DC1774A-B - Demo Manual

DEMO MANUAL DC1774A-B
LTC6430-15
400MHz to 1000MHz Differential
ADC Driver/IF Amplifier
DESCRIPTION
Demonstration circuit 1774A-B is a differential ADC
driver/IF amplifier featuring the LTC®6430-15. It is part
of the DC1774A demo board family supporting the
LTC643X‑YY amplifier series. The DC1774A-B is optimized for a frequency range of 400MHz to 1000MHz and
utilizes a minimum of passive external components to
configure the amplifier for this application.
to convert the impedance to 50Ω single-ended so that it
can be easily evaluated with commercially available RF
test equipment.
Design files for this circuit board are available at
http://www.linear.com/demo
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.
Because the LTC6430-15 has 100Ω differential input and
output impedance, the demo circuit uses transformers
BLOCK DIAGRAM
GND
8, 14, 17, 23 AND PADDLE 25
VCC
9, 22
BIAS AND TEMPERATURE
COMPENSATION
24
+IN
+OUT
15dB
GAIN
T_DIODE
7
–IN
15dB
GAIN
–OUT
18
16
13
GND
8, 14, 17, 23 AND PADDLE 25
Figure 1. LTC6430-15 Block Diagram
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DEMO MANUAL DC1774A-B
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 Pins
4.75 to 5.25V
ICC
Current Consumption
Total Current
160mA
Power Supply
OUTPUT
OUTPUT
THIRD ORDER
THIRD ORDER
INTERCEPT
INTERMODULATION
POINT (NOTE 1)
(NOTE 1)
OIP3 (dBm)
OIM3 (dBm)
SECOND
HARMONIC
DISTORTION
(NOTE 2)
HD2 (dBc)
THIRD HARMONIC OUTPUT 1dB
DISTORTION
COMPRESSION
(NOTE 2)
POINT
HD3 (dBc)
P1dB (dBm)
NOISE FIGURE
(NOTE 3)
NF (dB)
FREQUENCY
(MHz)
POWER GAIN
|S21| (dB)
400
14.8
46.5
–89.0
–71.2
–81.2
22.9
3.8
500
14.6
46.6
–89.3
–80.3
–76.1
23.0
4.0
600
14.5
46.2
–88.3
–67.4
–73.2
22.7
4.2
700
14.4
45.2
–86.5
–64.7
–68.1 (Note 4)
22.4
4.3
800
14.2
43.0
–82.0
–61.6
–70.6 (Note 4)
22.0
4.7
900
13.9
43.3
–82.6
–65.0
–67.7 (Note 4)
21.7
4.7
1000
13.6
43.1
–82.1
–70.6 (Note 4)
–64.5 (Note 4)
21.5
4.8
All figures are referenced to J7 (input port) and J8 (output port).
Note 1: 2-tone test condition: output power level = 2dBm/tone;
tone spacing = 1MHz.
Note 2: Single-tone test condition: output power level = 8dBm.
Note 3: Small-signal noise figure.
Note 4: Out of input and output transformers working frequency range.
OPERATION
NOMINAL WORKING
FREQUENCY RANGE
18
16
–4
|S21|
|S21| (dB)
14
–8
|S11|
12
|S22|
10
–12
–16
8
–20
|S12|
6
4
200
0
400
1000
800
600
FREQUENCY (MHz)
|S11|, |S12|, |S22| (dB)
The demo circuit 1774A-B is a highly linear fixed-gain
amplifier. The LTC6430-15 is internally matched to a 100Ω
differential source and a load impedance from 20MHz to
1300MHz. Due to the unpopularity of 100Ω differential
test equipment, transformers have been added to convert
impedance from differential 100Ω to single-ended 50Ω
for the input and the output ports. The frequency range
of the circuit is limited by the balun transformers. Hence,
this demo board works best with a frequency range from
400MHz to 1000MHz. Figure 2 shows the performance
of the demo board.
–24
–28
1200
Figure 2. Demo Board DC1774A-B S-Parameters
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2
DEMO MANUAL DC1774A-B
OPERATION
Figure 3 shows the simplified demo circuit schematic. It
requires a minimum of passive supporting components.
The 2:1 transformers convert the differential to singleended 50Ω for compatibility with most test equipment.
