Analog Devices PulSAR AD7685 User manual

8-/10-Lead PulSAR User Guide
UG-340
One Technology Way •P. O. Box 9106 •Norwood, MA 02062-9106, U.S.A. •Tel: [phone] •Fax: [phone] •www.analog.com
Evaluation Board for the 8-/10-Lead Family of 14-/16-/18-Bit PulSAR ADCs
PLEASE SEE THE LAST PAGE FOR AN IMPORTANT
WARNING AND LEGAL TERMS AND CONDITIONS. Rev. C | Page 1 of 31
FEATURES
Full featured evaluation board for 8-/10-lead PulSAR ADCs
Versatile analog signal conditioning circuitry
On-board reference, reference buffers, and ADC drivers
PC software for control and data analysis of time and
frequency domain
System demonstration platform compatible (EVAL-SDP-CB1Z)
EQUIPMENT NEEDED
Evaluation board (see Table 5)
Wall adapter power supply
Additional equipment needed
SDP board (EVAL-SDP-CB1Z) (optional)
Precision source
Cable (SMA input to evaluation board)
GENERAL DESCRIPTION
The 10-lead PulSAR® evaluation board covers the following
10-lead PulSAR analog-to-digital converters (ADCs): AD7685
(16-bit), AD7686 (16-bit), AD7687 (16-bit), AD7688 (16-bit),
AD7690 (18-bit), AD7691 (18-bit), AD7693 (16-bit), AD7942
(14-bit), AD7946 (14-bit), AD7980 (16-bit), AD7982 (18-bit),
AD7983 (16-bit), AD7984 (18-bit), AD7988-5 (16-bit), AD7989-5
(18-bit), AD7915 (16-bit) and AD7916 (16-bit).
The 8-lead PulSAR evaluation board covers the following 8-lead
PulSAR ADCs: AD7683 (16-bit), AD7684 (16-bit), and AD7694
(16-bit).
These low power ADCs offer very high performance of up to
18 bits with throughputs ranging from 100 kSPS to 1.33 MSPS.
The evaluation board is designed to demonstrate the performance
of the ADCs and to provide an easy to understand interface
for a variety of system applications. A full description of these
products is available in their respective data sheets, which
should be consulted when using this evaluation board.
The evaluation board is ideal for use with Analog Devices, Inc.,
system demonstration platform (SDP). This evaluation board
interfaces to the SDP board via a 120-pin connector. SMA
connectors, J6 and J10, are provided for the low noise analog
signal source.
On-board components include a high precision buffered band gap
5.0 V reference (ADR435), a signal conditioning circuit with two
op amps (ADA4841-1), and a power supply to derive the necessary
voltage levels to supply all voltage needs. The 8-lead board also
includes a level shifter (ADG3304) to interface the ADC with
the EVAL-SDP-CB1Z.
SIMPLIFIED EVALUATION BOARD BLOCK DIAGRAM
SDP BOARD10-LEAD PulSAR EVALUATION BOARD
VIN+
VIN–
IN+
IN–
ADC
+V
S
–V
S
GND
5V
ADSP-BF527
DSP
SPORT
SCK
SDO
CNV
OVDD
SDI
REF
+7.5V VDD
ADA4841-1
ADA4841-1
AB
–2.5V
–2.5V
+7.5V GND
VCM
AD8031
POWER SUPPLY CIRCUITRY
ADP7102, ADP7104, ADP2301
VIN = 9V
WALL ADAPTER
VDD
VSDP
GND
(OPTIONAL)
(OPTIONAL)
+7.5V/-2.5V 2.5V/5V +7.5V 3.3V +5V
ADR435
5V
GLUE
LOGIC
10322-001
Figure 1.

