Analog Devices EVAL-AD5142DBZ User manual

Evaluation Board User Guide
UG-471
One Technology Way •P. O. Box 9106 •Norwood, MA 02062-9106, U.S.A. •Tel: [phone] •Fax: [phone] •www.analog.com
Evaluating the AD5142 Digital Potentiometer
PLEASE SEE THE LAST PAGE FOR AN IMPORTANT
WARNING AND LEGAL TERMS AND CONDITIONS.Rev. 0 | Page 1 of 20
FEATURES
Full featured evaluation 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-AD5142DBZ board
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 AD5142 data sheet
Electronic version of the UG-471 user guide
GENERAL DESCRIPTION
This user guide describes the evaluation board for evaluating the
AD5142—a quad-channel, 256-position, nonvolatile memory,
digital potentiometer. With versatile programmability, the AD5142
allows multiple modes of operation, including read/write access
in the RDAC and EEMEM registers, increment/decrement of
resistance, resistance changes in ±6 dB scales, wiper setting read-
back, and extra EEMEM for storing user-defined information,
such as memory data for other components or a lookup table.
The AD5142 supports a dual-supply ±2.25 V to ±2.75 V operation
and a single-supply 2.3 V to 5.5 V operation, making the device
suitable for battery-powered applications and many other appli-
cations. In addition, the AD5142 uses a versatile SPI-compatible
serial interface, allowing speeds of up to 50 MHz. The EVA L-
AD5142DBZ can operate in single-supply or dual-supply mode
and incorporates an internal power supply from the USB.
Complete specifications for the AD5142 part can be found in the
AD5142 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-AD5142DBZ WITH MOTHERBOARD AND SDP-S
11008-001
Figure 1. Digital Picture of Evaluation Board with Low Voltage DigiPOT Motherboard and System Demonstration Platform

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TABLE OF CONTENTS
Features .............................................................................................. 1
Package Contents .............................................................................. 1
General Description ......................................................................... 1
E VA L-AD5142DBZ with Motherboard and SDP-S..................... 1
Revision History ............................................................................... 2
Evaluation Board Hardware ............................................................ 3
Power Supplies .............................................................................. 3
Test Circuits................................................................................... 4
Evaluation Board Software...............................................................8
Installing the Software ..................................................................8
Software Operation .................................................................... 10
Evaluation Board Schematics and Artwork................................ 11
Motherboard ............................................................................... 11
Daughter Board .......................................................................... 15
Ordering Information.................................................................... 18
Bill of Materials........................................................................... 18
REVISION HISTORY
11/12—Revision 0: Initial Version

Evaluation Board User Guide UG-471
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EVALUATION BOARD HARDWARE
POWER SUPPLIES
The EVAL-MB-LV-SDZ motherboard supports using single and
dual power supplies.
The E VA L -AD5142DBZ 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 VDD Analog positive power supply, VDD.
Single supply from 2.3 V to 5.5 V.
Dual supply from 2.25 V to 2.75 V.
J1-2 AGND Analog ground.
J1-3
VSS
Analog negative power supply, V
SS
.
Dual supply from −2.25 V to −2.75 V.
J2-1 VLOGIC Digital supply, from 1.8 V to VDD.
J2-2 DGND Digital ground.
Link Options
Several link and switch options are incorporated in the E VA L -
MB-LV-SDZ motherboard and should be set up before using
the board. Table 2 describes the positions of the links to control
the evaluation board via the SDP board using a PC. The
functions of these link options are described in detail in Table 3
through Table 6.
Table 2. Link Options Setup for SDP Control (Default)
Link No. Option
A5 +3V3
A11 3.3 V
A12 AGND
Linear Gain Setting Mode
The linear gain setting mode pin is controlled directly by
Jumper A1. If the jumper is placed in DEPEN, the AD5142
powers up in potentiometer mode, and the linear gain setting
mode can be controlled by software. If the jumper is placed in
INDEP, the part powers up in linear gain setting mode, loading
independent values for each resistor string—RAW1, RWB1, RAW2,
and RWB2. The part cannot be placed in potentiometer mode
again unless the jumper is manually placed in DEPEN.
Table 3. Link Functions
Link No.
Power Supply
Options
A5 VLOGIC This link selects one of the following as the digital supply:
+3V3 (3.3 V from SDP).
VLOGIC EXT (external supply from the J2 connector).
A11 VDD This link selects one of the following as the positive power supply:
+5 V (5 V from SDP).
3V3 (3.3 V from SDP).
VDD (external supply from the J1 connector).
A12
V
SS
This link selects one of the following as the negative power supply:
AGND.
EXTVSS (external supply from the J1 connector).

