LENA-R8 series - System integration manual
UBX-22015376 - R02
Design-in
Page 93 of 116
C1-Public
2.15
Thermal guidelines
☞
Modules’ operating temperature range
is specified in the LENA-R8 series data sheet
The most critical condition concerning module thermal performance is the uplink transmission at
maximum power (data upload in connected mode), when the baseband processor runs at full speed,
radio circuits are all active and the RF power amplifier is driven to higher output RF power. This
scenario is not often encountered in real networks (for example, see the Terminal Tx Power
distribution for WCDMA, taken from operation on a live network, described in the GSMA TS.09 Battery
Life Measurement and Current Consumption Technique
); however the application should be
correctly designed to cope with it.
During transmission at maximum RF power, the LENA-R8 series modules generate thermal power
that may exceed 2 W: this is an indicative value since the exact generated power strictly depends on
operating condition such as the actual antenna return loss, the number of allocated TX resource
blocks, the transmitting frequency band, etc. The generated thermal power must be adequately
dissipated through the thermal and mechanical design of the application.
The spreading of the Module-to-Ambient thermal resistance (R
th,M-A
) depends on the module
operating condition. The overall temperature distribution is influenced by the configuration of the
active components during the specific mode of operation and their different thermal resistance
toward the case interface.
☞
The Module-to-Ambient thermal resistance value and the relative increase of module temperature
will differ according to the specific mechanical deployments of the module, e.g. application PCB
with different dimensions and characteristics, mechanical shells enclosure, or forced air flow.
The increase of the thermal dissipation, i.e. the reduction of the Module-to-Ambient thermal
resistance, will decrease the temperature of the modules’ internal circuitry for a given operating
ambient temperature. This improves the device long-term reliability in particular for applications
operating at high ambient temperature.
Recommended hardware techniques to be used to improve heat dissipation in the application:
•
Connect each
GND
pin with solid ground layer of the application board and connect each ground
area of the multilayer application board with a complete thermal via stacked down to the main
ground layer.
•
Provide a ground plane as wide as possible on the application board.
•
Optimize antenna return loss, to optimize overall electrical performance of the module including a
decrease of module thermal power.
•
Optimize the thermal design of any high-power components included in the application, such as
linear regulators and amplifiers, to optimize overall temperature distribution in the device.
•
Select the material, the thickness and the surface of the box (i.e. the mechanical enclosure) of the
application device that integrates the module so that it provides good thermal dissipation.
Further HW techniques that may be considered to improve the heat dissipation in the application:
•
Force ventilation air-flow within the mechanical enclosure.
•
Provide a heat sink component attached to the module top side, with electrically insulated / high
thermal conductivity adhesive, or on the backside of the application board, below the cellular
module, as a large part of the heat is transported through the GND pads of the LENA-R8 series
LGA modules and dissipated over the backside of the application board.
For example, the Module-to-Ambient thermal resistance (R
th,M-A
) is strongly reduced with forced air
ventilation and a heat-sink installed on the back of the application board, decreasing the module
temperature variation.