UG-340 8-/10-Lead PulSAR User Guide
TABLE OF CONTENTS
Features .............................................................................................. 1
Equipment Needed........................................................................... 1
General Description ......................................................................... 1
Simplified Evaluation Board Block Diagram................................ 1
Revision History ............................................................................... 2
Evaluation Board Kit Contents ....................................................... 3
Hardware Requirements .................................................................. 3
Evaluation Board Hardware ............................................................ 4
Setting Up the Evaluation Board................................................ 4
Power Supplies .............................................................................. 4
Reference ....................................................................................... 4
Serial Interface .............................................................................. 4
Solder Links................................................................................... 4
Analog Inputs................................................................................ 4
Evaluation Board Software.............................................................. 5
Installing the Software ................................................................. 5
Installation Steps........................................................................... 5
Board Operation/Connection Sequence................................... 7
Running the Software with the Hardware Connected .............7
Running the Software Without Hardware .................................8
Software Operation ...........................................................................9
Description of User Panel ......................................................... 10
Waveform Capture ..................................................................... 11
AC Tes ting—Histogram ............................................................ 12
DC Testing—Histogram............................................................ 13
AC Tes ting—FFT Capture ........................................................ 13
Summary Tab.............................................................................. 14
Save File ....................................................................................... 15
Load File ...................................................................................... 15
Evaluation Board Schematics........................................................ 16
Troubleshooting.............................................................................. 29
Software ....................................................................................... 29
Hardware ..................................................................................... 29
Products on this Evaluation Board .............................................. 30
Related Links............................................................................... 30
REVISION HISTORY
3/15—Rev. B to Rev. C
Changes to General Description Section ...................................... 1
Changes to Table 3............................................................................ 4
Changes to Table 5.......................................................................... 30
2/14—Rev. A to Rev. B
Changes to Equipment Needed Section and General
Description Section.......................................................................... 1
Changes to Evaluation Kits Contents Section .............................. 3
Change to Table 3 ............................................................................. 4
Changes to Table 5.......................................................................... 30
10/12—Rev. 0 to Rev. A
Added 8-Lead PulSAR Evaluation Board .......................Universal
Changes to Description of User Panel Section........................... 10
Changes to Figure 27 Caption ...................................................... 16
Added Figure 28; Renumbered Sequentially .............................. 17
Changes to Figure 36 Caption and Figure 37 Caption .............. 23
Changes to Figure 38 Caption and Figure 39 Caption .............. 24
Changes to Figure 40 Caption ...................................................... 25
Added Figure 41 and Figure 42 .................................................... 26
Added Figure 43 and Figure 44 .................................................... 27
Added Figure 45 ............................................................................. 28
Changes to Software Section......................................................... 29
Changes to Table 5 and Related Links Section ........................... 30
5/12—Revision 0: Initial Version
Rev. C | Page 2 of 31

8-/10-Lead PulSAR User Guide UG-340
EVALUATION BOARD KIT CONTENTS
Evaluation board for ADC of your choice
(U1 device is specific to the evaluation board ordered)
Business card with Analog Devices website address for
software and documentation
9 V wall wart
HARDWARE REQUIREMENTS
9 V wall wart (supplied)
Standard USB A to Mini-B USB cable
Signal source, ac source with low distortion, and dc source
with low noise
Band-pass filter suitable for 16- and 18-bit testing (value
based on signal frequency)
SDP board for data transfer to PC
Signal source and cables
Rev. C | Page 3 of 31

