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Device Datasheets: Power Dissipation and How to Calculate Max Case Temperature

Last updated Dec 21, 2023 | Published on Jul 16, 2018

Extracting input information from device datasheets is the first step in determining your thermal requirements for your application

Gathering Critical Data for Designing Thermal Management

Finding how much heat your electronic device dissipates and how to calculate max case temperature can sometimes be a pain. 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 are good about making this information available. Other times, you might need to chase down some of this information. You usually can find it from either the manufacturer or the vendor you purchased your devices from.

Terms You’re Looking for in your Datasheet

Generally, these datasheets indicate: power dissipation (W), the maximum junction temperature (commonly °C), and a junction-to-case thermal resistance (generally °C/W) in the “Thermal” section. Hopefully the device manufacturer was kind enough to indicate where this block of information is in the table of contents or made it pop, since this information likes to hide away.

The Actual Math Part: Calculate 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 the 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

In some cases, figuring out what your datasheet is saying can be a trying ordeal. Thermoelectric Coolers (TECs) or Thermoelectric Devices (TEDs) can be doubling confusing since there is a “hot side” and a “cold side,” and the control of both sides is critical to function.

Multiple Devices or System Heat Loads

If you have multiple devices or an existing system that you want to cool together, you may want to test your thermal load instead of calculating, especially for retrofit situations.

If All Else Fails

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

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