Circuit Note
CN-0171
Circuit Designs Using Analog Devices Products
Apply these product pairings quickly and with confidence.
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Devices Connected/Referenced in this Circuit Note
ADL5535/
ADL5536
20 MHz to 1.0 GHz 16 dB/20 dB IF Gain
Block
AD9268
16-Bit, 80 MSPS/105 MSPS/125 MSPS,
1.8 V Dual Analog-to-Digital Converter
Low Noise, Low Distortion Single-Ended Input Drive Circuit for Differential Input IF
Sampling ADCs
CIRCUIT FUNCTION AND BENEFITS
CIRCUIT DESCRIPTION
The circuit shown in Figure 1 uses the ADL5535/ADL5536
single-ended IF low noise 50 Ω gain block to drive the AD9268
16-bit differential input analog-to-digital converter (ADC).
The circuit includes an interstage bandpass filter for noise
reduction and anti-aliasing. The use of a single-ended IF gain
stage followed by a transformer to perform the single-endedto-differential conversion is an optimum solution for this
application where both low noise and low distortion are required.
Figure 1 shows the schematic of the ADL5535/ADL5536
driving the AD9268 16-bit ADC clocked at a sample rate of
122.88 MSPS. The ADL5535 has a single-ended input and
output impedance of 50 Ω. A 1:1 impedance transformer
(M/A-COM BA-007159-000000, 4.5 MHz to 3000 MHz), along
with termination resistors and series ferrite beads, is used to
present a 50 Ω load for the anti-aliasing filter interface. The
filter interface between the ADL5535 and the AD9268 is a
sixth-order Butterworth low-pass filter designed using a
standard filter program. The interface provides a 50 MHz, 1 dB
bandwidth centered around 175 MHz. Following the sixthorder filter, a shunt LC tank circuit (72 nH, 8.2 pF) was inserted
to further reduce the low frequency response of the filter, giving
more of a band-pass response to the filter. The normalized
wideband response is shown in Figure 2.
The ADL5535/ADL5536 is a high linearity (third order output
intercept, OIP3 = +45 dBm at 190 MHz), single-ended, fixed gain
amplifier that can be used as a driver for high performance IF
sampling of analog-to-digital converters. The ADL5535 has a gain
of 16 dB and provides a simple approach to raise the signal from
approximately 400 mV p-p to the 2 V p-p full-scale level required
by the ADC. The ADL5535 low noise figure (3.2 dB at 190 MHz)
and low distortion ensure that the ADC performance is not
compromised. The ADL5536 can be used where a gain of 20 dB is
required.
5V
1.8V
100pF 22nH
68nH
22pF
50Ω
56nH
27pF
8pF
8.2pF
FERRITE BEAD
10Ω AT 100MHz* 66Ω
33Ω
0.1µF
0.1µF
AVDD DRVDD
VIN + A
AD9268
72nH
ADL5535/
ADL5536
1.8V
33Ω
FERRITE BEAD 66Ω
10Ω AT 100MHz*
VIN – A
AGND
0.1µF
*MURATA BLM18BA100SN1
VCM
09229-001
M/A-COM
BA-007159-000000
1
470nH
Figure 1. Schematic of the ADL5535 Driving the AD9268 16-Bit ADC, (Simplified Schematic: All Connections and Decoupling Not Shown)
Rev. 0
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engineers. Standard engineering practices have been employed in the design and construction of
each circuit, and their function and performance have been tested and verified in a lab environment
at room temperature. However, you are solely responsible for testing the circuit and determining its
suitability and applicability for your use and application. Accordingly, in no event shall Analog
Devices be liable for direct, indirect, special, incidental, consequential or punitive damages due to
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©2010 Analog Devices, Inc. All rights reserved.
CN-0171
Circuit Note
The single-tone performance for an input frequency of 170 MHz
and a sampling rate of 122.88 MSPS is shown in Figure 3. Twotone performance is shown in Figure 4.
