DEMO MANUAL DC2078A
LTC6430-20
50MHz TO 1000MHz
75Ω INPUT/OUTPUT CATV AMPLIFIER
DESCRIPTION
Demonstration circuit 2078A is a 75Ω input and 75Ω output
push-pull CATV amplifier featuring the LTC®6430‑20. The
LTC6430-20 has a power gain of 20.8dB and is part of the
LTC6430-YY amplifier series.
The DC2078A demo board is optimized for the frequency
range from 50MHz to 1000MHz. It incorporates a minimum of passive support components to configure the
amplifier for the CATV applications with 75Ω input and
output impedance.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2078A
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
LTC6430-20 BLOCK DIAGRAM
VCC
9, 22
BIAS AND TEMPERATURE
COMPENSATION
24
+IN
20dB
GAIN
+OUT
T_DIODE
7
–IN
20dB
GAIN
–OUT
18
16
13
GND
8, 14, 17, 23 AND PADDLE 25
643020 BD
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DEMO MANUAL DC2078A
PERFORMANCE SUMMARY
TA = 25°C, VCC = 5V
Table 1. Typical Demo Board Performance Summary
SYMBOL
PARAMETER
CONDITIONS
VALUE/UNIT
VCC
Operating Supply Range
All VCC Pins Plus ±OUT
4.75V to 5.25V
ICC
Current Consumption
Total Current
170mA
Power Supply
FREQUENCY
(MHz)
POWER GAIN
|S21|
OUTPUT THIRDORDER INTERCEPT
POINT1
OIP3
OUTPUT THIRDORDER INTERMODULATION1
OIM3
SECOND
HARMONIC
DISTORTION2
HD2
THIRD
HARMONIC
DISTORTION2
HD3
OUTPUT 1DB
COMPRESSION
POINT
P1DB
NOISE
FIGURE3
NF
50
19.1
46.5
-91.0
-86.4
-87.6
22.3
3.5
100
19.1
46.7
-91.4
-86.6
-82.7
22.6
3.5
200
19.1
45.6
-89.3
-82.2
-79.0
22.8
3.5
240
19.1
44.5
-86.9
-80.8
-78.2
22.9
3.4
300
19.1
43.7
-85.4
-73.4
-72.9
23.4
3.4
400
19.3
44.1
-86.2
-66.6
-73.2
24.0
3.4
500
19.4
46.8
-91.6
-62.6
24.2
3.5
600
19.2
47.0
- 92.0
24.3
3.8
700
18.8
46.3
-90.6
23.7
4.3
800
18.5
43.7
-85.4
22.8
4.7
900
18.4
41.9
-81.9
22.5
5.0
1000
18.5
41.5
-81.0
22.7
5.0
Units
dB
dBm
dBc
dBm
dB
dBc
dBc
Notes: All figures are referenced to J1 (Input Port) and J4 (Output Port).
1. Two-tone test conditions: Output power level = +1dBm/tone, tone spacing = 1MHz.
2. Single-tone test conditions: Output power level = +6dBm.
3. Small-signal noise figure.
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DEMO MANUAL DC2078A
OPERATION
Demo circuit 2078A is a high linearity, fixed gain amplifier.
To configure the demo circuit 2078A for use in the 75Ω
CATV environment, a transformer with 1:1.33 impedance
ratio is added at the board’s input and output. These
transformers transform the differential 100Ω impedance
of the LTC6430-20 to single-ended 75Ω impedance. The
frequency range of the circuits is limited by the balun
transformers. Hence, the demo board has a nominal working frequency range from 50MHz to 1000MHz. Figure 2
shows the S-parameters of demo board.
Demo circuit 2078A is shipped with 75Ω F-type connectors (J1 and J2) at both input and output. Depending on
the user’s preference, the board may also accept other
connector types such as BNC or SMA. Please note that
the use of substandard connectors can limit the usable
bandwidth of the circuit.
The input and output transformers (T3 and T4) convert the
differential signal to single-ended 75Ω signal for compatibility with the CATV environment, while preserving all the
exceptional characteristics of the LTC6430-20. In addition,
the balun’s excellent phase balance and the second order
linearity of the LTC6430-20 combine to further suppress
second order products across the entire CATV band.
Figure 3 shows the spurious products (in dBc) within the
passband frequency 50MHz to 1000MHz. The output thirdorder intermodulation (OIM3) and the second harmonic
distortion (HD2) are shown as a function of frequency.
