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RF2504
0
Typical Applications * 2-Way Paging * ISM Band Systems * Wireless Local Loop Systems Product Description
The RF2504 is an integrated oscillator and buffer amplifier chain designed to achieve extremely low sensitivity to fluctuations in load impedance and power supply noise, thereby greatly reducing load pulling and pushing. The IC offers great flexibility, yet is easy to use. This product was designed for use in applications with low supply voltages. It has a power-down feature and is designed to operate from 700MHz to 1500MHz with the help of an external resonator. Frequency control is achieved with an external varactor diode. The IC's ease of use, reduced load pulling, small size, and low cost make it an ideal LO (Local Oscillator) for almost any wireless application.
VCO/HIGH-ISOLATION BUFFER AMPLIFIER
* GPS Receivers * Cellular Systems * Low Voltage Applications
IG N S
0.050 0.157 0.150 0.244 0.229 0.034 0.016 0.009 0.007
-A0.008 0.004
0.018 0.014
0.196 0.189
E S
0.068 0.053
D
W
8 MAX 0 MIN
NOTES: 1. Shaded lead is Pin 1. 2. All dimensions are excluding mold flash. 3. Lead coplanarity 0.005 with respect to datum "A".
Optimum Technology Matching(R) Applied
N E
GaAs MESFET Si CMOS SiGe Bi-CMOS
8 PD 7 GND2 6 RF OUT 5 VCC2
!
Package Style: SOIC-8
Si BJT Si Bi-CMOS InGaP/HBT
GaAs HBT SiGe HBT GaN HEMT
Features * High-Isolation/Reduced Load Pulling * Low Current Consumption * -6dBm Output Power * Digitally Controlled Power Down Mode * 700MHz to 1500MHz Operating Range * Single 2.2V to 5V Supply
N O T
VCC1 1 RES 2 GND1 3 NC 4
FO
R
Ordering Information
RF2504 RF2504 PCBA VCO/High-Isolation Buffer Amplifier Fully Assembled Evaluation Board
Functional Block Diagram
RF Micro Devices, Inc. 7628 Thorndike Road Greensboro, NC 27409, USA
NOT FOR NEW DESIGNS
Tel (336) 664 1233 Fax (336) 664 0454 http://www.rfmd.com
Rev A4 021007
12-1
RF2504
Absolute Maximum Ratings Parameter
Supply Voltage Power Down Voltage (VPD) Operating Ambient Temperature Storage Temperature
Rating
-0.5 to +5.8 -0.5 to +5.8 -40 to +85 -55 to +150
Unit
VDC VDC C C 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).
Parameter
Overall
Operating Frequency
Specification Min. Typ. Max.
700 to 1500
Unit
MHz
Condition
915MHz Operation
Output Power 2nd Harmonic 3rd Harmonic Load Pulling VCC Pushing Phase Noise -6 -8 -19 200 4.7 -104 -83
Operating Voltage Supply Current
2.2 to 5.0 5.5
D
Power Supply
N O T
12-2
FO
R
N E
W
E S
dBc VDC mA
dBm dBc dBc kHz MHz/V dBc
IG N S
Into 1.67VSWR Load
T=25 C, VCC =2.7V, ZLOAD =50, VPD =2.7V
100kHz Offset. Better phase noise is achievable at the expense of output power. 10kHz Offset At 2.2V and -40C, output power will be reduced to typically -11dBm.
Rev A4 021007
RF2504
Pin 1 Function VCC1 Description Interface Schematic
Power supply connection for the VCO. This pin should be well bypassed close to the package with a capacitor suitable for the frequency of operation as well as a capacitor to minimize low frequency noise from the voltage supply. The ground side of the capacitors should connect immediately to ground plane. Connection point for the resonator circuit. The resonator is an inductive To Bias Ckts. element. Changing the effective inductance, either physically or with a varactor tuned circuit, will change the frequency of operation. Note that all parasitics on the circuit board will contribute to the effective inducPin 2 tance and will influence the frequency of operation. These effects become more pronounced at higher operating frequencies. This pin has DC bias present. A DC blocking capacitor, suitable for the frequency of operation, should be used if the external circuitry has DC present or presents a DC path to ground. See Application Example Pins Schematic and Theory of Operation section of this data sheet for 3,4 design details. Ground connection for the VCO. Keep traces physically short and con- See Pin 2 nect immediately to ground plane for best performance. In order to minimize load pulling, it is recommended that pin 3 have a different return path to ground than pin 7 (i.e., separate vias to a common ground plane). Not connected. Power supply connection for the buffer amplifiers. This pin should be well bypassed close to the package with a capacitor suitable for the frequency of operation. The ground side of the capacitor should connect immediately to ground plane. RF output pin. This is an open-collector output and must be biased externally. A shunt bias/matching inductor to VCC and a series blocking/matching capacitor are recommended. See Application Example Schematic. Ground connection for the buffer amplifiers. Keep traces physically short and connect immediately to ground plane for best performance. In order to minimize load pulling, it is recommended that pin 3 have a different return path to ground than pin 7 (i.e., separate vias to a common ground plane). Power Down pin for the VCO and buffer amplifiers. A logic "low" (0.0 to 0.7V) turns the entire device off and supply current drops to less than 1A. A logic "high" (3.0V) turns the device on. Note that the voltage on this pin should never exceed 5.5VDC.
