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DEMO MANUAL DC2078A
DESCRIPTION
LTC6430-20
50MHz TO 1000MHz
75Ω INPUT/OUTPUT CATV AMPLIFIER
Demonstration circuit 2078A is a 75Ω input and 75Ω output
push-pull CATV amplifier featuring the LT C
®
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 mini-
mum of passive support components to configure the
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
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
643020 BD
VCC
9, 22
+IN
BIAS AND TEMPERATURE
COMPENSATION
20dB
GAIN
20dB
GAIN
GND
8, 14, 17, 23 AND PADDLE 25
24
–IN
+OUT
T_DIODE
–OUT
7
18
16
13
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DEMO MANUAL DC2078A
FREQUENCY
(MHz)
POWER GAIN
|S21|
OUTPUT THIRD-
ORDER INTERCEPT
POINT1
OIP3
OUTPUT THIRD-
ORDER INTER-
MODULATION1
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 dBc dBc dBm dB
Notes: All figures are referenced to J1 (Input Port) and J4 (Output Port).
1. Tw o -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.
PERFORMANCE SUMMARY
TA = 25°C, VCC = 5V
Table 1. Typical Demo Board Performance Summary
SYMBOL PARAMETER CONDITIONS VALUE/UNIT
Power Supply
VCC Operating Supply Range All VCC Pins Plus ±OUT 4.75V to 5.25V
ICC Current Consumption Total Current 170mA
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DEMO MANUAL DC2078A
OPERATION
The input and output DC blocking capacitors (C1, C2,
C7 and C8) are required because this device is internally
biased for optimal operation.
Frequency appropriate chokes (L1 and L2) and the decou-
pling 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.
Figure 2. Demo Board S-Parameters Figure 3. OIM3 and HD2 vs Frequency
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 work-
ing frequency range from 50MHz to 1000MHz. Figure 2
shows the S-parameters of demo board.
Demo circuit 2078A is shipped with 75Ω F-type connec-
tors (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 compat-
ibility 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 third-
order intermodulation (OIM3) and the second harmonic
distortion (HD2) are shown as a function of frequency.
Table 2. DC2078A Board I/O Descriptions
CONNECTOR FUNCTION
J1 (IN) Single-Ended Input. Impedance
Matched to 75Ω.
J2 (OUT) Single-Ended Output. Impedance
Matched to 75Ω.
E1 (VCC) Positive Supply Voltage Source.
E2 (GND) Negative Supply Ground.
E3 (T_DIODE) The measured voltage will be an indica-
tor of the chip junction temperature.
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.
FREQUENCY (MHz)
40
|S21| (dB)
22
20
16
12
8
4
18
14
10
6
2
0240
DC2078a F02
1240640 840440 1040
|S11|, |S12|, |S22| (dB)
–44
–24
–20
–16
–8
–28
–32
–36
–40
–4
0
–12
|S22|
|S11|
|S12|
|S21|
FREQUENCY (MHz)
0
OIM3, HD2 (dBc)
–100
–70
–60
–40
–50
–20
600 800
DC2078a F03
–80
–90
–10
0
–30
200 400 1000
OIM3, POUT = 1dBm/TONE
HD2, POUT = 6dBm
OIM3
HD2
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DEMO MANUAL DC2078A
L3, L4, C19 and C20 are optional parts. They are for ad-
ditional 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.
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
DEMO BOARD NUMBER
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
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
OPERATION
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 imped-
ance of the amplifiers.
Setup Signal Sources and Spectrum Analyzer
The LTC6430-20 is an amplifier with high linearity perfor-
mance. 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 measure-
ment 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.
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DEMO MANUAL DC2078A
Setup Signal Sources
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 imped-
ance matching. The setup is outlined below:
a. High performance signal generators 1 and 2 (HP8644A)
are used. These suggested generators have low har-
monic distortion and very low phase noise.
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 orbetter.
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.
Setup the Spectrum Analyzer
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.
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 attenua-
tion will bury the intended IM signal in the noise floor.
Therefore, select just enough attenuation to achieve a
stable and valid measurement.
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.
OPERATION
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DEMO MANUAL DC2078A
Demo circuit 2078A can be set up to evaluate the perfor-
mance of the LTC6430-20. Refer to Figure 4 for proper
equipment connections and follow the procedure below:
Tw o -Tone Measurement:
Connect all test equipment as suggested in Figure 4.
1. The power labels of “VCC 4.75V-5.25V” and GND di-
rectly 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.
QUICK START PROCEDURE
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 funda-
mental 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
Figure 4. Proper Equipment Setup for IP3 Measurement
QUICK START PROCEDURE
DC2078a F04
MINIMUM LOSS
MATCHING PAD
75Ω 50Ω
MINI-CIRCUITS
BMP-5075R
OR
EQUIVALENT
–5.7dB
VCC = 4.75V TO 5.25V
COAXIAL CABLE
3dB ATTENUATION PAD
(HP8644A)
AMPLIFIER
LOW PASS FILTER
LOW PASS FILTER
MINI-CIRCUITS, ZHL-2
OR EQUIVALENT
AMPLIFIER
MINI-CIRCUITS, ZHL-2
OR EQUIVALENT
6dB ATTENUATION PAD
(OPTIONAL)
ROHDE AND
SCHWARZ
FSEM30
20dB ATTENUATION PAD
(MATCHES DUT GAIN)
MINIMUM LOSS
MATCHING PAD
75Ω50Ω
MINI-CIRCUITS
BMP-5075R
OR
EQUIVALENT
APPROX.
–18dBm/TONE
1dBm/TONE
DUT GAIN
APPROX. 19dB
APPROX.
–12dBm/TONE
SPECTRUM
ANALYZER
–5.7dB
COMBINER
MINI-CIRCUITS
ADP-2-9 OR
EQUIVALENT
SIGNAL
GENERATOR 1
(HP8644A)
SIGNAL
GENERATOR 2
6dB ATTENUATION PAD
(OPTIONAL)
DC POWER
SUPPLY
V+
GND
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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 CAP., 0603, OPT
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 R-0402, OPT
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
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DEMO MANUAL DC2078A
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 representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
SCHEMATIC DIAGRAM
5
5
4
4
3
3
2
2
1
1
D D
C C
B B
A A
TECHNOLOGY
CATV AMPLIFIER
TECHNOLOGY
CATV AMPLIFIER
TECHNOLOGY
CATV AMPLIFIER
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DEMO MANUAL DC2078A
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com
LINEAR TECHNOLOGY CORPORATION 2014
LT 1014 • PRINTED IN USA
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:
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1630 McCarthy Blvd.
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Copyright © 2004, Linear Technology Corporation
