets and can help you design the right solution for you.

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