Analog Devices EVAL-AD5161DBZ User manual

EVAL-AD5161DBZ User Guide
UG-624
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 AD5161 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 evaluation board used in conjunction with
low voltage digiPOT motherboard (EVAL-MB-LV-SDZ)
Multiple test circuits
Multiple ac/dc input signals
PC control via a separately purchased system demonstration
platform (SDP-B or SDP-S)
PC software for control
EVALUATION KIT CONTENTS
EVAL-AD5161DBZ evaluation 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 AD5161 data sheet
Electronic version of the EVAL-AD5161DBZuser guide
GENERAL DESCRIPTION
This user guide describes the evaluation boards for evaluating the
AD5161, a 256-position SPI-/I2C-selectable digital potentiometer.
The AD5161 supports single-supply 2.7 V to 5.5 V operation,
making the device suitable for battery-powered applications and
many applications requiring superior low temperature coefficient
performance.
In addition, the AD5161 has a pin-selectable SPI- or I2C-
compatible digital interface, which can be used to control the
wiper settings or to read back the wiper register content. In SPI
mode, the device can be daisy-chained (SDO to SDI), allowing
several parts to share the same control lines. In I2C mode,
Address Pin AD0 can be used to place up to two devices on the
same bus. In this same mode, command bits are available to reset
the wiper position to midscale or to shut down the device into a
state of zero power consumption.
The E VA L -AD5161DBZ daughter board and the E VA L -MB-
LV-SDZ motherboard can operate in single-supply mode and
incorporate an internal power supply from the USB.
Complete specifications for the AD5161 can be found in the
AD5161 data sheet, which is available from www.analog.com
and should be consulted in conjunction with this user guide
when using the evaluation board.
PHOTOGRAPH OF EVAL-AD5161DBZ WITH MOTHERBOARD AND SDP-B
11876-001
Figure 1. Digital Picture of Evaluation Board with Low Voltage DigiPOT Motherboard and System Demonstration Platform
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UG-624 EVAL-AD5161DBZ User Guide
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TABLE OF CONTENTS
Features .............................................................................................. 1
Evaluation Kit Contents................................................................... 1
General Description ......................................................................... 1
Photograph of EVAL-AD5161DBZ with Motherboard
and SDP-B.......................................................................................... 1
Revision History ............................................................................... 2
Evaluation Board Hardware ............................................................ 3
Power Supplies .............................................................................. 3
Link Options ................................................................................. 3
Digital Interface ............................................................................ 3
Test Circuits ...................................................................................4
Evaluation Board Software...............................................................6
Installing the Software ..................................................................6
Running the Software ...................................................................6
Operating the Software.................................................................7
Evaluation Board Schematics and Artwork...................................8
Motherboard ..................................................................................8
Daughter Board .......................................................................... 12
Bill of Materials............................................................................... 14
REVISION HISTORY
12/13—Revision 0: Initial Version
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EVAL-AD5161DBZ User Guide UG-624
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 and 0.1 µF
ceramic capacitors.
LINK OPTIONS
Several link and switch options are incorporated on the EVAL-
MB-LV-SDZ and E VA L -AD5161DBZ boards and must be set
up before using the evaluation system. The functions of these
link options are described in detail in Table 2 through Table 6.
By default, the evaluation system is set up to be controlled by a
PC via the SDP board.
DIGITAL INTERFACE
The E VA L -AD5161DBZ can be configured as an I2C or SPI
digital interface, depending on the position of the P9 jumper. If
the device is configured in I2C mode, the P10 jumper selects the
I2C address. See Table 3 for further details.
Table 1. Connector Functions
Voltage
Connector No. Label Description Min Max
J1-1 VDD Analog positive power supply, VDD 2.7 V 5.5 V
J1-2 AGND Analog ground
J2-1 VLOGIC Digital supply 2.7 V VDD
J2-2 DGND Digital ground
Table 2. Link Functions
Link No.
