NE866B1_Hardware_Design_Guide
1VV0301354 Rev. 6
Page
26
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2018-02-28
4.3.2.
Thermal Design Guidelines
The thermal design for the power supply heat sink should be done with the following
specifications:
•
Average current consumption during NB-IoT transmission @ Max PWR level at min
battery level :
195 mA
•
Average current during idle:
5.3 mA
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 300mA 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
195mA (@23dBm), being usually around
150
mA (@20dBm).
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.
The generated heat will be mostly conducted to the ground plane under the NE866B1; you
must ensure that your application can dissipate it.
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.