Integration Manual

SARA-R4/N4 series - System Integration Manual
UBX-16029218 - R13 Design-in Page 85 of 119
2.12 Thermal guidelines
☞
☞☞
☞ The module operating temperature range is specified in the SARA-R4/N4 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 (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 [10]); however the application should be correctly
designed to cope with it.
During transmission at maximum RF power the SARA-R4/N4 series modules generate thermal power that may exceed
0.5 W: this is an indicative value since the exact generated power strictly depends on operating condition such as the
actual antenna return loss, 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 PCB and connect each ground area of the multilayer
application PCB 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.
• 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.
Beside the reduction of the Module-to-Ambient thermal resistance implemented by correct application hardware design,
the increase of module temperature can be moderated by a correspondingly correct application software
implementation:
• Enable power saving configuration using the AT+CPSMS command
• Enable module connected mode for a given time period and then disable it for a time period long enough to
adequately mitigate the temperature increase.
2.13 Schematic for SARA-R4/N4 series module integration
2.13.1 Schematic for SARA-R4/N4 series modules
Figure 55 is an example of a schematic diagram where a SARA-R4/N4 series “00”, “01” or “x2” product version is
integrated into an application board using all available module interfaces and functions.