User's Guide
HE863 Family Hardware User Guide
1vv0300891 Rev.5
- 2011-03-18
Reproduction forbidden without Telit Communications S.p.A’s. written authorization - All Rights
Reserved. Page 43 of 89
6.2.2. Thermal Design Guidelines
The thermal design for the power supply heat sink must be done
with the following specifications:
Average current consumption during WCDMA/HSPA
transmission @PWR level max : 710mA
Average current consumption during class12 GPRS
transmission @PWR level max : 670mA
Average GPS current during GPS ON (Power Saving
disabled) in HE863-EUG/NAG/AUG : 55mA
NOTE:
The average consumption during transmissions depends on the
power level at which the device is requested to transmit via
the network. The average current consumption hence varies
significantly.
NOTE:
The thermal design for the Power supply must be made keeping
an average consumption at the max transmitting level during
calls of 750mA rms plus 100mA rms for GPS in tracking mode in
HE863-EUG/NAG/AUG.
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 in transmission for short
periods of time (let us say few minutes) and then remains for
quite a long time in idle (let us 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
for 850mA maximum RMS current. There could even be a simple
chip package (no heat sink).
Moreover in 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 850mA (TBD, 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 HE863 Family, you can consider
it to be during transmission 1W max during CSD/VOICE calls and