Analog Devices UG-396 User manual

Evaluation Board User Guide
UG-396
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 AD5246 Digital Potentiometer
PLEASE SEE THE LAST PAGE FOR AN IMPORTANT
WARNING AND LEGAL TERMS AND CONDITIONS.Rev. 0 | Page 1 of 16
FEATURES
Full-featured board in conjunction with low voltage digiPOT
motherboard (EVAL-MB-LV-SDZ)
Various test circuits
Various ac/dc input signals
PC control via a separately purchased system demonstration
platform (SDP-B or SDP-S)
PC software for control
PACKAGE CONTENTS
EVAL-AD5246DBZ
EVAL-MB-LV-SDZ motherboard
CD that includes
Self-installing software that allows users to control the
board and exercise all functions of the device
Electronic version of the AD5246 data sheet
Electronic version of the UG-396 user guide
GENERAL DESCRIPTION
This user guide describes the evaluation board for evaluating the
AD5246, a single channel, 128-position, digital potentiometer.
The AD5246 supports a single-supply 2.7 V to 5.5 V operation,
making the device suited for battery-powered applications and
many other applications with a superior low temperature
coefficient performance.
In addition, the AD5246 uses a versatile I2C serial interface that
operates in fast mode, allowing speeds of up to 400 kHz.
The E VA L -AD5246DBZ and E VA L -MB-LV-SDZ can operate in
single-supply mode and incorporate an internal power supply
from the USB.
Complete specifications for the AD5246 part can be found in
the AD5246 data sheet, which is available from Analog Devices,
Inc., and should be consulted in conjunction with this user
guide when using the evaluation board.
EVAL-AD5246DBZ WITH MOTHERBOARD AND SDP-B
10624-001
Figure 1. Digital Picture of Evaluation Board with Low Voltage digiPOT Motherboard and System Demonstration Platform

UG-396 Evaluation Board User Guide
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TABLE OF CONTENTS
Features .............................................................................................. 1
Package Contents.............................................................................. 1
General Description ......................................................................... 1
E VA L-AD5246DBZ With Motherboard and SDP-B ................... 1
Revision History ............................................................................... 2
Evaluation Board Hardware ............................................................ 3
Power Supplies .............................................................................. 3
Link Options ................................................................................. 3
Test Circuits................................................................................... 4
Evaluation Board Software...............................................................6
Installing the Software ..................................................................6
Running the Software ...................................................................6
Operating the Software.................................................................7
Schematics and Artwork ..................................................................8
Motherboard ..................................................................................8
Daughter Board .......................................................................... 12
Ordering Information.................................................................... 15
Bill of Materials........................................................................... 15
REVISION HISTORY
5/12—Revision 0: Initial Version

Evaluation Board User Guide UG-396
Rev. 0 | Page 3 of 16
EVALUATION BOARD HARDWARE
POWER SUPPLIES
The EVAL-MB-LV-SDZ supports using single power supplies.
The evaluation board can be powered either from the SDP port
or externally by the J1 and J2 connectors as described in Table 1.
All supplies are decoupled to ground using 10 µF tantalum and
0.1 µF ceramic capacitors.
Table 1. Maximum and Minimum Voltages of the Connectors
Connector No. Label Voltage
J1-1
EXT VDD
Analog positive power supply, V
DD
;
from 2.7 V to 5.5 V.
J1-2 GND Analog ground.
J2-1 VLOGIC Digital supply, from 2.7 V to VDD.
J2-2 DGND Digital ground.
LINK OPTIONS
Several link and switch options are incorporated in the EVAL-
MB-LV-SDZ evaluation board and should be set up before
using the board. Table 2 describes the positions of the links to
control the evaluation board by a PC, via the SDP board. The
functions of these link options are described in detail in Table 3
through Table 5.
Table 2. Link Options Setup for SDP Control (Default)
Link No. Option
A11 3.3 V
A12 AGND
A5 3.3 V
Table 3. Link Functions
Link No. Power Supply Options
A11 VDD This link selects one of the following as the positive power supply:
5 V (from SDP). It is not recommended to power the board with this supply due to SDP voltage limitations.
3.3 V (from SDP).
VDD (external supply from the J1 connector).
A5 VLOGIC This link selects one of the following as the digital supply:
3.3 V (from SDP).
VLOGIC EXT (external supply from the J2 connector).
A12 GND AGND.

UG-396 Evaluation Board User Guide
Rev. 0 | Page 4 of 16
TEST CIRCUITS
The EVAL-AD5246DBZ and EVAL-MB-LV-SDZ incorporate
several test circuits to evaluate the AD5246 performance.
Antilogarithmic DAC
RDAC can be operated as a antilogarithmic DAC, as shown in
Figure 2. R35 should be replaced from the populated value of
0 Ω to the suggested value of 1.5 kΩ.
VOUT1
EXTERNAL
CONNECTION
R34
RDAC
AC+
A
BW
BUF-W1 +
–
A1
B1
W1
V
DD
– V
SS
V
DD
VDD
2
R35
BIAS
V
DD
– V
SS
AGND
2
10624-002
Figure 2. DAC
The output voltage plot is shown in Figure 3. The output voltage
is relative to VAand VB.
1.0
0.8
0.6
0.4
0.2
0
0 20406080100120
DECIMAL CODE
REL
A
TIVE OUTPUT VOLTAGE
10624-003
Figure 3. Antilogarithmic Gain
Table 4 shows the options available for the voltage references.
Table 4. DAC Voltage References
Terminal
Link
(DB1)
Link
(MB2) Options Description
B A2-B A9 AC+
Connects
Terminal A1 to
VDD/2
VDD
Connects
Terminal A1 to
VDD
W A3-B BUF-W1 Connects
Terminal W1
to an output
buffer
R35 A10 BIAS
Connects
Terminal B1 to
VDD/2
AGND
Connects
Terminal B1 to
analog
ground
A1
inserted
1 Daughter board
2 Motherboard
The output voltage is defined in Equation 1.
WB
B
A
OUT RR
R
VVV


