Analog Devices EVAL-AD5781 User manual

Evaluation Board User Guide
UG-184
One Technology Way •P. O. Box 9106 •Norwood, MA 02062-9106, U.S.A. •Tel: [phone] •Fax: [phone] •www.analog.com
Evaluation Board for a 18-Bit Serial Input, Voltage Output DAC
PLEASE SEE THE LAST PAGE FOR AN IMPORTANT
WARNING AND LEGAL TERMS AND CONDITIONS. Rev. 0 | Page 1 of 16
FEATURES
Full-featured evaluation board for the AD5781
Link options
PC control in conjunction with Analog Devices, Inc., system
development platform
PC software for control
EVALUATION BOARD DESCRIPTION
The EVAL-AD5781 is a full-featured evaluation board, designed
to allow the user to easily evaluate all features of the AD5781
voltage output, 18-bit DAC. The AD5781 pins are accessible at
on-board connectors for external connection. The board can be
controlled by two means, via the on-board connector (J6) or via
the system development platform connector (J3). The SDP
board allows the evaluation board to be controlled through the
USB port of a Windows® XP (SP2 or later) or Vista (32-bit)
based PC using the AD5781 evaluation software.
DEVICE DESCRIPTION
The AD5781 is a high precision, 18-bit digital-to-analog con-
verter (DAC), designed to meet the requirements of precision
control applications. The output range of the AD5781 is confi-
gured by two reference voltage inputs. The device is specified to
operate with a dual power supply of up to 33 V.
Complete specifications for the AD5781 are available in the
AD5781 data sheet available from Analog Devices and should
be consulted in conjunction with this user guide when using the
evaluation board.
FUNCTIONAL BLOCK DIAGRAM
POWER SUPPLY INPUTS
SYSTEM DEVELOPMENT
PLATFORM BOARD
PIN HEADER (J6)
PC
USB
PORT
AD5781
POSITIVE
REFERENCE
NEGATIVE
REFERENCE
V
OUT
0
9092-001
Figure 1.

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TABLE OF CONTENTS
Features .............................................................................................. 1
Evaluation Board Description......................................................... 1
Device Description........................................................................... 1
Functional Block Diagram .............................................................. 1
Revision History ............................................................................... 2
Evaluation Board Hardware............................................................ 3
Power Supplies .............................................................................. 3
Link Options ................................................................................. 3
On-Board Connectors ................................................................. 3
Evaluation Board Software...............................................................5
Software Installation .....................................................................5
Software Operation.......................................................................5
Main Window ................................................................................6
Evaluation Board Performance........................................................8
Evaluation Board Schematics and Artwork...................................9
Ordering Information.................................................................... 15
Bill of Materials........................................................................... 15
REVISION HISTORY
8/10—Revision 0: Initial Version

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EVALUATION BOARD HARDWARE
POWER SUPPLIES
The following external supplies must be provided:
•5 V between the VCC and DGND inputs for the digital
supply of the AD5781. Alternatively, place Link 1 in
Position A to power the digital circuitry from the USB
port (default).
•7.5 V to 16.5 V between the VDD and AGND inputs for the
positive analog supply of the AD5781.
•−2.5 V to −16.5 V between the VSS and AGND inputs for
the negative analog supply of the AD5781.
The analog and digital planes are connected at one location,
close to the AD5781. To avoid ground loop problems, it is
recommended not to connect AGND and DGND elsewhere
in the system.
Each supply is decoupled to the relevant ground plane with 10 μF
and 0.1 μF capacitors. Each device supply pin is again decoupled
with a 10 μF and 0.1 μF capacitor pair to the relevant ground plane.
LINK OPTIONS
The link options on the evaluation board should be set for the
required operating setup before using the board. The functions
of the link options are described in Tabl e 5.
Default Link Option Setup
The default link options are listed in Table 1 .
Table 1. Default Link Options
Link No. Option
LK1 A
LK3 A
LK4 Removed
LK5 Removed
LK6 Removed
LK8 A
LK9 C
Connector J6 Pin Descriptions
Table 2. Connector J6 Pin Configuration
9 7 5 3 1
10 8 6 4 2
Table 3. Connector J6 Pin Descriptions
Pin No. Description
1 SDO
2 RESET
3 DGND
4 CLR
5 IOVCC
6 LDAC
7 SDIN
8 DGND
9 SCLK
10 SYNC
ON-BOARD CONNECTORS
There are nine connectors on the AD5781 evaluation board
PCB as outlined in Table 4.
Table 4. On-Board Connectors
Connector Function
J1 Analog power supply connector
J2 Digital power supply connector
J3 SDP board connector
J6 Digital interface pin header connector
VOUT DAC output connector
VOUT_BUF Buffered DAC output connector
VREF 5 V voltage reference input connector (+10 V
and −10 V reference voltages are generated
from 5 V input)
VREFN DAC negative reference input connector
VREFP DAC positive reference input connector

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Table 5. Link Options
Link No. Description
LK1 This link selects the source of the digital power supply.
Position A selects the source from the SDP board.
Position B selects the source from Connector J2.
LK3 This link selects the voltage source for the IOVCC pin.
Position A connects IOVCC to VCC.
Position B selects an externally applied voltage at Pin 5 of J6.
LK4 This link selects the state of the LDAC pin.
When this link is inserted, LDAC is at logic low.
When this link is removed, LDAC is at logic high.
LK5 This link selects the state of the CLR pin.
When this link is inserted, CLR is at logic low.
When this link is removed, CLR is at logic high.
LK6 This link selects the state of the RESET pin.
When this link is inserted, RESET is at logic low.
When this link is removed, RESET is at logic high.
LK8 This link selects the positive reference source.
Position A selects an on-board generated 10 V, derived from 5 V applied at Connector VREF.
Position B selects an external voltage applied at Connector VREFP.
LK9 This link selects the negative reference source.
Position A selects an external voltage applied at Connector VREFN.
Position B selects AGND.
Position C selects an on-board generated −10 V, derived from 5 V applied at Connector VREF.

