Telit Wireless Solutions GE863-QUAD - Manual (Page 20)

GE863-QUAD
GE863-PY
1vv0300715 Rev. 1 - 19/09/06
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Right reserved page 20 of 79
As you can see, the charging process is not a trivial task to be done; moreover all these operations
should start only if battery temperature is inside a charging range, usually 5°C - 45°C.
The GE863-QUAD/PY measures the temperature of its internal component, in order to satisfy this last
requirement, it's not exactly the same as the battery temperature but in common application the two
temperature should not differ too much and the charging temperature range should be guaranteed.
NOTE: For all the threshold voltages, inside the GE863-QUAD/PY all threshold are fixed in
order to maximize Li-Ion battery performances and do not need to be changed.
NOTE: In this application the battery charger input current must be limited to less than
400mA. This can be done by using a current limited wall adapter as the power source.
4.2.2 Thermal Design Guidelines
The thermal design for the power supply heat sink should be done with the following specifications:
• Average current consumption during transmission @PWR level max (rms):
500mA
• Average current consumption during transmission @ PWR level min (rms): 100mA
• Average current during Power Saving: 4mA
• Average current during idle (Power Saving disabled) 19mA
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
500mA 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 500mA, 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 GE863-QUAD/PY, you can consider it to be during transmission 1W
max during CSD/VOICE calls and 2W max during class10 GPRS upload.
This generated heat will be mostly conducted to the ground plane under the GE863-QUAD/PY; you
must ensure that your application can dissipate it.