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MRFIC0913 Datasheet(PDF) 6 Page - Motorola, Inc

Part No. MRFIC0913
Description  900 MHz GSM CELLULAR INTEGRATED POWER AMPLIFIER GaAs MONOLITHIC INTEGRATED CIRCUIT
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Maker  MOTOROLA [Motorola, Inc]
Homepage  http://www.freescale.com
Logo MOTOROLA - Motorola, Inc

MRFIC0913 Datasheet(HTML) 6 Page - Motorola, Inc

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MRFIC0913
6
MOTOROLA RF DEVICE DATA
APPLICATIONS INFORMATION
Design Philosophy
The MRFIC0913 is a two–stage Integrated Power Amplifier
designed for use in cellular phones, especially for those used
in GSM Class IV, 4.8 V operation. With matching circuit modifi-
cations, it is also applicable for use in GSM Class IV 6 V and
Class V 3.6 V equipment. Due to the fact that the input, output
and some of the interstage matching is accomplished off chip,
the device can be tuned to operate anywhere within the 800 to
1000 MHz frequency range. Typical performance at different
battery voltages is:
S
36.0 dBm @ 5.8 V
S
35.0 dBm @ 4.8 V
S
31.5 dBm @ 3.6 V
This capability makes the MRFIC0913 suitable for portable
cellular applications such as:
S
6 and 4.8 V GSM Class IV
S
3.6 V GSM Class V
S
3.6 V, 1.2 W Analog Cellular
RF Circuit Considerations
The MRFIC0913 can be tuned by changing the values and/
or positions of the appropriate external components. Refer to
Figure 2, a typical GSM Class IV applications circuit.
The input match is a shunt–C, series–L, low–pass structure
and can be retuned as desired with the only limitation being
the on–chip 12 pF blocking capacitor. For saturated applica-
tions such as GSM and analog cellular, the input match should
be optimized at the rated RF input power.
Interstage matching can be optimized by changing the val-
ue and/or position of the decoupling capacitor on the VD1 sup-
ply line. Moving the capacitor closer to the device or reducing
the value increases the frequency of resonance with the in-
ductance of the device’s wirebonds and leadframe pin.
Output matching is accomplished with a one–stage low–
pass network as a compromise between bandwidth and har-
monic rejection. Implementation is through chip capacitors
mounted along a 30 or 50
Ω microstrip transmission line. Val-
ues and positions are chosen to present a 3
Ω loadline to the
device while conjugating the device output parasitics. The net-
work must also properly terminate the second and third har-
monics to optimize efficiency and reduce harmonic output.
When low–Q commercial chip capacitors are used for the
shunt capacitors, loss can be reduced by mounting two ca-
pacitors in parallel, as shown in Figure 2, to achieve the total
value needed.
Loss in circuit traces must also be considered. The output
transmission line and the bias supply lines should be at least
0.6 mm in width to accommodate the peak circulating currents
which can be as high as 2 amperes. The bias supply line
which supplies the output should include an RF choke of at
least 8 nH, surface mount solenoid inductors or equivalent
length of microstrip lines. Discrete inductors will usually give
better efficiency and conserve board space.
The DC blocking capacitor required at the output of the de-
vice is best mounted at the 50
Ω impedance point in the circuit
where the RF current is at a minimum and the capacitor loss
will have less effect.
Biasing Considerations
Gate bias is supplied to each stage separately through resis-
tive division of the VSS voltage. The top of each divider is brought
out through pins 12 and 13 (VG2 and VG1 respectively) allowing
gate biasing through use of external resistors or positive volt-
ages. This allows setting the quiescent current of each stage
separately.
For applications where the amplifier is operated close to
saturation, such as GSM and analog cellular, the gate bias
can be set with resistors. Variations in process and tempera-
ture will not affect amplifier performance significantly in these
applications. The values shown in the Figure 1 will set quies-
cent currents of 80 to 160 mA for the first stage and 400 to 800
mA for the second stage.
For linear modes of operation which are required for PDC,
DAMPS and CDMA, the quiescent current must be more
carefully controlled. For these applications, the VG pins can be
referenced to some tunable voltage which is set at the time of
radio manufacturing. Less than 1.25 mA is required in the di-
vider network so a DAC can be used as the voltage source.
Typical settings for 6 V linear operation are 100 mA
±5% for
the first stage, and 500 mA
±5% for the second stage.
Power Control Using the MC33169
The MC33169 is a dedicated GaAs power amplifier support
IC which provides the –4 V required for VSS, an N–MOS drain
switch interface and driver and power supply sequencing. The
MC33169 can be used for power control in applications where
the amplifier is operated in saturation since the output power
in non–linear operation is proportional to VD2. This provides a
very linear and repeatable power control transfer function.
This technique can be used open–loop to achieve 20–25 dB
dynamic range over process and temperature variation. With
careful design and selection of calibration points, this tech-
nique can be used for GSM phase II control where 29 dB dy-
namic range is required, eliminating the need for the
complexity and cost of closed–loop control.
The transmit waveform ramping function required for sys-
tems such as GSM can be implemented with a simple Sallen
and Key filter on the MC33169 control loop. The amplifier is
then ramped on as the VRAMP pin is taken from 0 V to 3 V. To
implement the different power steps required for GSM, the
VRAMP pin is ramped between 0 V and the appropriate voltage
between 0 V and 3 V for the desired output power.
For closed–loop configurations using the MC33169,
MMSF4N01HD N–MOS switch and the MRFIC0913 provide a
typical 1 MHz 3 dB loop bandwidth. The STANDBY pin must
be enabled (3 V) at least 300
µs before the VRAMP pin goes
high and disabled (0 V) at least 20
µs before the VRAMP pin
goes low. This STANDBY function allows for the enabling of
the MC33169 one burst before the active burst thus reducing
power consumption.
Conclusion
The MRFIC0913 offers the flexibility in matching circuitry and
gate biasing required for portable cellular applications. Together
with the MC33169 support IC, the device offers an efficient sys-
tem solution for TDMA applications such as GSM where satu-
rated amplifier operation is used.
Evaluation Boards
Evaluation boards are available for RF Monolithic Inte-
grated Circuits by adding a “TF” suffix to the device type.
For a complete list of currently available boards and ones
in development for newly introduced product, please con-
tact your local Motorola Distributor or Sales Office.


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