Power Supply
Options
Default Position
A5
V
LOGIC
Digital supply select options:
3.3 V
3.3 V (from the SDP board)
VLOGIC EXT (external supply from the J2 connector)
A11 VDD Positive power supply select options: 3.3 V
5 V (from the SDP board)
3.3 V (from the SDP board)
VDD (external supply from the J1 connector)
A12
GND
AGND
AGND
Table 3. Digital Interface Link Functions
Link No. Options Default Position
P9 Digital interface select options: SPI
SPI (use SPI digital interface).
I2C (use I2C digital interface).
P10 Chip select options (I2C mode only): Left
Left side: address pin is connected to AGND.
Right side: address pin is connected to VLOGIC.
This jumper is unused in SPI mode.
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UG-624 EVAL-AD5161DBZ User Guide
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TEST CIRCUITS
The E VA L -AD5161DBZ and E VA L -MB-LV-SDZ incorporate
several test circuits to evaluate the performance of the AD5161.
DAC
The RDAC can be operated as a digital-to-analog converter
(DAC), as shown in Figure 2.
VOUT1
R34
R35
A1
W1
RDAC
A
BW
VDD
VDD
AC+
VDD
2
VDD
2AGND
BIAS
B1
BUF-W1
11876-002
Figure 2. DAC
Table 5 shows the options available for the voltage references.
The output voltage is defined in Equation 1.
256
)( RDAC VVV B
A
OUT ×−=
(1)
where:
RDAC is the 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 and R35 external resistors, you 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 recalculate VAand VBin Equation 1.
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.
VOUT1
R34
R35
A1
W1
RDAC
A
BW
AC
AC+
AGND
BIAS
B1
BUF-W1
AC_INPUT
1kHz
HPF
V
DD
2
V
DD
2
11876-003
Figure 3. AC Signal Attenuator
Depending on the voltage supply rails and the dc offset voltage
of the ac signal, various configurations can be used, as described
in Table 4.
Table 4. AC Signal Attenuation Link Options
Link Options Conditions
A9 AC+ No dc offset voltage.
AC signal is outside the voltage supply rails
due to the dc offset voltage.
DC offset voltage ≠ VDD/2.1
AC All other conditions.
A10 BIAS Use in conjunction with AC+ link.1
AGND All other conditions.
1Recommended to ensure optimal total harmonic distortion (THD) performance.
The signal attenuation is defined in Equation 2.







+
×=
−− ENDTO
END
WWB
R
RR
nAttenuatio log20)dB(
(2)
where:
RWB is the resistance between the W and B terminals.
RWis the wiper resistance.
REND-TO-END is the end-to-end resistance value.
Table 5. DAC Voltage References
Link Settings
Terminal Daughter Board Motherboard Description
A1 P5: A1 position A9: AC+ position Connects Terminal A1 to VDD/2
A9: VDD position Connects Terminal A1 to VDD
W1 P6: W1 position BUF-W1: inserted Connects Terminal W1 to an output buffer
B1 P7: B1 position A10: BIAS position Connects Terminal B1 to VDD/2
A10: AGND position Connects Terminal B1 to analog ground
P8: inserted Closes the feedback loop of the second op amp in the AD8618
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EVAL-AD5161DBZ User Guide UG-624
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Signal Amplifier
The RDAC can be operated as an inverting or noninverting
signal amplifier and can support linear or pseudologarithmic
gain. 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.
R38
R
G
WB
+
=1
(3)
where RWB is the resistance between the W and B terminals.
VOUT2
V
IN
RDAC
R42
C1
10nF
W2
B2
W B
R41
1.7kΩ
R38
2.7kΩ
11876-004
Figure 4. Noninverting Amplifier with Linear Gain
The noninverting amplifier with pseudologarithmic gain is
shown in Figure 5, and the gain is defined in Equation 4.
AW
WB
R
R
G+=1
(4)
where:
RWB is the resistance between the W and B terminals.
RAW is the resistance between the A and W terminals.
VOUT2
V
IN
RDAC
R42
C1
10nF
W2
B2
A B
W
R41
1.7kΩ
A2
R43
11876-005
Figure 5. Noninverting Amplifier with Pseudologarithmic Gain
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.
R38
R
GWB −=
(5)
where RWB is the resistor between the W and B terminals.