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TEST CIRCUITS
The E VA L -AD5142DBZ and E VA L -MB-LV-SDZ incorporate
several test circuits to evaluate the performance of the AD5142.
DAC
The digiPOT can be operated as a digital-to-analog converter
(DAC), as shown in Figure 2. Table 4 describes the options
available for the voltage references.
The output voltage is defined in Equation 1.
256
)( RDAC1 VVV
B
A
OUT
×−=
(1)
where:
RDAC1 is the code loaded in the RDAC1 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 and R35 external resistors, the user
can reduce the voltage of the voltage references. In this case, use
the A1 and B1 test points to measure the voltage applied to the
A and B terminals and to recalculate VAand VBin Equation 1.
Table 4. DAC Voltage References
Terminal
Link
Options
Description
A1 A9 AC+ Connects Terminal A1 to VDD/2
VDD Connects Terminal A1 to VDD
W1
BUF-W1
Connects Terminal W1 to an
output buffer
B1 A10 BIAS Connects Terminal B1 to VDD/2
VSS Connects Terminal B1 to VSS
AGND
Connects Terminal B1 to
analog ground
11008-002
VOUT1
R34
R35
A1
W1
RDAC1
A1
B1 W1
VDD
VDD
AC+
VDD
2
VDD
2
AGND
BIAS
B1
VSS
VSS
BUF-W1
Figure 2. DAC

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AC Signal Attenuation
The RDAC can be used to attenuate an ac signal, which must be
provided externally using the AC_INPUT connector, as shown
in Figure 3.
Depending on the voltage supply rails and the dc offset voltage
of the ac signal, various configurations can be used as described
in Table 5.
The signal attenuation is defined in Equation 2.







+
×=
AB
W
WB1
R
RR
nAttenuatio log
20)dB(
(2)
where:
RWis the wiper resistance.
RAB is the end-to-end resistance value.
RWB1 is the resistor between the W1 and B1 terminals.
Table 5. AC Signal Attenuation Link Options
Voltage
Supply
Maximum
AC Signal
Amplitude Link Options Conditions
Single VDD A9 AC+ No dc offset voltage;
the ac signal is
outside the voltage
supply rails due to
the dc offset voltage;
or the dc offset
voltage ≠ VDD/2.1
AC All other conditions.
A10 BIAS Use in conjunction
with the AC+ link.
GND All other conditions.
Dual VDD/VSS A9 AC+ The ac signal is
outside the voltage
supply rails due to
the dc offset voltage;
the dc offset
voltage ≠ 0 V.1
AC All other conditions.
A10 GND Use in conjunction
with the AC+ link.
VSS All other conditions.
1Recommended to ensure optimal total harmonic distortion (THD) performance.
11008-003
VOUT1
R34
R35
A1
W1
RDAC1
A1
B1 W1
AC
AC+
AGND
BIAS
B1
VSS
VSS
BUF-W1
AC_INPUT
1kHz
HPF
VDD
2
VDD
2
Figure 3. AC Signal Attenuator