2
RES
To Buffer Amps and Bias Ckts.
3
GND1
4 5
NC VCC2
6
RF OUT
7
GND3
8
PD
N O T
Rev A4 021007
FO
R
N E
W
D
E S
IG N S
12-3
RF2504
Application Notes
The RF2504 has two functional parts: an oscillator and buffer amplifier. The functional blocks have separate ground and VCC pins to increase the isolation and reduce load pulling, one of the key design objectives. An external resonator is used to add design flexibility, and the loaded Q of this resonator will affect the performance of the resulting oscillator. To create an oscillation, negative resistance is generated at pin 2 with a circuit similar to a Colpitts oscillator. The input impedance at pin 2, measured with a vector network analyzer, is shown here in the data sheet. In general, the impedance looks like a negative resistance in series with a capacitor. The negative resistance decays as the frequency increases. An oscillator is created when an inductive element is placed on pin 2 that is the conjugate of the capacitive reactance. A greater inductive element will create a lower frequency of oscillation. The S11 looking into pin 2 is also shown here in the data sheet. It has return gain from 500 MHz to 2200 MHz at room temperature. The specified frequency range of 750 MHz to 1500 MHz defines the region where the output power is relatively flat. At lower and higher frequencies, the power will tend to roll off from the nominal value. The specified frequency range is conservatively set to ensure oscillation and maintain performance, but the RF2504 can be used over a broader frequency range with degraded performance. The overall Q of the external resonator will affect performance. Lower Q means lower power, higher phase noise, and more load pulling. If the Q is too low, the circuit will not oscillate. The IC is designed to oscillate into a resonator with Q>10. The performance is measured with a microstrip resonator or high quality inductor, which usually has a Q>50. These measurements define the best performance that can be expected from the ICs. Lower Q resonators, particularly those including a lossy varactor, might have degraded performance. The specified output power is measured into a 50 load. The IC has a high output impedance, and if desired, output matching can be used to obtain more power by transforming 50 into a higher impedance. On the RF2504, this could be accomplished by simply changing the values of the external output inductor and capacitor.
N O T
12-4
FO
R
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W
D
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IG N S
Rev A4 021007
RF2504
Application Schematic 915 MHz Operation
VCC
1 F
100 pF 1 12 nH 100 pF 2 3 8 7
V 100 pF PD
47 k VTUNE 100 pF
100 pF 6 5 RF OUT 27 nH VCC 100 pF SMV1235-011 4
N O T
Rev A4 021007
FO
R
N E
W
D
E S
IG N S
12-5
RF2504
Evaluation Board Schematic 915MHz Operation
(Download Bill of Materials from www.rfmd.com.)
P1 P1-1 1 2 P1-3 3 PD GND VCC NC P2-1 P2 1 2 3 VTUNE GND
2504400VCC C9 10 F C3 100 pF 1 2 D1* L2 12 nH C4 100 pF 3 4 *Alpha SMV1235-011
IG N S
8 7 6 5 C1 100 pF C8 10 F C5 100 pF L1 27 nH C2 100 pF C7 10 F
PD
R1 47 k VTUNE C6 100 pF
RF OUT J1
E S D
VCC
N O T
12-6
FO
R
N E
W
Rev A4 021007
RF2504
Evaluation Board Layout 915MHz Operation Board Size 2.0" x 2.0"
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Rev A4 021007
FO
R
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W
D
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IG N S
12-7
RF2504
50.0 40.0 30.0 20.0 10.0 0.0 -10.0 -20.0 -30.0 -40.0 -50.0 0.0 500.0 1000.0 1500.0 2000.0 2500.0 R Reference A R Reference B X Reference A X Reference B
Input Impedance VCC = 5.0 V
50.0 0.0 -50.0
3.0 Reference A 2.5 Reference B
S11 VCC = 2.7 V
2.0 -100.0 -150.0 1.5
R (Ohms)
S11 (dB)
-200.0 -250.0 -300.0
1.0
0.5
0.0 -350.0 -400.0 -450.0 3000.0 -0.5
-1.0 0.0
IG N S
500.0 1000.0 1500.0 2000.0
2500.0
3000.0
Frequency (MHz)
Frequency (MHz)
960.0 Frequency 950.0 Power
0.0 -1.0 -2.0
E S
50.0 40.0 30.0 20.0 10.0 0.0 -10.0 -20.0 -30.0 -40.0 -50.0 0.0 500.0
Evaluation Board Data
Input Impedance VCC = 2.7 V
50.0 0.0 -50.0 R Reference A R Reference B X Reference B X Reference A -100.0 -150.0 -200.0 -250.0 -300.0 -350.0 -400.0 -450.0
940.0 -3.0
Frequency (MHz)
W
R (Ohms)
920.0
-5.0 -6.0 -7.0 -8.0 -9.0
910.0
900.0
890.0
880.0 0.0 0.5 1.0
R
1.5
N E
-10.0 2.5 3.0
2.0
1000.0
1500.0
2000.0
2500.0
3000.0
FO
VTune (V)
Frequency (MHz)
N O T
0603 100 pF Pin 2
A B Reference positions for input impedance measurements of RF2504
12-8
Rev A4 021007
X (Ohms)
-4.0
Power (dBm)
930.0
D

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