The input and output DC blocking capacitors (C1, C2,
C3 and C4) are required because this device is internally
biased for optimal operation. The frequency appropriate
choke (L1 and L2) and the decoupling capacitors (C5, C21,
C22 and C23) provide bias to the RF ±OUT nodes. Only a
single 5V supply is necessary for VCC pins on the device.
An optional stability network has been added. It consists
of parallel 62pF (C8 and C9) and 348Ω (R1 and R2) to
ensure low frequency stability.
Table 2 shows the function of each input and output on
the board.
Table 2. DC1774A-B Board I/O Descriptions
CONNECTOR
FUNCTION
J7 (+IN)
Single-Ended Input. Impedance-Matched to 50Ω.
Drive from a 50Ω Network Analyzer or Signal
Source.
J8 (–OUT)
Single-Ended Output. Impedance-Matched to 50Ω.
Drive from a 50Ω Network Analyzer or Spectrum
Analyzer.
E3 or J11 (VCC)
Positive Supply Voltage Source.
E6 or J18 (GND)
Negative Supply Ground.
Figure 3. Simplified Demo Board DC1774A-B Schematic
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DEMO MANUAL DC1774A-B
ADDITIONAL INFORMATION
The particular element values shown in the demo board
schematic are chosen for wide bandwidth operation.
Depending on the desired frequency, performance may
be improved by the proper selection of these supporting
components.
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 via 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 low inductance. 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 DC1774A-B has a nominal working frequency range
from 400MHz to 1000MHz. It is not intended for operation down to DC. The lower frequency cutoff is limited by
on-chip matching elements.
The generic LTC643X-YY amplifier series demo PCB is
shown in the Schematic Diagram of Figure 6. Hence, the
board can be modified for multiple demo board versions.
For example, both the DC1774A-A and DC1774A-B demo
boards have a differential driver at U1; therefore, the board
is using transformers to transform from differential to
single-ended input and output. Likewise, the DC1774A-C
is a single-ended demo board; consequently, it uses the
LTC6431-15 for single-ended input and output.
Setup Signal Sources
Figure 5 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 here:
1.High performance signal generators 1 and 2, (HP8644A)
should be used in the setup. These suggested generators have low harmonic distortion and very low phase
noise.
2.High linearity amplifiers to improve isolation. They
prevent the two signal generators from crosstalking
with each other and provide higher output power.
3.A lowpass filter to suppress harmonic content from
interfering with the test signal.
4.The signal combiner (from Mini-Circuits ADP-2-9),
combines the two isolated input signals. This combiner
has a typical isolation of 27dB. For better VSWR and
isolation, use the H-9 signal combiner from MA/COM
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.
5.The attenuator pads, on all three ports of the signal
combiner, will support further isolation of the two input
signal sources. They will reduce reflection and promote
maximum power transfer with wideband impedance
matching.
SETUP AND TESTING SIGNAL SOURCES
Testing Signal Sources
The LTC6430-15 is an amplifier with high linearity performance; therefore, output intermodulation products are very
low. For this reason, it drives most test equipment and test
setups to their limits. Consequently, accurate measurement of the third order intercept point for a low distortion
IC such as the LTC6430-15 requires certain precautions
to be observed in the test setup and testing procedure.
The testing signal should be evaluated and optimized before
it is used for measurements. The following outlines the
necessary steps to achieve optimization.
a. Apply two independent signals f1 and f2 from signal
generator 1 and signal generator 2 at 400MHz and
401MHz while setting amplitude = –13dBm per tone
at the combined output.
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4
DEMO MANUAL DC1774A-B
ADDITIONAL INFORMATION
b.Connect the combined signal directly to the spectrum
analyzer (without the DUT).
c. Adjust the spectrum analyzer for the maximum possible
resolution of the Intermodulation products amplitude
in dBc relative to the main tone power. A narrower
resolution bandwidth will take a longer time to sweep.
Optimize the dynamic range of the spectrum analyzer by
adjusting input attenuation. First increase the spectrum
analyzer input attenuation (normally in steps of 5dB
or 10dB). If the IMD product levels decrease when the
input attenuation is increased, then the input power level
was too high for the spectrum analyzer to make a valid
measurement. In other words, the spectrum analyzer’s
1st mixer was overloaded and produced its own IMD
products. If the IMD reading holds constant with increased input attenuation, then a sufficient amount of
attenuation is present. Adding too much attenuation will
raise the noise floor and bury the intended IMD signal.
