RFMD RF2174PCBA

RF2174
Preliminary
2
3V DCS POWER AMPLIFIER
Typical Applications
• Commercial and Consumer Systems
• 3V DCS1900 (PCS) Cellular Handsets
• Portable Battery-Powered Equipment
• 3V Dual-Band/Triple-Band Handsets
• GPRS Compatible
Product Description
2
Optimum Technology Matching® Applied
Si Bi-CMOS
ü
0.45
0.28
3.75
The RF2174 is a high power, high efficiency power amplifier module offering high performance in GSM or GPRS
applications. The device is manufactured on an advanced
GaAs HBT process, and has been designed for use as
the final RF amplifier in DCS1800/1900 hand-held digital
cellular equipment and other applications in the
1700MHz to 2000MHz band. On-board power control
provides over 65dB of control range with an analog voltage input, and provides power down with a logic "low" for
standby operation. The device is self-contained with 50Ω
input and the output can be easily matched to obtain optimum power and efficiency characteristics. The RF2174
can be used together with the RF2173 for dual-band
operation. The device is packaged in an ultra-small plastic package, minimizing the required board space.
Si BJT
2
GaAs HBT
GaAs MESFET
SiGe HBT
Si CMOS
1
0.80
TYP
0.75
0.50
3.75
+
1
1.60 4.00
12°
1.50 SQ
INDEX AREA 3
3.20
0.75
0.65
4.00
1.00
0.90
0.05
0.00
NOTES:
1 Shaded Pin is Lead 1.
2
Dimension applies to plated terminal and is measured between
0.10 mm and 0.25 mm from terminal tip.
The terminal #1 identifier and terminal numbering convention
3 shall conform to JESD 95-1 SPP-012. Details of terminal #1
identifier are optional, but must be located within the zone
indicated. The identifier may be either a mold or marked
feature.
4
5
Pins 1 and 9 are fused.
Package Warpage: 0.05 max.
Package Style: LCC, 16-Pin, 4x4
Features
GND
VCC2
VCC2
VCC2
2F0
• Single 2.7V to 4.8V Supply Voltage
1
16
15
14
13
• +33dBm Output Power at 3.5V
• 27dB Gain with Analog Gain Control
• 51% Efficiency
AT_EN
2
12
RF OUT
RF IN
3
11
RF OUT
GND1
4
10
RF OUT
• 1700MHz to 1950MHz Operation
9
GND
8
VCC
7
APC2
6
APC1
VCC1
5
Functional Block Diagram
Rev A6 010720
• Supports DCS1800 and PCS1900
Ordering Information
RF2174
RF2174 PCBA
3V DCS Power Amplifier
Fully Assembled Evaluation Board
RF Micro Devices, Inc.
7628 Thorndike Road
Greensboro, NC 27409, USA
Tel (336) 664 1233
Fax (336) 664 0454
http://www.rfmd.com
2-231
POWER AMPLIFIERS
• 3V DCS1800 (PCN) Cellular Handsets
RF2174
Preliminary
Absolute Maximum Ratings
Parameter
POWER AMPLIFIERS
2
Supply Voltage
Power Control Voltage (VAPC)
Enable Voltage (VAT_EN)
DC Supply Current
Input RF Power
Duty Cycle at Max Power
Output Load VSWR
Operating Case Temperature
Storage Temperature
Parameter
Rating
Unit
-0.5 to +6.0
-0.5 to +3.0
-0.5 to +3.0
1500
+13
50
10:1
-40 to +85
-55 to +150
VDC
V
V
mA
dBm
%
Caution! ESD sensitive device.
RF Micro Devices believes the furnished information is correct and accurate
at the time of this printing. However, RF Micro Devices reserves the right to
make changes to its products without notice. RF Micro Devices does not
assume responsibility for the use of the described product(s).
°C
°C
Specification
Min.
Typ.
Max.
