Circuit Note
Circuit Designs Using Analog Devices Products
Apply these product pairings quickly and with confidence.
For more information and/or support call 1-800-AnalogD
(1-800-262-5643) or visit www.analog.com/circuits.
Devices Connected/Referenced in this Circuit Note
ADL5535/
ADL5536
AD9268
20 MHz to 1.0 GHz 16 dB/20 dB IF Gain
Block
16-Bit, 80 MSPS/105 MSPS/125 MSPS,
1.8 V Dual Analog-to-Digital Converter
CN-0171
Low Noise, Low Distortion Single-Ended Input Drive Circuit for Differential Input IF
Sampling ADCs
CIRCUIT FUNCTION AND BENEFITS
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-ended-
to-differential conversion is an optimum solution for this
application where both low noise and low distortion are required.
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
470nH
100pF 22nH
50Ω
68nH
22pF
56nH
27pF
8pF
72nH
M/A-COM
BA-007159-000000
1
8.2pF
33Ω
FERRITE BEAD
10Ω
AT 100MHz*
66Ω
1.8V
CIRCUIT DESCRIPTION
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 sixth-
order 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.
0.1µF
AVDD DRVDD
VIN + A
AD9268
33Ω
FERRITE BEAD 66Ω
10Ω
AT 100MHz*
0.1µF
VIN – A
AGND
VCM
ADL5535/
ADL5536
0.1µF
*MURATA BLM18BA100SN1
Figure 1. Schematic of the ADL5535 Driving the AD9268 16-Bit ADC, (Simplified Schematic: All Connections and Decoupling Not Shown)
Rev. 0
“Circuits from the Lab” from Analog Devices have been designed and built by Analog Devices
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
any cause whatsoever connected to the use of any“Circuit from the Lab” (Continued on last page)
.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113
©2010 Analog Devices, Inc. All rights reserved.
09229-001
CN-0171
The single-tone performance for an input frequency of 170 MHz
and a sampling rate of 122.88 MSPS is shown in Figure 3. Two-
tone performance is shown in Figure 4.
5
0
Circuit Note
0
–20
–40
–60
–80
–100
–120
FUNDAMENTAL1 = –7.161dBFS
FUNDAMENTAL2 = –7.116dBFS
IMD (2f1 – f2) = –66.07dBc
IMD (2f2 – f1) = –67.588dBc
NOISE FLOOR = –150.84dBFS/√Hz
NORMALIZED RESPONSE (dBFS)
–5
–10
–15
–20
–25
–30
–35
–40
0
50
100
150
200
250
300
350
400
09229-002
(dBFS)
0
5
10
15
20
25
30
35
40
45
50
55
60
65
FREQUENCY (MHz)
–45
FREQUENCY (MHz)
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
Figure 2. Normalized Frequency Response of the ADC Interface
Shown in Figure 1
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
0
COMMON VARIATIONS
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.
(dBFS)
–60
–80
–100
–120
0
5
10
15
20
25
30
35
40
45
50
55
60
65
FREQUENCY (MHz)
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
09229-003
–140
Rev. 0 | Page 2 of 3
09229-004
–140
Circuit Note
LEARN MORE
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.
CN-0171
MT-007 Tutorial,
Aperture Time, Aperture Jitter, Aperture Delay
Time—Removing the Confusion,
Analog Devices.
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"
and without warranties of any kind, express, implied, or statutory including, but not limited to, any implied warranty of merchantability, noninfringement or fitness for a particular
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
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