Therefore, select just enough attenuation to achieve a
stable and valid measurement.
Testing the DUT
At this point, the input level has been established at –13dBm
per tone, and the input IMD from the test setup is well
suppressed at –96dBm max. Furthermore, the SA is set
up to measure very low level IMD components.
a. Insert the DUT and output attenuator into the setup,
inline between the signal source and SA. The output
attenuator should match the DUT gain.
b.Fine-tune the signal generator levels by a small amount
if necessary (<1dB), to keep output power at 2.0dBm
per tone at the amplifier output.
c. Measure output IMD level using the same optimized
setup as previous. Based on the output power level of
2dBm per tone, and knowing the IMD level, OIP3 can
be calculated.
d.In order to achieve a valid measurement result, the
test system must have lower distortion than the DUT
intermodulation. For example, to measure a 47dBm
OIP3, the measured intermodulation products will be
–90dBc below the –13dBm per tone input level and
the test system must have intermodulation products
approximately –96dBc or better. For best results, the
IMD or noise floor should be at least –100dBc before
connecting the DUT.
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5
DEMO MANUAL DC1774A-B
QUICK START PROCEDURE
Demo circuit 1774A-B can be set up to evaluate the performance of the LTC6430-15. Refer to Figures 4 and 5 for
proper equipment connections and follow the procedure
below:
Single-Tone Measurement
Connect all test equipment as suggested in Figure 4.
1.The power labels of 5V and GND directly correspond
to the power supply. Typical current consumption of
the LTC6430-15 is about 160mA.
2.Apply an input signal to J7. A low distortion, low noise
signal source with an external high order lowpass filter
will yield the best performance. The input C.W. signal
is –10dBm.
3.Observe the output via J8. The measured power at the
analyzer should be about 5dBm.
Two-Tone Measurement
Connect all test equipment as suggested in Figure 5.
1.The power labels of 5V and GND directly correspond
to the power supply. Typical current consumption of
the LTC6430-15 is about 160mA.
2.Apply two independent signals f1 and f2 from SG1 and
SG2 at 400MHz and 401MHz respectively.
3.Monitor the output tone level on the spectrum analyzer.
Adjust signal generator levels such that output power
measures 2dBm/tone at the amplifier output J8, after
correcting for external cable losses 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 399MHz and 402MHz, respectively.
For this setup, the Rohde & Schwarz FSEM30 spectrum
analyzer was used. This SA has a typical 20dBm third
order intercept point (TOI). The Rohde & Schwarz FSU
can also be used. The system as described can measure
OIP3 up to 50dBm.
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DEMO MANUAL DC1774A-B
QUICK START PROCEDURE
ASSY
-A
-B
-C
U1
FREQUENCY
LTC6430AIUF-15 100MHz TO 300MHz
LTC6430AIUF-15 400MHz TO 1000MHz
LTC6431AIUF-15 100MHz TO 1200MHz
DC POWER SUPPLY
GND
V+
VCC = 4.75V TO 5.25V
SIGNAL
(HP8644A)
GENERATOR
LOWPASS
FILTER
(OPT)
3dB
ATTN. PAD
(OPT)
COAXIAL
CABLE
SPECTRUM
ANALYZER
ROHDE & SCHWARZ
FSEM30
Figure 4. Proper Equipment Setup for Gain and Single-Tone Measurement
SIGNAL
(HP8644A)
GENERATOR 1
ASSY
-A
-B
-C
U1
FREQUENCY
LTC6430AIUF-15 100MHz TO 300MHz
LTC6430AIUF-15 400MHz TO 1000MHz
LTC6431AIUF-15 100MHz TO 1200MHz
DC POWER SUPPLY
GND
V+
VCC = 4.75V TO 5.25V
AMPLIFIER
MINI-CIRCUITS ZHL-2
OR EQUIVALENT
LOWPASS
FILTER
6dB ATTN. PAD
(OPT)
COMBINER
MINI-CIRCUITS
ADP-2-9
3dB
ATTN. PAD
6dB ATTN. PAD
(OPT)
COAXIAL
CABLE
APPROX.