UG-340 8-/10-Lead PulSAR User Guide
EVALUATION BOARD HARDWARE
SETTING UP THE EVALUATION BOARD
Figure 27 shows the evaluation board schematic. The board
consists of the ADC, U1, with a reference, U6 (ADR435), and
ADC drivers, U12 and U14 (ADA4841-1). The 8-lead board
also has a level shifter, U16 (ADG3304).
The evaluation board is a flexible design that enables the user to
adjust compensation components in addition to operating from
an adjustable bench top power supply.
POWER SUPPLIES
The evaluation board requires power from a wall adapter. The
on-board power supply design is designed to operate from 9 V.
Table 1. Power Supplies Provided on the Board
Power Supply (V) Function Components Used
+5 SDP power ADP2301
+7.5 Positive rail ADP7102
−2.5 Negative rail ADP2301
+2.5/+5 ADC ADP7104
+3.3 VDRIVE (digital power) ADP7104
Each supply is decoupled where it enters the board and again at
each device. A single ground plane is used on this board to
minimize the effect of high frequency noise interference.
In addition to this, there is also the ability to power the board
from a bench top power supply. The screw terminals, J2 and J3, are
provided for this function. When bench power is used, the wall
wart and on-board power supply are no longer required. Solder
links also must be changed: SL1 = B, SL2 = B, SL7 = B, SL4 = B,
and SL3 = B.
REFERENCE
An external 5 V reference (U6, ADR435) is used to supply the
ADCs directly.
SERIAL INTERFACE
The evaluation board uses the SPORT interface from the ADSP-
BF527 D S P.
A number of AND gates are used to clock and gate the SPORT
transfer to the ADC device. See U9, U10, and U11. The 8-lead
board also has a level shifter, U16 (ADG3304), which interfaces
the ADC logic levels (5 V) to the E VA L -SDP-CB1Z (3.3 V).
SOLDER LINKS
There is one three solder link option on the board. It is configured
depending on which generic of the ADC is on the specific
evaluation board as described in Table 3.
Table 2. Table of Jumper Detail with Factory Default Setting
Link Setting Function Comment
SL2 A −VSChange to B if using bench supplies
SL1 A +VSChange to B if using bench supplies
SL3 A V_SDP Change to B if using bench supplies
SL7 A VDD for
ADC
Change to B if using bench supplies
SL4
A
VREF
Change to B if using bench supplies
Table 3. Table of Jumpers Specific to Different ADCs
Link Setting Configuration Generic
SL10 A Differential
input
AD7684, AD7687, AD7688,
AD7690, AD7691, AD7693,
AD7982, AD7984, AD7989-5,
AD7915, AD7916
SL10 B Single-ended AD7683, AD7685, AD7686,
AD7694, AD7942, AD7946,
AD7980, AD7983, AD7988-5
ANALOG INPUTS
The analog inputs to the evaluation board are SMA connectors,
J6 and J10. These inputs are buffered with dedicated amplifier
circuitry (U12 and U14), as shown in Figure 27. The circuit allows
different configurations, input range scaling, filtering, addition of a
dc component, and use of different op amp and supplies. The
analog input amplifiers are set as unity-gain buffers at the factory.
The amplifier positive rail is driven from 7.5 V (from U13,
ADP7102). The negative amplifier rail is driven from –VS
(generated by U3, ADP2301).
The default configuration sets both U12 and U14 at midscale,
generated from a buffered reference voltage divider (VCM).
The evaluation board is factory configured for providing either
a single-ended path or a fully differential path as shown in Table 3.
For dynamic performance, a fast Fourier transform (FFT) test
can be done by applying a very low distortion ac source.
For low frequency testing, the audio precision source can be used
directly because the outputs on these are isolated. Set the outputs
for balanced and floating ground. Different sources can be used;
however, most are single-ended sources that use a fixed output
resistance.
Because the evaluation board uses the amplifiers in unity-gain,
the noninverting input has a common-mode input with a series
590 Ω resistor, and it needs to be taken into account when directly
connecting a source (voltage divider).
Rev. C | Page 4 of 31

8-/10-Lead PulSAR User Guide UG-340
Rev. C | Page 5 of 31
EVALUATION BOARD SOFTWARE
INSTALLING THE SOFTWARE
The evaluation board software can be downloaded from the
relevant product page on the Analog Devices website.
Install the software prior to connecting the SDP board to the USB
port of the PC. This ensures that the SDP board is recognized
when it connects to the PC.
1. Start the Windows® operating system and download the
software from the relevant product page on the Analog
Devices website.
2. Unzip the downloaded file. Run the setup.exe file.
3. After installation is completed, power up the evaluation
board as described in the Power Supplies section.
4. Plug the evaluation board into the SDP board and the SDP
board into the PC using a USB cable.
5. When the software detects the evaluation board, proceed
through any dialog boxes that appear to finalize the
installation.
The default location for the software is the following:
C:\Program Files\Analog Devices\8 & 10 Lead PulSAR ADCs.
This location contains the executable software and example files.
INSTALLATION STEPS
Proceed through the installation, allowing the software and
drivers to be placed in the appropriate locations. Connect the
SDP board to the PC only after the software and drivers have
been installed.
There are two parts to the software installation. First, install the
software related to the evaluation board, as shown in Figure 2 to
Figure 7.
10322-002
Figure 2. Evaluation Board Software Installation Launches
10322-003
Figure 3. Choose Folder Location, Default Folder Shown
10322-004
Figure 4. Accept National Instruments Software License Agreement
10322-005
Figure 5. Click Next >> to Install Software

