User's Manual

LISA-U1/LISA-H1 series - System Integration Manual
3G.G2-HW-10002-2 Advance Information Design-In
Page 95 of 116
2.3 Thermal aspects
The operating temperature range is specified in the LISA-U1/LISA-H1 series Data Sheet [1].
The most critical condition concerning 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 LISA-U1/LISA-H1 series modules generate thermal power that
can exceed 2 W: this is an indicative level since the exact generated power strictly depends on operating
condition such as the number of allocated TX slot and modulation (GMSK or 8PSK) or data rate (WCDMA),
transmitting frequency band, etc. The generated thermal power must be adequately dissipated through the
thermal and mechanical design of the application.
The increase of thermal dissipation, i.e. reducing the thermal resistance, will reduce the operating temperature
for internal circuitry of LISA-U1/LISA-H1 series modules for the same operating ambient temperature. This
improves the device long-term reliability for applications operating at high ambient temperature.
A few techniques may be used to reduce the thermal resistance in the application:
 Forced ventilation air-flow within mechanical enclosure
 Usage of thermal transfer material (e.g. greases and pastes)
 Heat sink attached to the module top side, with electrically insulated / high thermal conductivity adhesive
 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