LG KG270 Service Manual - Page 22

Band Select BS signal.

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3. TECHNICAL BRIEF 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 µA, 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. - 23 -

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3. TECHNICAL BRIEF
- 23 -
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.