Note that the input signal, VIN, must be negative.
11876-006
VOUT2
V
IN
RDAC
R42
C1
10nF
W2
B2
W B
R41
1.7kΩ
R38
2.7kΩ
NOTES
1. THE INPUT SIGNAL, V
IN
, MUST BE NEGATIVE.
Figure 6. Inverting Amplifier with Linear Gain
Table 6. Amplifier Selection Link Settings
Link Settings
Amplifier Gain Daughter Board Motherboard VIN Range
Noninverting Linear P5: A2 position, A7: LIN position, 0 V to VDD
P6: W2 position, A6: N-INV position,
P7: B2 position,
A8: N-INV position
P8: not inserted
Pseudologarithmic P5: A2 position, A7: LOG position, 0 V to VDD
P6: W2 position, A6: N-INV position,
P7: B2 position, A8: N-INV position
P8: not inserted
Inverting Linear P5: A2 position, A7: LIN position, −VDD to 0 V
P6: W2 position, A6: INV position,
P7: B2 position, A8: INV position
P8: not inserted
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UG-624 EVAL-AD5161DBZ User Guide
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EVALUATION BOARD SOFTWARE
INSTALLING THE SOFTWARE
The E VA L -AD5161DBZ kit includes evaluation board software
provided on a CD. The software is compatible with Windows® X P,
Windows Vista, and Windows 7 (both 32-bit and 64-bit versions).
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.
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 the installation is complete, power up the evaluation
board as described in the Power Supplies section.
4. Connect the E VA L -AD5161DBZ and E VA L -MB-LV-SDZ to
the SDP board and the SDP board to the PC.
5. When the software detects the evaluation board, follow the
instructions that appear to finalize the installation.
RUNNING THE SOFTWARE
To run the program, do the following:
1. Click Start > All Programs > Analog Devices > AD5161
> AD5161 Eval Board. (To uninstall the program, click
Start > Control Panel > Add or Remove Programs >
AD5161 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 7). If a connectivity error is displayed, connect the
evaluation board to the USB port of the PC and wait a few
seconds, and then click Rescan and follow the instructions
that appear on-screen.
11876-007
Figure 7. Pop-Up Window Error
The main window of the E VA L -AD5161DBZ software then
opens, as shown in Figure 8.
11876-008
Figure 8. EVAL-AD5161DBZ Software Main Window, Visual Control Tab
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EVAL-AD5161DBZ User Guide UG-624
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OPERATING THE SOFTWARE
The main window of the E VA L -AD5161DBZ software is
divided into two tabs: Visual Control and Manual Control.
Visual Control Tab
The Visual Control tab, as shown in Figure 8, contains a block
diagram that allows inputting data in hexadecimal format to be
written to or read from the device. To write data to the device, type
a hexadecimal value into the Data to write box and click Wr ite .
To read data from the device, click Read; the data is displayed
in hexadecimal format in the Data read box. A slider control,
located on the right side of the window, allows changing the
wiper setting.
Manual Control Tab
The Manual Control tab, as shown in Figure 9, allows customizing
an I2C or SPI data-word by manually switching each serial data-
word from 0 to 1 or from 1 to 0, as desired, and then clicking
I2C Write or SPI Write/Read. Similarly, data can also be read
from either I2C or SPI using the corresponding controls.
The I2C Data Written or SPI Data Written box shows the
value that is written to the evaluation board. It is set using the
sliders in the I2C – Wr ite or SPI – Write / Read section.
Exiting the window closes the program.
11876-009
Figure 9. EVAL-AD5161DBZ Software Main Window, Manual Control Tab
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UG-624 EVAL-AD5161DBZ User Guide
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EVALUATION BOARD SCHEMATICS AND ARTWORK
MOTHERBOARD
11876-010
Figure 10. SDP Connector and Power Supply
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EVAL-AD5161DBZ User Guide UG-624
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11876-011
Figure 11. Schematic of Test Circuits
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UG-624 EVAL-AD5161DBZ User Guide
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11876-012
Figure 12. Schematic of Connectors to Daughter Board
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