Only For Training And Service Purposes - LG TU550 Service Manual

3.5.3 UMTS Power Amplifier (U105 : RF5144)
-. U105 : UMTS 850 Power Amplifier module
The RF5144 is a high-power, high-efficiency linear amplifier module specifically designed for 3V
handheld systems. The device is manufactured on an advanced third generation GaAs HBT process,
and was designed for use as the final RF amplifier in 3V UMTS handheld digital cellular equipment,
spread-spectrum systems, and other applications in the 824MHz to 849MHz band and 1850MHz to
1910MHz band. The RF5144 has a digital control line for low power applications to lower quiescent
current.
3.5.4 Thermistor (R1024 : 68K_2012_10%)
This thermistor senses temperature variations around UMTS PA to adjust PA gain deviation for assure
compliance with the applicable transmit power control standards. Negative temperature compensation
thermistor is used in the TU550.
3.5.5 UMTS transmit power detector (U107 : LMV232TLX)
This detector couples PA output power level to calibrate the transmitter characteristic over the channel
variation and temperature. Its detector coupling range and converted voltage is based on diode
sensitivity and transmitter power level.
The TU550 uses National Semiconductor LMV232TLX power detector IC. In Figure 3.5.5-1, RF input
power range of the device has been optimized for use with a 20dB directional coupler, without the
need for additional external componets. The device has two digital interfaces. A Shutdown function is
available to set the device in a low-power shutdown mode. In case SD=High, the device is in
shutdown, if SD=LOW the device is active.The Band-Select function controls the selection of the active
RF input channel. In case BS=HIGH, Rfin1 is active. In case BS=LOW, Rfin2 is active.
Figure 3.5.5-1 Block diagram of LMV232TLX with Coupler
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Only for training and service purposes

3. TECHNICAL BRIEF
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LGE Internal Use Only