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How to choose the right heatsink

The switching device must be sufficiently cooled so that the junction temperature does not exceed the required values: usually 125 or 150°C (this value depends on the power components) and so that the temperature of the heatsink does not exceed 90 or 100°C.

The heatsink can be determined either by calculation (see technical note - pages 4 to 6) or directly from the curves provided by celduc.

How to use thermal curves in our technical data sheets

choose the right heatsink

The type of heatsink to use can be determined by the switched current and the ambient temperature.

Example Ieff = 6 A and max. ambient temperature = 38°C

Operating mode of the above curves:

1- identify the current to switch on the abscissa of the left-hand curve

2- plot a vertical line from the above point up to the curve (1)

3- from the obtained point, a horizontal line is plotted to the right-hand curve (2)

4- identify the ambient temperature on the abscissa of the right-hand curve

5- plot a vertical line from this point until you reach the horizontal line previously plotted (3)

6- this point determines the type of heatsink to use

7- select the heatsink corresponding to the curve located above this point. In this example 1.2°/W (4)

You can see that for a 1.2°/W, 6A heatsink, the ambient temperature should not exceed 54°C (8) (9)
And a 1.2°/W heatsink in a 38°C ambient temperature, the maximum current can reach up to 8A 
(5) (6) (7)

To have access to our complete range of heatsinks - click here

Also refer to:
Thermal Pads or Thermal Paste – Differences and Advantages