Unit
Overall
Operating Frequency Range
Usable Frequency Range
Maximum Output Power
Total Efficiency
Recommended Input Power
Range
Output Noise Power
+32
+31.5
+29.5
45
+5
Forward Isolation
-37
-40
-60
-65
Second Harmonic
Third Harmonic
All Other Non-Harmonic Spurious
Input Impedance
Input VSWR
Output Load VSWR
1710 to 1785
1850 to 1910
1700 to 2000
+33
+32.8
+31.5
+31
+30
51
51
15
10
+7
+9
MHz
MHz
MHz
dBm
dBm
dBm
dBm
dBm
%
%
%
%
dBm
-79
dBm
-30
-35
-45
-50
-36
dBm
dBm
dBc
dBc
dBm
Temp=25 °C, VCC =3.5V, VAPC1,2 =2.6V,
VAT_EN =2.6V, PIN =+6dBm, Freq=1710MHz
to 1910MHz, 25% Duty Cycle, pulse
width=1154µs
See application schematic for tuning details.
A different tuning is required.
Temp=25 °C, VCC =3.5V, VAPC1,2 =2.6V
Temp=+25 °C, VCC =3.2V, VAPC1,2 =2.6V
Temp=+85 °C, VCC =3.2V, VAPC1,2 =2.6V
Temp=25 °C, VCC =2.7V, VAPC1,2 =2.6V
Temp=+85 °C, VCC =2.7V, VAPC1,2 =2.6V
At POUT,MAX, VCC =3.5V
At POUT,MAX, VCC =3.0V
POUT =+20dBm
POUT =+10dBm
RBW=100kHz, 1805MHz to 1880MHz and
1930MHz to 1990MHz,
POUT,MIN <POUT <POUT,MAX,
PIN,MIN <PIN <PIN,MAX, VCC =3.0V to 5.0V
VAPC1,2 =0.2V, PIN =+9dBm
VAPC1,2 =0.2V, PIN =+6dBm
POUT <+32.5dBm
Ω
50
2.2:1
3:1
10:1
Output Load Impedance
Condition
Ω
4.5-j3.9
POUT,MAX-5dB<POUT <POUT,MAX
POUT <POUT,MAX-5dB
Spurious<-36dBm, VAPC1,2 =0.2V to 2.6V,
RBW=100kHz
Load Impedance presented at RF OUT pin
Power Control
Power Control “ON”
2.6
Power Control “OFF”
0.2
0.5
Attenuator Enable “ON”
Attenuator Enable “OFF”
2.5
0.2
2.6
0.5
2-232
V
V
2.85
V
V
Maximum POUT, Voltage supplied to the
input
Minimum POUT, Voltage supplied to the input
For maximum isolation when VAPC is low
For power down mode
Rev A6 010720
RF2174
Parameter
Power Control Range
Specification
Min.
Typ.
Max.
62
Gain Control Slope
APC Input Capacitance
APC Input Current
68
dB
100
4.5
AT_EN Input Current
Turn On/Off Time
Unit
10
5
10
500
10
100
dB/V
pF
mA
µA
µA
µA
ns
4.8
5.5
V
V
V
300
10
10
A
mA
µA
µA
Condition
VAPC1,2 =0.2V to 2.6V, VAT_EN =2.6V,
PIN =+9dBm
POUT =-10dBm to +33dBm
DC to 2MHz
VAPC1,2 =2.6V
VAPC1,2 =0V
VAT_EN =2.6V, VAPC1,2 =0V
VAT_EN =0V, VAPC1,2 =0V
2
Power Supply
Power Supply Voltage
3.5
2.7
Power Supply Current
1.3
50
1
1
Rev A6 010720
Specifications
Nominal operating limits, POUT <+33dBm
With maximum output load VSWR 6:1,
POUT <+33dBm
DC Current at POUT,MAX
Idle Current, PIN <-30dBm
PIN <-30dBm, VAPC1,2 =0.2V
PIN <-30dBm, VAPC1,2 =0.2V, Temp=+85°C
2-233
POWER AMPLIFIERS
Preliminary
RF2174
Pin
1
2
Function
GND
AT_EN
POWER AMPLIFIERS
2
3
RF IN
Preliminary
Description
Interface Schematic
Internally connected to the ground slug.
See pin 15.
Control input for the PIN diode. The purpose of the PIN diode is to
attenuate the RF input drive level when the VAPC is low. This serves
both to reduce the leakage through the device cause by self biasing
when driving with high level at the RF input, as well as to maintain a
good input match when the bias of the input stage is turned off. When
this pin is “high” the PIN diode control is turned on. See the Theory of
Operation for more details.
RF Input. This is a 50Ω input, but the actual impedance depends on the
interstage matching network connected to pin 5. An external DC blocking capacitor is required if this port is connected to a DC path to ground
or a DC voltage.
