LG KG270, Service Manual

Page: 22 / 125

3. TECHNICAL BRIEF
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RF input and output ports of the SKY77318 are internally matched to a 50
Ω
load to reduce the
number of external components for a quad-band design. Extremely low leakage current (2.5
µ
A,
typical) of the dual PA module maximizes handset standby time. The SKY77318 also contains
bandselect switching circuitry to select GSM (logic 0) or DCS/PCS (logic 1) as determined from the
Band Select (BS) signal.
In Figure 1 below, the BS pin selects the PA output (DCS/PCS_OUT orGSM_OUT) and the Analog
Power Control (VAPC) controls the level of output power.
The VBATT pin connects to an internal current-sense resistor and interfaces to an integrated power
amplifier control (iPAC

) function, which is insensitive to variations in temperature, power supply,
process, and input power.
The ENABLE input allows initial turn-on of PAM circuitry to minimize battery drain.