UG-340 8-/10-Lead PulSAR User Guide
Rev. C | Page 6 of 31
10322-006
Figure 6. Bar Showing Installation Progress
10322-007
Figure 7. Installation Complete, Click Next >> to Complete and Finish
The second part of the software installation is the drivers related to
the SDP board. These drivers must be installed for the evaluation
board to function correctly. See Figure 8 to Figure 12.
10322-008
Figure 8. Installation for SDP Starting
10322-009
Figure 9. Click Next > to Install the ADI SDP Drivers
10322-010
Figure 10. Choose Install Location, Default Folder Shown
10322-011
Figure 11. Installation in Progress

8-/10-Lead PulSAR User Guide UG-340
Rev. C | Page 7 of 31
10322-013
Figure 12. Click Finish to Complete Installation
When you first plug in the SDP board via the USB cable provided,
allow the new Found Hardware Wizard to run. You can check
that the drivers and the board are connected correctly by looking at
the Device Manager of the PC. The Analog Devices System
Development Platform (32MB) should appear under ADI
Development Tools.
10322-014
Figure 13. Device Manager
BOARD OPERATION/CONNECTION SEQUENCE
The following is the board operation/connection sequence:
1. Connect the SDP controller board to the evaluation board
with the J5 connector (screw into place as required). The
software is configured to find the evaluation board on either
connector of the SDP board.
2. Power the board with the appropriate supply as described
in the Power Supplies section.
3. Connect to the PC with the USB cable.
4. Launch the software. Click Start > All Programs >
Analog Devices > 8 & 10 Lead PulSAR ADCs.
5. Apply signal source and capture data.
RUNNING THE SOFTWARE WITH THE HARDWARE
CONNECTED
To run the program, take the following steps:
1. Click Start > All Programs > Analog Devices > 8 & 10
Lead PulSAR ADCs. To uninstall the program, click Start
> Control Panel > Add or Remove Programs > Analog
Devices 8 & 10 Lead PulSAR ADCs.
2. If the SDP board is not connected to the USB port when
the software is launched, a connectivity error displays (see
Figure 14). Connect the evaluation board to the USB port of
the PC, wait a few seconds, click Rescan, and follow the
instructions.
10322-015
Figure 14. SDP Board Not Connected to the USB Port Pop-Up Window Error
3. When evaluation board is detected, Figure 15 displays.
Click OK to continue.
10322-016
Figure 15. Software Detects Evaluation Board
4. The software then connects to the board and displays what
is shown in Figure 16.
10322-017
Figure 16. Software Connects to SDP Board
5. When the board is correctly detected, the software panel
opens.

UG-340 8-/10-Lead PulSAR User Guide
Rev. C | Page 8 of 31
RUNNING THE SOFTWARE WITHOUT HARDWARE
The software can run in standalone mode when no evaluation
board hardware is connected to the USB port.
1. Click Start > All Programs > Analog Devices > 8 & 10
Lead PulSAR ADCs.
2. The software automatically seeks to find the hardware
connected; therefore, when no hardware is connected, it
displays a connectivity error (see Figure 17). To continue
without hardware in standalone mode, click Cancel.
10322-018
Figure 17. No Hardware Connected Pop-Up Window Error
3. The software alerts you that no hardware is connected, and
that the software will continue in standalone mode.
10322-019
Figure 18. Software Indicates Operating in Standalone Mode
4. Within standalone/offline mode, you can load example
files or previously saved files and analyze these files.
5. If you decide to connect hardware at this point, close the
software and relaunch it to allow the software to search for
the board again.

