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2.10 Thermal guidelines
TOBY-L1 series module operating temperature range and module thermal resistance are specified in the
TOBY-L1 series Data Sheet [1].
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; however the application should be correctly designed to cope with it.
During transmission at maximum RF power the TOBY-L1 series modules generate thermal power that can exceed
1 W: this is an indicative value since the exact generated power strictly depends on operating condition such as
the number of allocated TX slot, 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
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.
Mounting a TOBY-L1 series module on a 79 mm x 62 mm x 1.41 mm 4-Layers PCB with a high coverage of
copper in still air conditions
to idle state initial condition
~8 °C during a LTE connection (1 TX slot, 1 RX slot) at max TX power
~12 °C during a GPRS data transfer (2 TX slots, 3 RX slots) at max TX power
The Module-to-Ambient thermal resistance value and the relative increase of module temperature will be
different for other mechanical deployments of the module, e.g. PCB with different dimensions and
characteristics, mechanical shells enclosure, or forced air flow.
The increase of thermal dissipation, i.e. the Module-to-Ambient thermal resistance reduction, will decrease the
temperature for internal circuitry of TOBY-L1 series modules for a given operating ambient temperature. This
improves the device long-term reliability for applications operating at high ambient temperature.
A few hardware techniques may be used to reduce the Module-to-Ambient thermal resistance 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 complete thermal via stacked down to 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 application 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.
Force ventilation air-flow within 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 wireless module.
1
Refer to TOBY-L1 series Data Sheet [1] for the R
2
Temperature is measured by internal sensor of wireless module
3
Steady state thermal equilibrium is assumed. The module's temperature in idle state can be considered equal to ambient temperature
UBX-13001482
1
, the increase of the module temperature
3
, can be summarized as following:
value in this application condition
th,M-A
Objective Information
TOBY-L1 series - System Integration Manual
) depends on the module operating
th,M-A
2
in different modes of operation, referred
Design-in
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