CN-0259 Datasheet, PDF (4/5 Pages) Analog Devices – High Performance 65 MHz Bandwidth Quad IF Receiver with Antialiasing Filter and 184.32 MSPS Sampling Rate

CN-0259
Circuit Note
The SFDR performance in this design is determined by two
factors: the amplifier and the ADC interface component values,
as shown in Figure 1. The final SFDR performance numbers
shown in Table 1 and Figure 5 were obtained after optimizing
the filter design to account for the board parasitics and nonideal
components used in the filter design.
Another trade-off that can be made in this particular design is
the ADC full-scale setting. The full-scale ADC differential input
voltage was set for 1.75 V p-p for the data obtained with this design,
which optimizes SFDR. Changing the full-scale input range to
2.0 V p-p yields a small improvement in SNR, but slightly degrades
the SFDR performance. Changing the full-scale input range in
the opposite direction to 1.5 V p-p yields a small improvement
in SFDR but slightly degrades the SNR performance.
Note that the signal in this design is ac coupled with the 0.1 µF
capacitors to block the common-mode voltages between the
amplifier, its termination resistors, and the ADC inputs. Refer
to the AD6657A data sheet for further details regarding
common-mode voltages.
Passive Component and PC Board Parasitic
Considerations
The performance of this or any high speed circuit is highly
dependent on proper PCB layout. This includes, but is not limited
to, power supply bypassing, controlled impedance lines (where
required), component placement, signal routing, and power and
ground planes. See the MT-031 and MT-101 tutorials for more
detailed information regarding PCB layout for high speed ADCs
and amplifiers.
Use low parasitic surface-mount capacitors, inductors, and
resistors for the passive components in the filter. The inductors
chosen are from the Coilcraft 0603CS series. The surface-mount
capacitors used in the filter are 5%, C0G, 0402-type for stability
and accuracy.
See the CN-0259 Design Support Package (www.analog.com/
CN0259-DesignSupport) for complete documentation on the
system.
COMMON VARIATIONS
For applications that require less bandwidth and lower power,
the ADL5562 differential amplifier can be used. The ADL5562
has a bandwidth of 3.3 GHz. For even lower power and bandwidth,
the ADA4950-1 could also be used. This device has a 1 GHz
bandwidth and only uses 10 mA of current.
CIRCUIT EVALUATION AND TEST
This circuit uses the EVAL-CN0259-HSCZ circuit board and
the HSC-ADC-EVALCZ FPGA-based data capture board. The
two boards have mating high speed connectors, allowing for the
quick setup and evaluation of the circuit's performance. The
EVAL-CN0259-HSCZ board contains the circuit evaluated as
described in this note, and the HSC-ADC-EVALCZ data capture
board is used in conjunction with Visual Analog evaluation
software, as well as the SPI Controller software to properly
control the ADC and capture the data. See the CN0259 Design
Support package for the schematic, BOM, and layout files for
the EVAL-CN0259-HSCZ board. Application Note AN-835
contains complete details on how to set up the hardware and
software to run the tests described in this circuit note.
LEARN MORE
CN-0259 Design Support Package:
http://www.analog.com/CN0259-DesignSupport
UG-232: Evaluating the AD6642/AD6657 Analog to Digital
Converters
Alex Arrants, Brad Brannon and Rob Reeder, AN-835
Application Note: Understanding High Speed ADC Testing
and Evaluation, Analog Devices.
Ardizzoni, John. A Practical Guide to High-Speed Printed-Circuit-
Board Layout, Analog Dialogue 39-09, September 2005.
MT-031 Tutorial, Grounding Data Converters and Solving the
Mystery of “AGND” and “DGND”, Analog Devices.
MT-101 Tutorial, Decoupling Techniques, Analog Devices.
Agilent Technologies, Advanced Design System.
Reeder, Rob, Frequency Domain Response of Switched Capacitor
ADCs, AN-742 Application Note, Analog Devices.
Reeder, Rob, Achieve CM Convergence between Amps and ADCs,
Electronic Design, July 2010.
Reeder, Rob, Mine These High-Speed ADC Layout Nuggets For
Design Gold, Electronic Design, September 15, 2011.
Rarely Asked Questions: Considerations of High-Speed
Converter PCB Design, Part 1: Power and Ground Planes,
Design News, November 2010.
Rarely Asked Questions: Considerations of High-Speed
Converter PCB Design, Part 2: Using Power and Ground
Planes to Your Advantage, Design News, February 2011
Rarely Asked Questions: Considerations of High-Speed
Converter PCB Design, Part 3: The E-Pad Low Down, Design
News, June 2011
Data Sheets and Evaluation Boards
CN-0259 Circuit Evaluation Board (EVAL-CN0259-HSCZ)
Standard Data Capture Platform (HSC-ADC-EVALCZ)
AD6657A Data Sheet
ADL5565 Data Sheet
AD6657A Evaluation Board (AD6657AEBZ)
Rev. B | Page 4 of 5