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WSW Components Line of Board-Level Transistor Heat Sink Overview Slide 10

Thermal resistance needs to be calculated in order to choose the proper heat sink to keep the component operating at a safe temperature. Once the Max ambient Temperature is known as well as the Max Component Temperature and Component Power, which is typically given on the device manufacturer’s data sheet, the designer can use the formula shown here to calculate the maximum allowable heat sink resistance. A heat sink can then be selected which will provide no more than this value of thermal resistance. Keep in mind, this formula is in its most simplistic form, there are other considerations that can be taken into account. For this example, subtract the maximum ambient temperature from the maximum component temperature to get the delta temperature which is the heat sink temperature rise above ambient. Then divide this delta temperature by the component power rating to get a maximum heat sink thermal resistance value of 10 °C/W.

PTM Published on: 2013-05-06