u-blox SARA-G3 Series User Manual

SARA-G3 series - System Integration Manual
UBX-13000995 - R06 Objective Specification Design-in
Page 155 of 218
2.11 Thermal guidelines
SARA-G3 series module operating temperature range and module thermal resistance are specified in
the SARA-G3 series Data Sheet [1].
The most critical condition concerning module thermal performance is the uplink transmission at maximum
power (data upload or voice call 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 SARA-G3 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 (Rth,M-A) depends on the module operating
condition (e.g. GSM or GPRS mode, transmit band): 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 SARA-G3 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
8
, the increase of the module temperature
9
in different modes of
operation, referred to idle state initial condition
10
, can be summarized as following:
 ~8 °C during a GSM voice call (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 SARA-G3 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 via stack down to main ground layer
8
Refer to SARA-G3 series Data Sheet [1] for the Rth,M-A value in this application condition
9
Temperature is measured by internal sensor of wireless module
10
Steady state thermal equilibrium is assumed. The module’s temperature in idle state can be considered equal to ambient
temperature

u-blox SARA-G3 Series Specifications

General

Brand	u-blox
Model	SARA-G3 Series
Category	GSM/GPRS Modules
Language	English