To PIN
diode
3k Ω
AT_EN
GND1
VCC1
RF IN
PIN
From Attn
control circuit
4
GND1
5
VCC1
6
APC1
GND 1
From Bias
Stages
Ground connection for the pre-amplifier stage. Keep traces physically
See pin 3.
short and connect immediately to the ground plane for best performance. It is important for stability that this pin has it’s own vias to the
groundplane, to minimize any common inductance.
Power supply for the pre-amplifier stage and interstage matching. This See pin 3.
pin forms the shunt inductance needed for proper tuning of the interstage match. Please refer to the application schematic for proper configuration, and note that position and value of the components are
important.
Power Control for the driver stage and pre-amplifier. When this pin is
APC VCC
"low," all circuits are shut off. A "low" is typically 0.5V or less at room
temperature. A shunt bypass capacitor is required. During normal operation this pin is the power control. Control range varies from about 1.0V
for -10dBm to 2.6V for +33dBm RF output power. The maximum power
that can be achieved depends on the actual output matching; see the
application information for more details. The maximum current into this
pin is 5mA when VAPC1 =2.6V, and 0mA when VAPC =0V.
To RF
Stages
GND
GND
7
8
9
10
APC2
VCC
GND
RF OUT
Power Control for the output stage. See pin 6 for more details.
See pin 6.
Power supply for the bias circuits.
See pin 6.
Internally connected to the ground slug.
RF Output and power supply for the output stage. Bias voltage for the
final stage is provided through this wide output pin. An external matching network is required to provide the optimum load impedance.
RF OUT
From Bias
GND
Stages
PCKG BASE
11
12
13
RF OUT
RF OUT
2F0
14
VCC2
2-234
Same as pin 10.
Same as pin 10.
Same as pin 10.
Same as pin 10.
Connection for the second harmonic trap. This pin is internally connected to the RF OUT pins. The bonding wire together with an external
capacitor form a series resonator that should be tuned to the second
harmonic frequency in order to increase efficiency and reduce spurious
outputs.
Same as pin 15.
Same as pin 10.
Rev A6 010720
RF2174
Preliminary
Pin
15
Function
VCC2
Description
Interface Schematic
Power supply for the driver stage and interstage matching. This pin
forms the shunt inductance needed for proper tuning of the interstage
match. Please refer to the application schematic for proper configuration, and note that position and value of the components are important.
VCC2
From Bias
GND2
Stages
VCC2
GND
Rev A6 010720
Same as pin 15.
2
Same as pin 15.
Ground connection for the output stage. This pad should be connected
to the groundplane by vias directly under the device. A short path is
required to obtain optimum performance, as well as to provide a good
thermal path to the PCB for maximum heat dissipation.
POWER AMPLIFIERS
16
Pkg
Base
2-235
RF2174
Preliminary
Theory of Operation and Application Information
POWER AMPLIFIERS
2
The RF2174 is a three-stage device with 28 dB gain at
full power. Therefore, the drive required to fully saturate the output is +5dBm. Based upon HBT (Heterojunction Bipolar Transistor) technology, the part
requires only a single positive 3V supply to operate to
full specification. Power control is provided through a
single pin interface, with a separate Power Down control pin. The final stage ground is achieved through the
large pad in the middle of the backside of the package.
First and second stage grounds are brought out
through separate ground pins for isolation from the output. These grounds should be connected directly with
vias to the PCB ground plane, and not connected with
the output ground to form a so called “local ground
plane” on the top layer of the PCB. The output is
brought out through the wide output pad, and forms the
RF output signal path.
The amplifier operates in near Class C bias mode. The
final stage is "deep AB", meaning the quiescent current
is very low. As the RF drive is increased, the final stage
self-biases, causing the bias point to shift up and, at
full power, draws about 1500mA. The optimum load for
the output stage is approximately 4.5Ω. This is the load
at the output collector, and is created by the series
inductance formed by the output bond wires, vias, and
microstrip, and 2 shunt capacitors external to the part.
The optimum load impedance at the RF Output pad is
4.5-j3.9Ω. With this match, a 50Ω terminal impedance
is achieved. The input is internally matched to 50Ω
with just a blocking capacitor needed. This data sheet
defines the configuration for GSM operation.
