How to choose the correct 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.

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

How to use thermal curves in our technical data sheets

On peut directement déterminer le type de dissipateur à utiliser en fonction du courant commuté et de la température ambiante.

Exemple Ieff = 6 Ampères et température ambiante maxi = 38°C

Operating mode of the above curves:

  • identify the current to switch on the abscissa of the left-hand curve
  • plot a vertical line from the above point up to the curve (1)
  • from the obtained point, a horizontal line is plotted to the right-hand curve (2)
  • identify the ambient temperature on the abscissa of the right-hand curve
  • plot a vertical line from this point until you reach the horizontal line previously plotted (3)
  • this point determines the type of heatsink to use
  • 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)

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