Frequency appropriate chokes (L1 and L2) and the decoupling capacitors (C9, C10, C11 and C12) provide bias to
the RF ±OUT nodes. Only a single 5V supply is necessary
for the VCC pins on the device.
Table 2. DC2078A Board I/O Descriptions
CONNECTOR
J1 (IN)
|S21|
20
E1 (VCC)
E2 (GND)
E3 (T_DIODE)
In this particular application circuit, the input stability
networks (C3, C4, R1, R2) are not required since the
LTC6430-20 is preceded by a low frequency termination
from the balun transformer. In a wideband differential
application where the bandwidth extends below 20MHz,
the input stability network is suggested.
0
–4
–16
14
12
–20
|S11|
10
8
–24
–28
|S12|
–20
OIM3, HD2 (dBc)
–12
|S11|, |S12|, |S22| (dB)
|S22|
16
–30
–40
–50
–60
–70
6
–32
4
–36
–80
2
–40
–90
–44
1240
–100
0
40
240
440
640
840
FREQUENCY (MHz)
1040
DC2078a F02
OIM3, POUT = 1dBm/TONE
HD2, POUT = 6dBm
–10
–8
18
FUNCTION
Single-Ended Input. Impedance
Matched to 75Ω.
Single-Ended Output. Impedance
Matched to 75Ω.
Positive Supply Voltage Source.
Negative Supply Ground.
The measured voltage will be an indicator of the chip junction temperature.
J2 (OUT)
0
22
|S21| (dB)
The input and output DC blocking capacitors (C1, C2,
C7 and C8) are required because this device is internally
biased for optimal operation.
HD2
OIM3
0
200
600
400
FREQUENCY (MHz)
800
1000
DC2078a F03
Figure 2. Demo Board S-Parameters
Figure 3. OIM3 and HD2 vs Frequency
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DEMO MANUAL DC2078A
OPERATION
L3, L4, C19 and C20 are optional parts. They are for additional matching components when further optimization to
a lower or wider frequency range applications is required.
Table 2 shows the function of each input and output on
the board.
Additional Information
As with any RF device, minimizing ground inductance is
critical. Care should be taken with the board layout because
of the exposed pad packages. The maximum number of
minimum diameter vias holes should be placed underneath
the exposed pad. This will ensure good RF ground and low
thermal impedance. Maximizing the copper ground plane
will also improve heat spreading and lower the inductance
to ground. It is a good idea to cover the via holes with
solder mask on the back side of the PCB to prevent solder
from wicking away from the critical PCB to the exposed
pad interface.
Please note that a number of DNC pins are connected on
the demo board. These connections are not necessary for
normal operation, however, failure to float these pins may
impair the operation of the device.
Table 3 shows the LTC643X-YY amplifier series and its
associated demo boards. Each demo board lists the typical
working frequency range and the input and output impedance of the amplifiers.
Setup Signal Sources and Spectrum Analyzer
The LTC6430-20 is an amplifier with high linearity performance. Therefore, the output intermodulation products are
very low. Even using high dynamic range test equipment,
Third-Order Intercept (IP3) measurements can drive test
setups to their limits. Consequently, accurate measurement of IP3 for a low distortion IC such as the LTC6430-20
requires certain precautions to be observed in the test
setup as well as in the testing procedure.
The T_DIODE Pin (Turret E3) can be forward biased to
ground with 1mA of current. The measured voltage will
be an indicator of the chip junction temperature (TJ).
Table 3. The LTC643X-YY Amplifier Family and Corresponding Application Demo Boards
FREQUENCY RANGE
(MHz)
NOTES/APPLICATIONS
BOARD’S IN/OUT
IMPEDANCE
AMPLIFIER
AMPLIFIER’S
IMPEDANCE
DC1774A-A
50 to 350
Low Frequency
50Ω
LTC6430-15
Differential 100Ω
DC1774A-B
400 to 1000
Mid Frequency
50Ω
LTC6430-15
Differential 100Ω
DC1774A-C
100 to 1200
Wide Frequency
50Ω
LTC6431-15
Single-ended 50Ω
DC2032A
50 to 1000
Cable Infrastructure
75Ω
LTC6430-15
Differential 100Ω
DC2077A
100 to 1200
Wide Frequency
50Ω
LTC6431-20
Single-ended 50Ω
DC2153A
700 to 1700
High Frequency
50Ω
LTC6430-15
Differential 100Ω
DEMO BOARD NUMBER
DC2090A
50 to 1200
Power Doubler
50Ω
Dual LTC6430-15
Differential 50Ω
DC2076A-A
50 to 350
Low Frequency
50Ω
LTC6430-20
Differential 100Ω
DC2076A-B
350 to 1000
Mid Frequency
50Ω
LTC6430-20
Differential 100Ω
DC2078A
50 to 1000
Cable Infrastructure
75Ω
LTC6430-20
Differential 100Ω
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DEMO MANUAL DC2078A
OPERATION
Setup Signal Sources
Setup the Spectrum Analyzer
Figure 4 shows a proposed IP3 test setup. This setup has
low phase noise, good reverse isolation, high dynamic
range, sufficient harmonic filtering and wideband impedance matching. The setup is outlined below:
a. Adjust the spectrum analyzer for maximum possible
resolution of the intermodulation products’ amplitude
in dBc. A narrower resolution bandwidth will take a
longer time to sweep.