The input is DC coupled; thus, a blocking cap must be
inserted in series. Also, the first stage bias may be
adjusted by a resistive divider with high value resistors
on this pin to VPC and ground. For nominal operation,
however, no external adjustment is necessary as internal resistors set the bias point optimally.
When the device is driven at maximum input power self
biasing would occur. This results in less isolation than
one would expect, and the maximum output power
would be about -15dBm. If the drive power to the PA is
turned on before the GSM ramp-up, higher isolation is
required. In order to meet the GSM system specs
under those conditions, a PIN diode attenuator connected to the input can be turned on. The figure below
shows how the attenuator and its controls are connected.
2-236
VCC
RF IN
750 Ω
500 Ω
5 kΩ
APC
PIN
From Bias
Stages
2 kΩ
AT_EN
The current through the PIN diode is controlled by two
signals: AT_EN and APC. The AT_EN signal allows
current through the PIN diode and is an on/off function.
The APC signal controls the amount of current through
the PIN diode. Normally, the AT_EN signal will be
derived from the VCO ENABLE signal available in
most GSM handset designs. If maximum isolation is
needed before the ramp-up, the AT_EN signal needs to
be turned on before the RF power is applied to the
device input. The current into this pin is not critical, and
can be reduced to a few hundred micro amps with an
external series resistor. Without the resistor, the pin will
draw about 700µA.
Because of the inverting stage at the APC input, the
current through the PIN diode is inverted from the APC
voltage. Thus, when VAPC is high for maximum output
power, the attenuator is turned off to obtain maximum
drive level for the first RF stage. When VAPC is low for
maximum isolation, the attenuator is be turned on to
reduce the drive level and to avoid self-biasing.
The PIN diode is dimensioned such that a low VAPC the
impedance of the diode is about 50 Ohm. Since the
input impedance of the first RF stage become very
high when the bias is turned off, this topology will maintain a good input impedance over the entire VAPC control range.
Rev A6 010720
VCC1 and VCC2 provide supply voltage to the first and
second stage, as well as provides some frequency
selectivity to tune to the operating band. Essentially,
the bias is fed to this pin through a short microstrip. A
bypass capacitor sets the inductance seen by the part,
so placement of the bypass cap can affect the frequency of the gain peak. This supply should be
bypassed individually with 100pF capacitors before
being combined with VCC for the output stage to prevent feedback and oscillations.
The RF OUT pin provides the output power. Bias for
the final stage is fed to this output line, and the feed
must be capable of supporting the approximately 1.5A
of current required. Care should be taken to keep the
losses low in the bias feed and output components. A
narrow microstrip line is recommended because DC
losses in a bias choke will degrade efficiency and
power.
While the part is safe under CW operation, maximum
power and reliability will be achieved under pulsed conditions. The data shown in this data sheet is based on
a 12.5% duty cycle and a 600µs pulse, unless specified otherwise.
RF2174
The HBT breakdown voltage is >20V, so there is no
issue with overvoltage. However, under worst-case
conditions, with the RF drive at full power during transmit, and the output VSWR extremely high, a low load
impedance at the collector of the output transistors can
cause currents much higher than normal. Due to the
bipolar nature of the devices, there is no limitation on
the amount of current the device will sink, and the safe
current densities could be exceeded.
High current conditions are potentially dangerous to
any RF device. High currents lead to high channel temperatures and may force early failures. The RF2174
includes temperature compensation circuits in the bias
network to stabilize the RF transistors, thus limiting the
current through the amplifier and protecting the
devices from damage. The same mechanism works to
compensate the currents due to ambient temperature
variations.
To avoid excessively high currents it is important to
control the VAPC when operating at supply voltages
higher than 4.0V, such that the maximum output power
is not exceeded.
The part will operate over a 3.0V to 5.0V range. Under
nominal conditions, the power at 3.5V will be greater
than +32dBm at +85°C. As the voltage is increased,
however, the output power will increase. Thus, in a system design, the ALC (Automatic Level Control) Loop
will back down the power to the desired level. This
must occur during operation, or the device may be
damaged from too much power dissipation. At 5.0V,
over +36dBm may be produced; however, this level of
power is not recommended, and can cause damage to
the device.