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Signal Amplifier
The RDAC can be operated as an inverting or noninverting
signal amplifier supporting linear or pseudologarithmic gains.
Table 6 shows the available configurations.
The noninverting amplifier with linear gain is shown in Figure 4,
and the gain is defined in Equation 3.
AW2
WB2
R
R
G+
=1
(3)
where:
RWB2 is the code loaded for the RWB2 resistance.
RAW 2 is the code loaded for the RAW2 resistance.
11008-004
VOUT2
V
IN
RDAC2
R42
C1
10nF
W2
B2
A2 B2
W2
R41
1.7kΩ
A2
R43
Figure 4. Linear Noninverting Amplifier
R43 and R42 can be used to set the maximum and minimum
gain limits.
The noninverting amplifier with pseudologarithmic gain is
shown in Figure 5, and the gain is defined in Equation 4.
RDAC2
RDAC2
G− += 256 1
(4)
where:
RDAC2 is the code loaded in the RDAC2.
11008-005
VOUT2
V
IN
RDAC2
R42
C1
10nF
W2
B2
A2 B2
W2
R41
1.7kΩ
A2
R43
Figure 5. Pseudologarithmic Noninverting Amplifier
R43 and R42 can be used to set the maximum and minimum
gain limits.
The inverting amplifier with linear gain is shown in Figure 6,
and the gain is defined in Equation 5.
Note that the input signal, VIN, must be negative.
AW2
WB2
R
R
G−=
(5)
where:
RWB2 is the code loaded for the RWB2 resistance.
RAW 2 is the code loaded for the RAW2 resistance.
11008-006
VOUT2
VIN RDAC2
R42
C1
10nF
W2
B2
W2
A2 B2
R41
1.7kΩ
R43 A2
Figure 6. Linear Inverting Amplifier
R43 and R42 can be used to set the maximum and minimum
gain limits.
The inverting amplifier with pseudologarithmic gain is shown
in Figure 7, and the gain is defined in Equation 6.
2
256
2
RDAC
RDAC
G− −=
(6)
where:
RDAC2 is the code loaded in the RDAC2.
VOUT2
V
IN
RDAC2
R42
C1
10nF
W2
B2
A2 B2
W2
R41
1.7kΩ
A2
R43
11008-107
Figure 7. Pseudologarithmic Inverting Amplifier
R43 and R42 can be used to set the maximum and minimum
gain limits.

Evaluation Board User Guide UG-471
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Table 6. Amplifier Selection Link Options
Amplifier Gain
Linear Setting
Gain Mode Enabled Link Label
Noninverting Linear Yes A7 LIN
A6 N-INV
A8
N-INV
Pseudologarithmic No A7 LOG
A6
N-INV
A8 N-INV
Inverting Linear Yes A7 LIN
A6 INV
A8 INV
Pseudologarithmic No A7 LOG
A6
INV
A8 INV

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EVALUATION BOARD SOFTWARE
INSTALLING THE SOFTWARE
The E VA L -AD5142DBZ kit includes a CD containing the
evaluation board software. 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,
1. Start the Windows operating system and insert the CD into
the CD-ROM drive.
2. The installation software opens automatically. If it does not
open automatically, run the setup.exe file from the CD.
3. After the installation is complete, power up the evaluation
board as described in the Power Supplies section.
4. Connect the E VA L-AD5142DBZ and E VA L -MB-LV-SDZ
to the SDP board, and then connect the SDP board to the
PC using the USB cable included with the SDP board.
5. When the software detects the evaluation board, follow the
instructions that appear to finalize the installation.
To run the program, do the following:
1. Click Start > All Programs > Analog Devices > AD5142
> AD5142 Eval Board. To uninstall the program, click
Start > Control Panel > Add or Remove Programs >
AD5142 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 8). Simply connect the evaluation board to the USB
port of the PC, wait a few seconds, click Rescan, and follow
the instructions.
11008-007
Figure 8. Pop-Up Window Error
The main window of the E VA L -AD5142DBZ software then
opens, as shown in Figure 9.

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11008-022
11008-023
Figure 9. EVAL-AD5142DBZ Software Main Window

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SOFTWARE OPERATION
The main window of the E VA L -AD5142DBZ software has two
tabs, Visual Mode and Manual Control.
Visual Mode
The Visual Mode tab is divided into the following sections:
ALL CHANNELS COMMANDS, INDIVIDUAL CHANNEL
COMMANDS, and a block diagram that contains boxes for
changing the control register values and buttons and for controlling
the hardware pins.
The ALL CHANNELS COMMANDS section allows you to
send quick commands directly to the AD5142.
The INDIVIDUAL CHANNEL COMMANDS section allows
you to send quick commands to only specific channels of
the AD5142.
The block diagram allows you to update the control register
status. Each register value can be easily updated by changing the
value in its respective block within the diagram. In addition,
buttons are available that allow you to change the level of some
hardware pins.
Manual Mode
The Manual Mode tab, as shown in Figure 10, allows you to
customize an I2C data-word by manually switching the scroll
bars from 0 to 1 or from 1 to 0, as desired, and then clicking
SEND DATA.
11008-022
Figure 10. Manual Mode