MiscEl: Heatsink

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This page is used to calculate heatsinks, it can handle up to 6 heat sources on a single heatsink.
Heatsink calculations models the path from the junction (inside the chip/transistor) where heat is generated, to the air. This path is usual split in 3 parts.
  1. From the junction to the case of the component, this value is found in the datasheet for the component.
  2. From the case of the component to the heatsink, this value must be estimated and this estimate depends on how the component is mounted to the heatsink.
  3. From the heatsink to the air, this value is in the datasheet for the heatsink

Input values

PowerThe power dissipated in the component
Rth j-cInternal heat resistance of the component, see datasheet for component
Interface to heatsinkHow the component is mounted on the heatsink
PackageUsed to determine the surface between the component and the heatsink
Rth c-hHeat resistance of interface
Air temperatureAir temperature around heatsink, this will typical 10-20 degrees above max. expected room temperature
Heatsink Rth h-aHeat resistance of heatsink

Interface to heatsink

Rth ch=0No heat resistance
Rth c-hSpecify your own heat resistance
Rth c-h for 1 cm²Specify your own heat resistance
Rth c-h for 1 inch²Specify your own heat resistance, this setting is used for most terminal interface pads
Direct mounting, dryA typical value for dry mounting on a heatsink
Direct mounting, greaseA typical value for mounting with grease on a heatsink
all otherThese are pads that can be used between the component and the heatsink to give a good thermal interface and in some cases also electric isolation

Output values

Heatsink temperatureAverage temperature of the heatsink
Total powerThe sum of power settings on panel #1 to #6
Max. junction temp.The highest junction temperatur from panel #1 to #6
Component #xData from the specified panel
Rth j-cSpecified value
Thermal interfaceSelected thermal interface
Rth c-hCalculated heat resistance between case and heatsink
Temp. (junction)Junction temperature of component on this pane
Interface to hot This warning is shown for some of the predefined terminal pads, when the temperature is above their specified limit


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