a. High performance signal generators 1 and 2 (HP8644A)
are used. These suggested generators have low harmonic distortion and very low phase noise.
b. Optimize the dynamic range of the spectrum analyzer
by adjusting the input attenuation. First increase the
spectrum analyzer’s input attenuation (normally in
steps of 5dB or 10dB). If the IM product levels decrease
when the input attenuation is increased, then the input
power level is too high for the spectrum analyzer to
make a valid measurement. Most likely, the spectrum
analyzer’s 1st mixer was overloaded and producing its
own IM products. If the IM reading holds constant with
increased input attenuation, then a sufficient amount
of attenuation was present. Adding too much attenuation will bury the intended IM signal in the noise floor.
Therefore, select just enough attenuation to achieve a
stable and valid measurement.
b. High linearity amplifiers are used to improve the reverse
isolation. This prevents cross talk between the two
signal generators and provides higher output power.
c. A low pass filter is used to suppress the harmonic content
from interfering with the test signal. Note that second
order inputs can “mix” with the fundamental frequency
to form intermodulation (IM) products of their own. We
suggest filtering the harmonics to –50dBc or better.
d. The signal combiner from Mini-Circuits (ADP-2-9)
combines the two isolated input signals. This combiner
has a typical isolation of 27dB. For improved VSWR and
isolation, the H-9 signal combiner from MA/COM is an
alternative which features >40dB isolation and a wider
frequency range. Passive devices (e.g. combiners) with
magnetic elements can contribute nonlinearity to the
signal chain and should be used cautiously.
e. The attenuator pads on all three ports of the signal
combiner will further support isolation of the two input
signal sources. They also reduce reflections and promote
maximum power transfer with wideband impedance
matching.
c. In order to achieve this valid measurement result, the
test system must have lower total distortion than the
DUT’s intermodulation. For example, to measure a
47dBm OIP3, the measured intermodulation products
will be –92dBc below an –18dBm/tone input level and
the test system must have intermodulation products
approximately –98dBc or better. For best results,
the IM products and noise floor should measure at
least –102dBc before connecting the DUT.
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DEMO MANUAL DC2078A
QUICK START PROCEDURE
Demo circuit 2078A can be set up to evaluate the performance of the LTC6430-20. Refer to Figure 4 for proper
equipment connections and follow the procedure below:
Two-Tone Measurement:
Connect all test equipment as suggested in Figure 4.
1. The power labels of “VCC 4.75V-5.25V” and GND directly correspond to the power supply. Typical current
consumption of the LTC6430-20 is about 170mA.
2. Apply two independent signals f1 and f2 from signal
generator 1 and signal generator 2 at 600MHz and
601MHz, while setting the amplitude to –18dBm/tone
at the demo board input (J1).
3. Monitor the output tone level on the spectrum analyzer.
Adjust the signal generator levels such that the output
power measures +1dBm/tone at the amplifier output
J2, after correcting for external cable losses, minimum
loss matching pads and attenuations.
4. Change the spectrum analyzer’s center frequency and
observe the two IM3 tones at 1MHz below and above
the input frequencies. The frequencies of IM3_LOW and
IM3_HIGH are 599MHz and 602MHz, respectively. The
measurement levels should be approximately –92dBc;
+47dBm is typical OIP3 performance for the LTC6430‑20
at 600MHz.
The OIP3 calculation is:
OIP3 = POUT + ∆IMD3/2
Where:
POUT is the lower output signal power of the fundamental products.
∆IMD3 = POUT – PIM3; PIM3 is the higher Third-Order
intermodulation product.