0
FUNDAMENTAL1 = –7.161dBFS
FUNDAMENTAL2 = –7.116dBFS
IMD (2f1 – f2) = –66.07dBc
IMD (2f2 – f1) = –67.588dBc
NOISE FLOOR = –150.84dBFS/√Hz
–20
–40
5
(dBFS)
–5
–10
–15
–80
–100
–20
–120
–25
–30
–140
0
–35
5
10
15
20
25
30
35
40
FREQUENCY (MHz)
–40
0
50
150
100
200
250
300
350
400
FREQUENCY (MHz)
SAMPLE FREQUENCY = 122.88MHz
SNRFS = 75.877dB
–20 INPUT FREQUENCY = 170MHZ
FUNDAMENTAL POWER = –1.044dBFS
SECOND HARMONIC POWER = –75.499dBc
–40 THIRD HARMONIC POWER = –80.003dBc
NOISE √Hz = –153.762dBFS/√Hz
–60
–80
–100
10
15
20
25
30
35
40
FREQUENCY (MHz)
45
50
55
60
65
09229-003
–120
5
55
60
65
The application circuit described here can be modified for any
IF frequency within the operating range of the ADL5535/ADL5536
and the AD9268. As an alternative to the AD9268, the AD9640,
the AD6657, or the AD9644 can be used for the ADC in this
application.
0
0
50
COMMON VARIATIONS
Figure 2. Normalized Frequency Response of the ADC Interface
Shown in Figure 1
–140
45
Figure 4. Measured Two-Tone Performance of the Circuit Shown
in Figure 1 for Input Tones Centered at 170 MHz and a Sampling Rate
of 122.88 MSPS
09229-002
–45
(dBFS)
–60
09229-004
NORMALIZED RESPONSE (dBFS)
0
Figure 3. Measured Single-Tone Performance of the Circuit Shown
in Figure 1 for an Input Frequency of 17 0MHz and Sampling Frequency
of 122.88 MSPS
Rev. 0 | Page 2 of 3
Circuit Note
CN-0171
LEARN MORE
MT-007 Tutorial, Aperture Time, Aperture Jitter, Aperture Delay
Time—Removing the Confusion, Analog Devices.
AN-742 Application Note. Frequency Domain Response of
Switched Capacitor ADCs. Analog Devices.
AN-827 Application Note. A Resonant Approach to Interfacing
Amplifiers to Switched-Capacitor ADCs. Analog Devices.
CN-0002 Circuit Note, Using the AD8376 VGA to Drive Wide
Bandwidth ADCs for High IF AC-Coupled Applications,
Analog Devices.
CN-0046 Circuit Note, An Ultra Low Distortion Differential
RF/IF Front-End for High Speed ADCs, Analog Devices.
Kester, Walt. High Speed System Applications, Chapter 2
“Optimizing Data Converter Interfaces,” Analog Devices,
2006.
MT-031 Tutorial, Grounding Data Converters and Solving the
Mystery of "AGND" and "DGND," Analog Devices.
MT-073 Tutorial, High Speed Variable Gain Amplifiers (VGAs),
Analog Devices.
MT-075 Tutorial, Differential Drivers for High Speed ADCs
Overview, Analog Devices.
MT-101 Tutorial, Decoupling Techniques, Analog Devices.
Data Sheets and Evaluation Boards
ADL5535
ADL5536
AD9268
AD9268 Evaluation Board
REVISION HISTORY
10/10—Revision 0: Initial Version
(Continued from first page) Circuits from the Lab circuits are intended only for use with Analog Devices products and are the intellectual property of Analog Devices or its licensors. While you
may use the Circuits from the Lab circuits in the design of your product, no other license is granted by implication or otherwise under any patents or other intellectual property by
application or use of the Circuits from the Lab circuits. Information furnished by Analog Devices is believed to be accurate and reliable. However, "Circuits from the Lab" are supplied "as is"
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purpose and no responsibility is assumed by Analog Devices for their use, nor for any infringements of patents or other rights of third parties that may result from their use. Analog Devices
reserves the right to change any Circuits from the Lab circuits at any time without notice but is under no obligation to do so.
©2010 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
CN09229-0-10/10(0)
Rev. 0 | Page 3 of 3