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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.
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)