220.127.116.11. Not Using a Heat Sink
- From the device through the case to the air
- From the device through the board to the air
In the model used in the Early Power Estimator (EPE) spreadsheet, power is dissipated through the case and board. The θJA values are calculated for differing air flow options accounting for the paths through the case and through the board.
The ambient temperature does not change, but the junction temperature changes depending on the thermal properties; therefore the junction temperature calculation is an iterative process.
The following equation shows the total power calculated based on the total θJA value, ambient, and junction temperatures.
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