–13dBm/TONE
SPECTRUM
ANALYZER
15dB
ROHDE & SCHWARZ
ATTN. PAD
FSEM30
(MATCHES
DUT GAIN)
LOWPASS
FILTER
AMPLIFIER
MINI-CIRCUITS ZHL-2
OR EQUIVALENT
DUT GAIN
APPROX. 15dB
2dBm/TONE
SIGNAL
(HP8644A)
GENERATOR 2
Figure 5. Proper Equipment Setup for IP3 Measurement
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DEMO MANUAL DC1774A-B
PARTS LIST
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART NUMBER
1
4
C1, C3, C7, C20
CAP., X7R, 1000pF, 50V 5%, 0402
AVX, 04025C102JAT2A
2
1
C21
CAP., X7R, 1000pF, 50V 5%, 0603
AVX, 06035C102JAT2A
3
1
C8
CAP., COG, 62pF, 16V 2%, 0402
AVX, 0402YA620GAT2A
4
0
C10, C12
CAP., COG, 62pF, 16V 2%, 0402
OPT
5
0
C11, C13, C16-C19
CAP., X7R, 1000pF, 5%, 0402
OPT
6
1
C22
CAP., X5R, 0.1µF, 10V, 10%, 0603
AVX, 0603ZD104KAT2A
7
2
E3, E6
TESTPOINT, TURRET, 0.064"
MILL-MAX, 2308-2-00-80-00-00-07-0
8
0
JP1
HEADER, 2X6, 0.1"
OPT
9
0
JP2, JP3
HEADER, 2X4, 0.1"
OPT
10
0
J5, J6
CONN., SMA 50Ω EDGE-MOUNTED
OPT
11
1
J7
CONN., SMA 50Ω EDGE-MOUNTED
JOHNSON, 142-0701-851
12
0
J9
CONN., SMA 50Ω EDGE-MOUNTED
OPT
13
2
J11, J18
JACK, BANANA
KEYSTONE, 575-4
14
1
L1
INDUCTOR, CHIP, 560nH, 5%, 0603LS-1608
COILCRAFT, 0603LS-561XJLB
15
0
L11, L22
INDUCTOR, CHIP, 1008LS-2520
OPT
16
1
R2
RES., CHIP, 348Ω, 1%, 0402
YAGEO, RC0402FR-07348RL
17
0
R5, R6
RES., CHIP, 348Ω, 1%, 0402
OPT
18
0
R19
RES., CHIP, 0Ω, 5%, 0402
YAGEO, RC0402JR-070RL
1
1
DC1774A-2
GENERAL BOM
2
2
C2, C4
CAP., X7R, 1000pF, 50V 5%, 0402
AVX, 04025C102JAT2A
3
1
C5
CAP., X7R, 1000pF, 50V 5%, 0603
AVX, 06035C102JAT2A
4
1
C9
CAP., COG, 62pF, 16V 2%, 0402
AVX, 0402YA620GAT2A
5
0
C14, C15
CAP., X7R, 1000pF, 25V 5%, 0402
AVX, 04023C102JAT2A
6
1
C23
CAP., X5R, 0.1µF, 10V, 10%, 0603
AVX, 0603ZD104KAT2A
7
1
L2
INDUCTOR, CHIP, 560nH, 5%, 0603LS-1608
COILCRAFT, 0603LS-561XJLB
8
1
J8
CONN., SMA 50Ω EDGE-MOUNTED
JOHNSON, 142-0701-851
9
0
J10
CONN., SMA 50Ω EDGE-MOUNTED
OPT
10
1
R1
RES., CHIP, 348Ω, 1%, 0402
YAGEO, RC0402FR-07348RL
11
2
R3, R4
RES., CHIP, 0Ω, 1/16W, 5%, 0603
YAGEO, RC0603JR-070RL
12
0
R13, R14, R17, R18
RES., CHIP, 0Ω, 1/16W, 5%, 0603
OPT
13
0
T1, T2
XFMR, MINI-CIRCUITS, ADTL2-18+
OPT
14
2
T3, T4
XFMR, 2:1
MINI CIRCUITS, ADTL2-18+
15
1
U1
IC, IF AMP., QFN24UF-4X4
LINEAR TECH., LTC6430AIUF-15
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DEMO MANUAL DC1774A-B
Figure 6. DC1774A RF/IF AMP/ADC Driver
SCHEMATIC DIAGRAM
dc1774a-bf
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.
9
DEMO MANUAL DC1774A-B
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
dc1774a-bf
10 Linear Technology Corporation
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●
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