Installation Instructions

LISA-U2 series - System Integration Manual
UBX-13001118 - R19 Early Production Information Design-In
Page 127 of 175
Further hardware techniques to be used to improve heat dissipation in the application:
 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 cellular module, as a large part
of the heat is transported through the GND pads and dissipated over the backside of the application board
For example, after the installation of a robust aluminum heat-sink with forced air ventilation on the back of the
same application board described above, the Module-to-Ambient thermal resistance (Rth,M-A) is reduced to
1.5 ÷ 3.5 °C/W. The effect of lower Rth,M-A can be seen from the module temperature increase, which now can
be summarized as following:
 1.5°C during a GSM voice call at max TX power
 3°C during GPRS data transfer with 4 TX slots at max TX power
 2.5°C during EDGE data transfer with 4 TX slots at max TX power
 5.5°C in UMTS/HSxPA connection at max TX power
Beside the reduction of the Module-to-Ambient thermal resistance implemented by the hardware design of the
application device integrating a LISA-U2 module, the increase of module temperature can be moderated by the
software implementation of the application.
Since the most critical condition concerning module thermal power occurs when module connected mode is
enabled, the actual module thermal power depends, as module current consumption, on the radio access mode
(GERAN / UTRA), the operating band and the average TX power.
A few software techniques may be implemented to reduce the module temperature increase in the application:
 Select the radio access mode which provides lower temperature increase (see the module temperature
increase values summarized above) by means of AT command (see the u-blox AT Commands Manual [2],
+COPS command)
 Select the operating band which provides lower current consumption in the selected radio access mode (see
current consumption values reported in the LISA-U2 series Data Sheet [1]) by means of AT command (see
the u-blox AT Commands Manual [2], +UBANDSEL command)
 Enable module connected mode for a given time period and then disable it for a time period enough long to
properly mitigate temperature increase