RF3108PCBA-41X RFMD [RF Micro Devices], RF3108PCBA-41X Datasheet - Page 5

• Manufacturer Part Number: RF3108PCBA-41X
• Description: TRIPLE-BAND GSM/DCS/PCS POWER AMP MODULE
• Manufacturer: RFMD [RF Micro Devices]

The RF3108 is a triple-band, GSM/DCS/PCS power
amplifier with two separate RF inputs and outputs that
are internally matched to 50Ω. Pins 2 and 14 of the
device provide the RF input and output for the
DCS/PCS band, which is optimized for performance
between 1710MHz and 1910MHz. Pins 5 and 8 of the
device provide the RF input and output for the GSM
band, which is optimized for performance between
880MHz and 915MHz. Both bands include an internal
DC-blocking capacitor to protect the device from exter-
nal DC source inputs and block internal DC from exit-
ing the inputs and outputs of the module. The
performance is similar to the performance of the
RF2173 and RF2174 MIMIC devices used in dual- or
triple-band applications. However, the RF3108 module
includes the matching and bypass capacitors required
for operation internal to the 9mmx10mm module. How-
ever, some external components are required to
improve stability, isolation and noise power perfor-
mance. These components are included on the evalua-
tion board and schematic, and will be described in the
following paragraphs.
The GSM 900MHz band provides 32dB and the
DCS/PCS 1710MHz to 1910MHz band provides 28dB
of small signal gain at full output power. Therefore, the
drive level required to fully saturate the output is
+4dBm for each band. Based upon HBT (Heterojunc-
tion Bipolar Transistor) technology, the part requires
only a single positive 3V supply to operate to full spec-
ification. The DCS/PCS band input is located at pin 2
of the device and requires no external components.
The GSM 900MHz band input is located at pin 6 of the
device and also does not require external components.
However, a 180Ω resistor is included at the input of the
GSM band to improve the input impedance and isola-
tion performance at low V
both high and low bands are internally matched to 50Ω
at the output of pin 14 and 8. A 50Ω microstrip should
be used to interface to the input and output connec-
tions.
Rev A7 051003
Theory of Operation and Application Information
APC
levels. The output for
Power control for the GSM 900MHz band is provided
through pin 5 of the device, and pin 3 for the DCS/PCS
band. The V
bypass capacitors and will require some external filter-
ing. Because the V
the device, the user has the option of choosing a
capacitor value that meets the control loop BW and fil-
tering requirement for various applications. In most typ-
ical applications with a closed loop power control, the
recommended bypass capacitor for this input is
approximately 33pF for the GSM band, and 12pF for
the DCS/PCS band. However in open loop operation, a
10nF V
bands to filter noise from the external V
10nF capacitor is installed on pins 3 and 5 on the cur-
rent evaluation board (see the evaluation board sche-
matic). Noise on the V
power performance of the device, so care should be
used to provide a clean V
cially important when measuring noise power or stabil-
ity performance.
The voltage supply V
capacitors and inductors to filter unwanted noise on
the DC supply voltage. However, the main V
the device at pin 11 requires some additional bypass
capacitors as shown in the evaluation board sche-
matic. C5 (1uF) and C4 (3.3uF) are required to
improve the stability performance.
All the internal ground connections are connected to a
series of ground pads located on the backside of the
package as shown in the pin out diagram. Pins 4, 9,
10, 12, and 13 are also ground connections. The final
stages of both bands are connected to the ground
pads on the backside of the package. Therefore this
ground connection is essential to dissipate heat and to
provide proper current flow. Refer to the evaluation
board layout as an example of the vias locations and
quantity required for proper connection.
APC
bypass capacitor is recommended for both
APC
inputs do not contain any internal
APC
APC
filtering capacitor is external to
CC
APC
input will degrade the noise
contains internal bypass
input signal. This is espe-
RF3108
APC
CC
source. A
input to
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