Single-tone Measurement
5. Continue with step 4 above, turn off one signal source
to measure gain and harmonic distortions.
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DEMO MANUAL DC2078A
QUICK START PROCEDURE
SIGNAL
GENERATOR 1
(HP8644A)
AMPLIFIER
MINI-CIRCUITS, ZHL-2
OR EQUIVALENT
20dB ATTENUATION PAD
(MATCHES DUT GAIN)
LOW PASS FILTER
DUT GAIN
APPROX. 19dB
3dB ATTENUATION PAD
6dB ATTENUATION PAD
(OPTIONAL)
1dBm/TONE
COAXIAL CABLE
–5.7dB
–5.7dB
COMBINER
MINI-CIRCUITS
ADP-2-9 OR
EQUIVALENT
50Ω
6dB ATTENUATION PAD
(OPTIONAL)
LOW PASS FILTER
AMPLIFIER
MINI-CIRCUITS, ZHL-2
OR EQUIVALENT
SIGNAL
GENERATOR 2
MINIMUM LOSS
MATCHING PAD
MINIMUM LOSS
MATCHING PAD
75Ω
75Ω
MINI-CIRCUITS
BMP-5075R
OR
EQUIVALENT
MINI-CIRCUITS
BMP-5075R
OR
EQUIVALENT
APPROX.
–12dBm/TONE
50Ω
APPROX.
–18dBm/TONE
DC POWER
SUPPLY
GND
SPECTRUM
ANALYZER
ROHDE AND
SCHWARZ
FSEM30
DC2078a F04
VCC = 4.75V TO 5.25V
V+
(HP8644A)
Figure 4. Proper Equipment Setup for IP3 Measurement
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DEMO MANUAL DC2078A
PARTS LIST
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART #
1
4
C1, C2, C7,C8
CAP., X5R, 0.047μF, 25V 10%, 0603
AVX, 06033D473KAT2A
2
0
C3, C4, C19, C20
3
2
C5, C6
CAP., X7R, 1000pF, 50V 5%, 0402
AVX, 04025C102JAT2A
4
2
C9, C11
CAP., X5R, 0.1μF, 10V, 10%, 0603
AVX, 0603ZD104KAT2A
5
2
C10, C12
CAP., X7R, 1000pF, 50V 5%, 0603
AVX, 06035C102JAT2A
6
3
E1, E2, E3
TESTPOINT, TURRET, 0.095"
MILL-MAX, 2501-2-00-80-00-00-07-0
7
2
J1, J2
F TYPE END LAUNCH JACK FOR 0.062” PCB, 75Ω
AMPHENOL CONNEX, 222181
8
2
L1, L2
INDUCTOR, CHIP, 560nH, 5%, 0603LS-1608
COILCRAFT, 0603LS-561XJLB
9
2
L3,L4
RES., CHIP, 0Ω, 0603
VISHAY, CRCW06030000Z0ED
10
2
R1,R2
RES., CHIP, 0Ω, 0603
VISHAY, CRCW06030000Z0ED
11
1
R3
12
2
T3, T4
RF TRANSFORMER TC1.33-282+, CASE STYLE: AT224-1
MINI-CIRCUITS, TC1.33-282+
13
1
U1
BALANCED AMPLIFIER LTC6430AIUF-20, QFN24UF-4X4
LINEAR TECH., LTC6430AIUF-20
CAP., 0603, OPT
R-0402, OPT
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Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
A
B
C
D
5
4
4
3
3
5
2
1
1
CATV AMPLIFIER
TECHNOLOGY
2
A
B
C
D
DEMO MANUAL DC2078A
SCHEMATIC DIAGRAM
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DEMO MANUAL DC2078A
DEMONSTRATION BOARD IMPORTANT NOTICE
Linear Technology Corporation (LTC) provides the enclosed product(s) under the following AS IS conditions:
This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT
OR EVALUATION PURPOSES ONLY and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete
in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety
measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union
directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations.
If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date
of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU
OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS
FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR
ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.
The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user releases LTC from all claims
arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all
appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or
agency certified (FCC, UL, CE, etc.).
No License is granted under any patent right or other intellectual property whatsoever. LTC assumes no liability for applications assistance,
customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.
LTC currently services a variety of customers for products around the world, and therefore this transaction is not exclusive.
Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and
observe good laboratory practice standards. Common sense is encouraged.
This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LTC application
engineer.
Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation
dc2078af
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