Don't Be Misled by Power Device Specs

Focus:

Datasheet specifications for maximum power dissipation for a power semiconductor device can be confusing. For a given device in a given package, sometimes more than one value of maximum power is specified, and the test conditions under which those ratings were obtained are not clearly explained. Some engineers are left wondering what the maximum power rating is for a given package. But as the author explains in this article, the maximum power rating largely depends on external factors in the application such as ambient temperature, the heat contribution from other heat sources, and the thermal resistance from package to ambient. All of these factors combine with the package dependent portion of thermal resistance to determine the maximum power dissipation for a given device. The author explains all this using simple electrical analogies and graphs to illustrate the concepts. Then, he presents a datasheet example to further illustrate how there can be two maximum power ratings for a given device without contradiction.

What you’ll learn:

• How to understand and interpret power device ratings given on datasheets
• How to determine the maximum power dissipation for a power semiconductor device

Notes:

A PDF of the article as it appeared in print is available at http://powerelectronics.com/thermal_management/
thermal_management_simulation/805PET21pow er-device-speed.pdf

View the Source

Author & Publication:

Roger Stout, Senior Research Scientist, ON Semiconductor, Technology Development, Advanced Packaging, Phoenix, Power Electronics Technology, May 01 2008

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