8-/10-Lead PulSAR User Guide UG-340
Rev. C | Page 9 of 31
SOFTWARE OPERATION
When the software launches, the panel opens and the software
looks for the hardware connected to the PC. The software
detects the generic attached to the PC (see Figure 19). The
product panel then launches.
10322-020
Figure 19. Software Detects AD7691
2
3
4
5
67 8 9
10
1
10322-021
Figure 20. Setup Screen

UG-340 8-/10-Lead PulSAR User Guide
Rev. C | Page 10 of 31
DESCRIPTION OF USER PANEL
The following is the description of the user panel:
1. File menu with choice of
a. Load Data: load previously captured data
b. Save Data as .tsv: save captured data in tsv (tab
separated values) format for future analysis
c. Save Picture: use to save the current screen capture
d. Print
e. Exit
2. When hardware is connected to the USB port, the software
automatically detects which generic is connected and displays
it here. Without hardware, the software can be operated in
standalone mode for data analysis, and the device information
notes the device number pulled from the saved data file.
3. Sampling Frequency: The default sampling frequency
matches the maximum sample rate of the ADC connected
to the board. The user can adjust the sampling frequency;
however, there are limitations around the sample frequency
related to the SCLK frequency applied. The sample frequency
must be an integer divider of the SCLK frequency. In addition,
where unusable sample frequencies are input, the software
automatically adjusts the sample frequency accordingly.
Units can be entered, such as 10k for 10,000 Hz. Because
the maximum sample frequency possible is device dependent,
with some of the ADCs capable of operating up to 250 kSPS,
while others can go to 1.3 MSPS, the software matches the
particular ADC ability. If the user enters a value larger than
the ability of the existing device, the software indicates this
and reverts to the maximum sample frequency.
4. sCLK Frequency: The default SCLK frequency is set to
60 MHz, which is the maximum allowable from the SDP.
The SCLK is applied to the ADC SCK pin. The SDP board
limits the SCLK frequency; nominal values for correct
operation are 60 MHz, 30 MHz, and 20 MHz. Where the
user adjusts the SCLK/sample rate to values that are not
supported by the SDP clock or the ADC sample rate, the
software overrides by adjusting values accordingly and
identify this to the user (see Figure 21). The SCLK frequency
is rounded down.
10322-022
Figure 21. Software Overwritten User Settings to a Sample Rate/SCLK Rate
Suitable for SDP Data Transfer
5. External Reference Voltage. By default, this reference is 5 V
(ADR435 on-board reference). The minimum/maximum
voltage calculations are based on this reference voltage. If
the user changes the reference voltage, this input must be
changed accordingly.
6. Click Read to perform a single capture.
7. Click Start Stream to perform a continuous capture from
the ADC.
8. Click Stop Stream to stop streaming data.
9. Select the number of samples (Num Samples) to analyze.
10. There are four tabs available that display the data in
different formats:
a. Waveform
b. Histogram
c. FFT
d. Summary
To exit the software, go to File > Exit or use the EXIT button in
the bottom left corner.
Within any of the chart panels, the tools shown in Table 4 allow
user control of the different chart displays.
Table 4.
Symbol Description
This tool is used to control the cursor, if present.
This tool is used to zoom in and out.
This tool is used for panning.
To save t he pl ot, cli ck Save Plot.

8-/10-Lead PulSAR User Guide UG-340
Rev. C | Page 11 of 31
WAVEFORM CAPTURE
Figure 22 illustrates the waveform capture. The input signal is a 1 kHz sine wave. The waveform analysis reports the amplitudes recorded
from the captured signal in addition to the frequency of the signal tone.
1
10322-023
Figure 22. Waveform Tab

UG-340 8-/10-Lead PulSAR User Guide
Rev. C | Page 12 of 31
AC TESTING—HISTOGRAM
The ac testing histogram tests the ADC for the code distribution
for the ac input, computes the mean and standard deviation, or
transition noise, of the converter, and displays the results. Raw data
is captured and passed to the PC for statistical computations. To
perform a histogram test, select Histogram and click Start Stream.
Note that an ac histogram needs a quality signal source applied
to the input J6/J10 connectors. Figure 23 shows the histogram
for a 1 kHz sine wave applied to the ADC input.
Figure 23 shows the histogram results for the signal applied. It
also illustrates the different measured values for the data captured
(see Number 1 within Figure 23).
1
10322-024
Figure 23. Histogram Tab, Histogram Captured for Sine Wave