Rev A6 010720
2-237
2
POWER AMPLIFIERS
Preliminary
RF2174
Preliminary
Application Schematic
VCC
12 pF
POWER AMPLIFIERS
2
Very close
to
pin 15/16
1 nF
Instead of a stripline,
an inductor of ~6 nH
can be used
15 pF
1.0 pF
1
16
15
14
13
AT_EN
2
12
RF IN
3
11
VCC
Instead of a stripline, an
inductor of 2.2 nH can
be used
Quarter wave
length
33 pF
50 Ω µstrip
33 pF
4
Distance between
edge of device and
capacitor is 0.240" to
improve the "off"
isolation
5
10
6
7
VCC
15 pF
15 pF
15 pF
3.6 pF
1.3 pF
Note 1
1.3 pF
Note 1
9
VCC
APC
2-238
8
RF OUT
4.3 pF
Distance between
edge of device and
capacitor is 0.080"
Distance center to
center of capacitors
0.220"
15 pF
Note: All capacitors are standard 0402 multi layer chip
Note 1: Using a hi-Q capacitor will increase efficiency slightly
Rev A6 010720
RF2174
Preliminary
Internal Schematic
VCC1
VCC2
RF OUT
2
VCC
APC2
VCC
POWER AMPLIFIERS
APC1
RF IN
750 Ω
500 Ω
500 Ω
200 Ω
VCC
320 Ω
5k Ω
APC1
3k Ω
AT_EN
2.5k Ω
2.5k Ω
1.5k Ω
1.5k Ω
GND1
Rev A6 010720
PKG BASE
PKG BASE
2-239
RF2174
Preliminary
Evaluation Board Schematic
(Download Bill of Materials from www.rfmd.com.)
VEN
VCC
P1
+
POWER AMPLIFIERS
C7
3.3 uF
+
C6
1 nF
C10
1 pF
C5
12 pF
1
C21
1 nF
16
15
14
C1
33 pF
2
12
3
11
+
C12
1 nF
GND
P1-3
3
VCC
P1-4
4
VCC
5
GND
CON5
C9
33 pF
Quarter Wave
Length
C2
33 pF
50 Ω µstrip
4
10
VCC
C20
3.3 uF
C8
1 nF
13
50 Ω µstrip
J1
RF IN
VEN
2
C19
3.3 uF
C22
1 nF
2
1
P1-1
5
C11
27 pF
6
7
8
9
C3
3.6 pF
C26
4.3 pF
C4
1.3 pF
J2
RF OUT
C27
1.5 pF
2174400-
C23
10 nF
C16
1 nF
C13
33 pF
C14
33 pF
VCC
C17
1 nF
C15
33 pF
C25
10 nF
C18
3.3 uF
+
C24
10 nF
50 Ω µstrip
J3
VAPC
2-240
Rev A6 010720
RF2174
Preliminary
Evaluation Board Layout
Board Size 2.0” x 2.0”
Board Thickness 0.032”; Board Material FR-4; Multi-Layer
POWER AMPLIFIERS
2
Rev A6 010720
2-241
RF2174
Preliminary
Typical Test Setup
Power Supply
V- S- S+ V+
POWER AMPLIFIERS
2
RF Generator
Spectrum
Analyzer
3dB
10dB/5W
Buffer
x1 OpAmp
Pulse
Generator
A buffer amplifier is recommended because the current into
the VAPC changes with voltage. As an alternative, the
voltage may be monitored with an oscilloscope.
Notes about testing the RF2174
The test setup shown above includes two attenuators. The 3dB pad at the input is to minimize the effects that the
switching of the input impedance of the PA has on the signal generator. When VAPC is switched quickly, the resulting
input impedance change can cause the signal generator to vary its output signal, either in output level or in frequency.
Instead of an attenuator an isolator may also be used. The attenuator at the output is to prevent damage to the spectrum analyzer, and should be able to handle the power.
It is important not to exceed the rated supply current and output power. When testing the device at higher than nominal
supply voltage, the VAPC should be adjusted to avoid the output power exceeding +36dBm. During load-pull testing at
the output it is important to monitor the forward power through a directional coupler. The forward power should not
exceed +36dBm, and VAPC needs to be adjusted accordingly. This simulates the behavior for the power control loop in
this respect. To avoid damage, it is recommended to set the power supply to limiting the current during the burst, not to
exceed the maximum current rating.
2-242
Rev A6 010720