Tx Pa Power Control In Sky77318 - Motorola W208 Manual

W208 Level 3 Circuit Description
impedance-matching circuitry for 50 Ω input and output impedances, and a Power
Amplifier Control (APC SKY77318 Pin 20) block with an internal current-sense resistor.
The amplified RF output signal feeds out of SKY77318 from Pin 15 for high-band and Pin
11 for low-band. The high-band signal enters the T/R Switch SW201 Pin 3, and the
low-band signal enters the Antenna Switch U700 Pin 5. The T/R Switch provides
isolation between the various receiver and transmitter paths as they connect to the RF
switch JP201 Pin 1. For Antenna Switch settings, see Section 1.1: Band Selection.
Figure 11: Power Amplifier and Antenna Switch
2.6 TX PA Power Control in SKY77318 U201
Figure 13 shows the Integrated Power Amplifier Control iPAC) function along with
(
SKY77318 proven quad-band PA architecture and BiCMOS current buffering bias scheme.
The iPAC circuitry generally operates independently of other device subcircuits and serves
to make the RF output power a predictable function of the APC SKY77318 Pin 20 (V )
APC
control voltage over variations in supply, temperature, and process. Top-level
performance specifications, with exception of those directly associated with power control
(or the range of APC control voltage), are not altered by placing the device into internal
closed loop operation with the PAENA (PAC Enable) signal. Thus, the iPAC function of the
SKY77318 can be analyzed separately from the general power amplifier performance.
Service Engineering & Optimization
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