8-/10-Lead PulSAR User Guide UG-340
Rev. C | Page 13 of 31
DC TESTING—HISTOGRAM
More commonly, the histogram is used for dc testing where the
user tests the ADC for the code distribution for dc input, computes
the mean and standard deviation, or transition noise, of the
converter, and displays the results. Raw data is captured and
passed to the PC for statistical computations. To perform a
histogram test, select Histogram and click Start Stream. Note
that a histogram test can be performed without an external
source because the evaluation board has a buffered VREF/2
source at the ADC input. To test other dc values, apply a source
to the J6/J10 inputs. It may be required to filter the signal to
make the dc source noise compatible with that of the ADC.
AC TESTING—FFT CAPTURE
This tests the traditional ac characteristics of the converter and
displays an FFT of the result. As in the histogram test, raw data
is captured and passed to the PC where the FFT is performed
displaying signal-to-noise ratio (SNR), signal-to-noise-and-
distortion ratio (SINAD), total harmonic distortion (THD),
and spurious-free dynamic range (SFDR). The data can also
be displayed in the time domain. To perform an ac test, apply
a sinusoidal signal to the evaluation board at the SMA inputs,
J6/J10. Low distortion, better than 100 dB, is required to allow
true evaluation of the device. One possibility is to filter the input
signal from the ac source. A band-pass filter can be used, and
its center frequency must match the test frequency of interest.
Furthermore, if using a low frequency band-pass filter when
the full-scale input range is more than a few V p-p, use the on-
board amplifiers to amplify the signal, thus preventing the filter
from distorting the input signal.
Figure 24 displays the histogram of the captured data that includes
the following:
The spectrum information
The fundamental frequency and amplitude in addition to
the second-to-fifth harmonics
The performance data (SNR, dynamic range, THD,
SINAD, and noise performance)
1
2 3
10322-025
Figure 24. FFT Tab

UG-340 8-/10-Lead PulSAR User Guide
Rev. C | Page 14 of 31
SUMMARY TAB
The Summary tab captures all the display information and provides them in one panel with a synopsis of the information including key
performance parameters, such as SNR and THD.
10322-026
Figure 25. Summary Tab, Shows All Captured Windows

8-/10-Lead PulSAR User Guide UG-340
Rev. C | Page 15 of 31
SAVE FILE
The software can save the current captured data for later analysis,
and the file format is .tsv (tab separated values).
The user is prompted with a Choose or Enter Path of File box
(see Figure 26); save to an appropriate folder location.
10322-027
Figure 26. Save Dialog Box
LOAD FILE
The user is prompted with a Load File box. The user may have to
navigate to find these example files. The default location for the
example files is C:\Program Files\Analog Devices\8 & 10 Lead
PulSAR ADCs\Example files.

UG-340 8-/10-Lead PulSAR User Guide
EVALUATION BOARD SCHEMATICS
10322-128
Figure 27. 10-Lead Evaluation Board, ADC and Driver
Rev. C | Page 16 of 31

8-/10-Lead PulSAR User Guide UG-340
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Figure 28. 8-Lead Evaluation Board, ADC and Driver
Rev. C | Page 17 of 31

UG-340 8-/10-Lead PulSAR User Guide
Rev. C | Page 18 of 31
10322-129
Figure 29. Voltage Reference and Common-Mode Buffer
10322-130
Figure 30. Secondary Power Connector for Bench Supply Purposes

8-/10-Lead PulSAR User Guide UG-340
10322-131
Figure 31. On-Board Amplifier Power Supply, +7.5/−2.5 V
Rev. C | Page 19 of 31

UG-340 8-/10-Lead PulSAR User Guide
Rev. C | Page 20 of 31
10322-132
Figure 32. SDP Power Supply
10322-133
Figure 33. ADC/VDRIVE Power Supply