35
35
)( (1)
k10
128
 RDAC RWB
where:
RDAC is code loaded in the RDAC register.
VAis the voltage applied to the A terminal (A9 link).
VBis the voltage applied to the B terminal (A10 link).
However, by using the R34 external resistor, the user can reduce
the voltage of the voltage reference. In this case, use the A1 test
point to measure the voltage applied to the A terminal and
recalculate VAin Equation 1.

Evaluation Board User Guide UG-396
Rev. 0 | Page 5 of 16
Signal Amplifier
RDAC can be operated as an inverting or noninverting signal
amplifier supporting linear or pseudo logarithmic gains. Table 5
shows the available configurations.
The noninverting amplifier with linear gain is shown in Figure 4,
and the gain is defined in Equation 3.
R38
R
GWB
 1(2)
where RWB is the resistor between the W and B terminals.
VOUT2
V
IN
RDAC
B
W
+
–
W2
B2
C1
10nF
R41
1.7kΩ
R42
10624-004
R38
2.7kΩ
Figure 4. Linear Noninverting Amplifier
The inverting amplifier with linear gain is shown in Figure 5,
and the gain is defined in Equation 5.
Note that the input signal, VIN, must be negative.
R38
R
GWB
 (3)
where RWB is the resistor between the W and B terminals.
VOUT2
V
IN
RDAC
B
W
+
–
W2
B2
C1
10nF
R41
1.7kΩ
R42
R38
2.7kΩ
10624-005
Figure 5. Linear Inverting Amplifier
Table 5. Amplifier Selection Link Options
Amplifier Gain Link(DB1) Link (MB2) Label VIN Range
Noninverting Linear A2 = A3-A A7 LIN 0 V to VDD
A6 N-INV
A1 not inserted A8 N-INV
Inverting Linear A2 = A3-A A7 LIN −VDD to 0 V
A6 INV
A1 not inserted A8 INV
1Daughter board.
2Motherboard.

UG-396 Evaluation Board User Guide
Rev. 0 | Page 6 of 16
EVALUATION BOARD SOFTWARE
INSTALLING THE SOFTWARE
The E VA L -AD5246DBZ evaluation kit includes evaluation
board software provided on a CD. The software is compatible
with Windows® XP, Windows Vista, and Windows 7 (both
32 bits and 64 bits).
Install the software before connecting the SDP board to the USB
port of the PC to ensure that the SDP board is recognized when
it is connected to the PC. To install the software, use the
following steps:
1. Start the Windows operating system and insert the CD.
2. The installation software opens automatically. If it does
not, run the setup.exe file from the CD.
3. After installation is completed, power up the evaluation
board as described in the Power Supplies section.
4. Connect the EVA L -AD5246DBZ and EVA L -MB-LV-SDZ
into the SDP board and the SDP board into the PC using the
USB cable included in the evaluation kit.
5. When the software detects the evaluation board, follow the
instructions that appear to finalize the installation.
RUNNING THE SOFTWARE
To run the program, use the following steps:
1. Click Start > All Programs > Analog Devices > AD5246
>AD5246 Eval Board. To uninstall the program, click
Start > Control Panel > Add or Remove Programs >
AD5246 Eval Board.
2. If the SDP board is not connected to the USB port when
the software is launched, a connectivity error displays (see
Figure 6). Simply connect the evaluation board to the USB
port of the PC, wait a few seconds, click Rescan, and follow
the instructions.
10624-006
Figure 6. Pop-Up Window Error
3. The main window of the E VA L -AD5246DBZ evaluation
software then opens, as shown in Figure 7.
10624-007
Figure 7. EVAL-AD5246DBZ Evaluation Board Software Main Window

Evaluation Board User Guide UG-396
Rev. 0 | Page 7 of 16
OPERATING THE SOFTWARE
The main window of the E VA L -AD5246DBZ software is divided
into the following sections: RDAC and MANUAL DATA.
RDAC
WRITE can be used to update the RDAC registers by entering a
desirable value into the text box and clicking WRITE. When
WRITE is clicked, a write/read operation is performed, and the
value displayed in this section is updated with the actual RDAC
register value. This function can be used to verify whether the
write operation was completed successfully.
MANUAL WRITE
SEND DATA is a customized I2C data-word can be sent by
manually switching the scroll bars from 0 to 1 or from 1 to 0 as
desired and then clicking SEND DATA.
In addition, the scroll bars are updated on each write transfer,
showing the command sent to the part.
EXIT closes the program.

UG-396 Evaluation Board User Guide
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SCHEMATICS AND ARTWORK
MOTHERBOARD
10624-008
Figure 8. SDP Connector and Power Supply

Evaluation Board User Guide UG-396
Rev. 0 | Page 9 of 16
10624-009
Figure 9. Schematic of Test Circuits

UG-396 Evaluation Board User Guide
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10624-010
Figure 10. Schematic of Connectors to Daughter Board
10624-011
Figure 11. Component Side View