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EVALUATION BOARD SOFTWARE
SOFTWARE OPERATION
SOFTWARE INSTALLATION
To launch the software, complete the following steps:
The AD5781 evaluation kit includes self-installing software on a
CD. The software is compatible with Windows XP (SP2) and
Vista (32-bit). If the setup file does not run automatically, you
can run setup.exe from the CD.
1. From the Start menu, select Analog Devices – AD5781 >
AD5781 Evaluation Software. The main window of the
software is displayed (see Figure 3).
Install the evaluation software before connecting the evaluation
board and SDP board to the USB port of the PC to ensure that
the evaluation system is correctly recognized when connected to
the PC.
2. If the evaluation system is not connected to the USB port
when the software is launched, a connectivity error is
displayed (see Figure 2). Connect the evaluation board to
the USB port of the PC, wait a number of seconds, and
click Rescan. Follow the instructions.
1. After installation from the CD is complete, power up the
AD5781 evaluation board as described in the Power
Supplies section. Connect the SDP board (Connector A) to
the AD5781 evaluation board and then to the USB port of
your PC using the supplied cable.
0
9092-002
2. When the evaluation system is detected, proceed
through any dialog boxes that appear. This completes
the installation.
Figure 2. Connectivity Error Alert
09092-003
Figure 3. Main Window

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MAIN WINDOW
The main window is divided into three tabs: Configure,
Program Voltage, and Measure DAC Output.
Configure
The Configure section allows access to the control register,
clearcode register, software control register, and DAC register
and also allows control of the RESET, CLR, and LDAC pins.
Program Voltage
The Program Voltage section programs the DAC register with
a value calculated from the entered values: the positive voltage
reference (VREFP), the negative voltage reference (VREFN),
and the desired output voltage (see Figure 4).
09092-004
Figure 4. Program Voltage Window
Measure DAC Output
The Measure DAC Output section allows the PC to control an
Agilent 3458A multimeter to measure and log the DAC output
voltage.
The multimeter is controlled over a general-purpose interface
bus (GPIB). Once connected to the PC, the multimeter should
first be configured via its front panel before taking a measure-
ment. Figure 6 shows the measurement options. The software
runs through a sequence of steps, programming the DAC
register and measuring the DAC output voltage. The sequence
begins with the software programming the DAC with the Start
Code value, incrementing the programmed value at each step
by the Code Step value, and finishing when the programmed
value reaches the Stop Code value. A delay between measure-
ments can be inserted if required. The GPIB address of the
multimeter must be specified.
To begin the measurement, click the START button. The
measurement can be halted at anytime by clicking the STOP
button. When the measurement is completed, a dialog box
appears to allow the data to be saved as a spreadsheet file
with three columns of data. The first column is DAC code,
the second column is DAC voltage in volts, and the third
column is INL error in LSBs, as shown in Figure 5. A graph
of both DAC output voltage vs. DAC code and INL error vs.
DAC code is displayed on-screen (see Figure 6). In the
measurement example shown in Figure 6 measurements are
taken in 256 code steps beginning at Code 0 and finishing
at Code 261,888, in total 1023 measurements. With the number
of power line cycles (NPLC) setting on the multimeter set to 1,
the measurement takes ~75 sec to complete. To complete an all
codes measurement requiring 262,144 measurement points
takes ~6 hours to complete.
09092-006
Figure 5. Saved Data Format
If an Agilent 3458A multimeter is not connected to the PC,
the software steps through the codes without taking any
measurements.

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09092-005
Figure 6. Measure DAC Output Window

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EVALUATION BOARD PERFORMANCE
The following data demonstrates the measured linearity performance of the AD5781 evaluation board circuit. The board is powered from
VDD = +15 V, VSS = −15 V, and VREF = +5 V.
0.5
0.4
0.3
0.2
0.1
–0.4
–0.3
–0.2
–0.1
0
–0.5 0 50k 100k 150k 200k 250k
INL ERROR (LSB)
DAC CODE
09092-007
Figure 7. INL Error vs. DAC Code
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
–0.05
–0.10
–0.15
–0.20
–0.25
–0.30
–0.50
–0.45
–0.40
–0.35
0
20k 40k 60k 80k
100k 120k 140k 160k 180k 200k 220k 240k
262,143
DNL ERROR (LSBs)
DAC CODE
09092-008
Figure 8. DNL Error vs. DAC Code

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EVALUATION BOARD SCHEMATICS AND ARTWORK
09092-009
Figure 9. Schematic of the AD5781 Circuitry

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09092-010
Figure 10. Schematic of the Voltage Reference Scaling Circuitry