Motorola Confidential Proprietary
V975/V980Theory of Operation
3-12
Draft 1.0
WCDMA PA (U850)
Durango5W is a three-stage power amplifier handling
the band of WCDMA Tx frequencies between 1920 –
1980MHz. The nominal expected maximum gain is
~30dB.
A Motorola proprietary high power / low power effi-
ciency enhancement load switch (5W_VLD) is included
in the output match. VLD adjusts the output load for
optimum efficiency from low power to high power out.
In conjunction with VLD, bias control
(WB_PA_VBA1/WB_PA_VBA2) is performed be-
tween high and low power ranges.
The amplified WCDMA carrier is fed into a RF cou-
pler device which has an integrated RF detector. An
RF detect will pass through the Durango 9E3G (GSM
PA) before being fed to the Harmony for power detec-
tion.
U880 is used to measure temperature. Its linear output
is a voltage signal that corresponds to its physical de-
vice temperature. TEMP_SENSE is measured by
PCAP and the MCU (POG) retreives the temperature
readings every 5 seconds and passes it to the DSP
(POG) so that the temperature compensation tables are
updated.
The isolator provides a stable 50 ohm PA load. It also
protects the PA from interfering with other frequency
bands. Finally, it guards against IM products being pro-
duced by the transmitter and affecting receiver circuits.
Figure 3-15. Durango 5W (WCDMA PA)
WCDM A PA
FL40
MatchMatch
Bias
Control
Load
Control
Adj
Match
Final
Match
Driver
Pre-
Drv
RF WCDMA Transmitter
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