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3. TECHNICAL BRIEF
3.17.4 GSM PAM (U1004, SKY77336)
SKY77336 Power Amplifier Module (PAM) is designed in a compact form factor for quad-band cellular
handsets comprising GSM850/900, DCS1800 and PCS1900, supporting Gaussian Minimum-Shift Keying
(GMSK) and Polar Enhanced Data for GSM Evolution (EDGE) modulation. Class 12 General Packet Radio
Service (GPRS) multi-slot operation is also supported. The module consists of GSM850/900 PA and
DCS1800/PCS1900 PA blocks, impedance matching circuitry for 50
ȳ
input and output impedances, and
a
Power Amplifier Control (PAC) block.
The custom CMOS integrated circuit provides the internal PAC function and interface circuitry. Fabricated
in InGaP/GaAs, the Heterojunction Bipolar Transistor (HBT) PA blocks support the GSM850/900 bands and
DCS1800/PCS1900 bands. Both PA blocks share common power supply pads to distribute
current. The InGaP/GaAs die, Silicon (Si) controller die, and passive components are mounted on a multi-
layer laminate substrate and the entire assembly is encapsulated with plastic overmold. RF input and
output ports of the SKY77336 are internally matched to a 50
ȳ
load to reduce the number of external
components for a quad-band design. Extremely low leakage current (10
Ɇ
A, typical) of the PAM module
maximizes handset standby time. The SKY77336 also contains band-select switching circuitry to select
GSM (logic 0) or DCS/PCS (logic 1) as determined from the Band Select (BS) signal. See Figure shown
below.