HE910 Hardware User Guide
1VV0300925 Rev. 32 Page 47 of 111 2019-11-25
5.3.2. Thermal Design Guidelines
The thermal design for the power supply heat sink should be done with the following
specifications:
• Average current consumption during HSDPA transmission @PWR level max :
600 mA
• Average current during idle:
1.5 mA
NOTE:
The average consumption during transmissions depends on the
power level at which the device is requested to transmit by the
network. The average current consumption hence varies significantly.
Considering the very low current during idle, especially if Power Saving function is
enabled, it is possible to consider from the thermal point of view that the device absorbs
current significantly only during calls.
If we assume that the device stays into transmission for short periods of time (let's say few
minutes) and then remains for a quite long time in idle (let's say one hour), then the power
supply has always the time to cool down between the calls and the heat sink could be
smaller than the calculated one for 600mA maximum RMS current, or even could be the
simple chip package (no heat sink).
Moreover in the average network conditions the device is requested to transmit at a lower
power level than the maximum and hence the current consumption will be less than the
600mA, being usually around 150mA.
For these reasons the thermal design is rarely a concern and the simple ground plane
where the power supply chip is placed can be enough to ensure a good thermal condition
and avoid overheating.
For the heat generated by the HE910, you can consider it to be during transmission 1W
max during CSD/VOICE calls and 2W max during GPRS upload.
This generated heat will be mostly conducted to the ground plane under the HE910; you
must ensure that your application can dissipate it.
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