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3. TECHNICAL BRIEF
3.1 Power Amplifier (SKY77318, U600)
The SKY77318 Power Amplifier Module (PAM) is designed in a low profile (1.2 mm), compact form
factor for quad-band cellular handsets comprising GSM850/900, DCS1800, and PCS1900 operation.
The PAM also supports Class 12 General Packet Radio Service (GPRS) multi-slot operation. The
module consists of separate GSM850/900 PA and DCS1800/PCS1900 PA blocks,
impedancematching circuitry for 50 Ω input and output impedances, and a Power Amplifier Control
(PAC) block with an internal current-sense resistor. The custom BiCMOS integrated circuit provides
the internal PAC function and interface circuitry. Fabricated onto a single Gallium Arsenide (GaAs) die,
one Heterojunction Bipolar Transistor (HBT) PA block supports the GSM850/900 bands and the other
supports the DCS1800 and PCS1900 bands. Both PA blocks share common power supply pins to
distribute current. The GaAs die, the Silicon (Si) die, and the passive components are mounted on a
multi-layer laminate substrate. The assembly is encapsulated with plastic overmold. 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 band-select 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 or GSM850/900 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. Figure 1.
Functional Block Diagram
Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
Figure1. Functional Block Diagram
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3. TECHNICAL BRIEF
LGE Internal Use Only
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