ANALOG DEVICES UG-243 Service Manual

Evaluation Board User Guide

UG-243

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 AD5172 Digital Potentiometer

FEATURES

Full-featured evaluation board for the AD5172
Various test circuits
Various ac/dc input signals
PC control via a separately purchased system development

platform (SDP)
PC software for control
Resistor tolerance error stored in EEMEM

PACKAGE CONTENTS

EVAL-AD5172SDZ board
CD that includes

Self-installing software that allows users to control the

board and exercise all functions of the device
Electronic version of the AD5172 data sheet
Electronic version of the UG-243 user guide

GENERAL DESCRIPTION

This user guide describes the evaluation board for evaluating the
AD5172, a dual-channel, 256-position, one-time programmable
(OTP) memory digital potentiometer that employ fuse link
technology to achieve memory retention of resistance settings.

The on-board socket allows the user to easily replace the device
for reprogramming of the OTP memory.

The AD5172 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 AD5172 uses a versatile I
operates in fast mode, allowing speeds of up to 400 kHz.

The EVAL-AD5172SDZ can operate in single-supply mode and
incorporates an internal power supply from the USB.

Complete specifications for the AD5172 part can be found in
the AD5172 data sheet, which is available from Analog Devices,
Inc., and should be consulted in conjunction with this user
guide when using the evaluation board.

2

C serial interface that

DIGITAL PICTURE OF EVALUATION BOARD WITH SYSTEM DEVELOPMENT PLATFORM

SYSTEM DEVELOPMENT

PLATFO RM

EVAL-AD5172S DZ

09610-001

Figure 1.

PLEASE SEE THE LAST PAGE FOR AN IMPORTANT
WARNING AND LEGAL TERMS AND CONDITIONS.

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UG-243 Evaluation Board User Guide

TABLE OF CONTENTS

Features.............................................................................................. 1

Package Contents.............................................................................. 1

General Description ......................................................................... 1

Digital Picture of Evaluation Board with System Development

Platform ............................................................................................. 1

Revision History ............................................................................... 2

Evaluation Board Hardware............................................................ 3

Power Supplies ..............................................................................3

Link Options ................................................................................. 3

REVISION HISTORY

1/11—Revision 0: Initial Version



Test Circuits ...................................................................................4

Evaluation Board Software...............................................................6

Installing the Software..................................................................6

Running the Software ...................................................................6

Software Operation.......................................................................7

Evaluation Board Schematics and Artwork...................................8

Ordering Information.................................................................... 14

Bill of Materials........................................................................... 14

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Evaluation Board User Guide UG-243

EVALUATION BOARD HARDWARE

POWER SUPPLIES

The EVAL-AD5172SDZ supports using single power supplies.

The evaluation board can be powered either from the SDP port
or externally by the J1-1 and J1-2 connectors, as described in
Tabl e 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 Analog positive power supply, VDD.
VDD

J1-2 GND Analog ground.

Table 3. Link Functions

Link No. Power Supply Options

A25 VDD This link selects one of the following as the positive power supply:
5 V (from SDP).

3.3 V (from SDP).
EXT (external supply from the J1-1 connector).
A24 VSS This link should be connected to GND (analog ground).

For single-supply operation, it is 2.7 V
to 5 V.

LINK OPTIONS

Several link and switch options are incorporated in the
evaluation board and should be set up before using the board.
Tabl e 2 describes the positions of the links to control the
evaluation board by a PC, via the SDP board, using the EVAL­AD5172SDZ in single-supply mode. The functions of these link
options are described in detail in Tab l e 3 through Table 6.

Table 2. Link Options Setup for SDP Control (Default)

Link No. Option
A25 3.3 V
A24 GND

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UG-243 Evaluation Board User Guide

A

V

V

TEST CIRCUITS

The EVAL-AD5172SDZ incorporates several test circuits to
evaluate the AD5172 performance.

DAC

RDAC1 can be operated as a digital-to-analog converter (DAC),
as shown in Figure 2.

– V

2

– V

2

AC + DC

SS

VDD

V

DD

RDAC1

DC

SS

GND

A1

R34

W1

R35

W1

BUF_W1

B1

W1_BUF

09610-002

A1

B1

Figure 2. DAC

Connects Terminal A1 to

− VSS)/2

(V

DD

Connects Terminal W1 to an
output buffer

Connects Terminal B1 to

− VSS)/2

(V

DD

Connects Terminal B1 to
analog ground

R

WB1

VVV ×−=

)(

B1

A1

(1)

256

and VB0 in Equation 1.

A0

V

DD

V

DD

Tabl e 4 shows the options available for the voltage references.

Table 4. DAC Voltage References

Terminal Link Options Description

A1 A20 AC + DC

VDD Connects Terminal A1 to VDD
W1 BUF_W1

B1 A21 DC

GND

The output voltage is defined in Equation 1.

OUT

where:

R

is the resistor between the W1 and B1 terminals.

WB1

V

is the voltage applied to the A1 terminal (A20 link).

A1

V

is the voltage applied to the B1 terminal (A21 link)

B1

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
A0 and B0 terminals and recalculate V

AC Signal Attenuation

RDAC1 can be used to attenuate an ac signal, which must be
provided externally using the AC_INPUT connector, as shown
in Figure 3.

–

DD

SS

2

C_INPUT

1µF

V

DD

– V

2

SS

AC + DC

AC

RDAC1

DC

GND

A1

R34

W1

R35

W1

BUF_W1

R36

B1

W1_BUF

A1

B1

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 Tabl e 5 .

Table 5. AC Signal Attenuation Link Options

Link Options Conditions

A20 AC + DC No dc offset voltage.

AC signal is outside the voltage supply rails

due to the dc offset voltage.
DC offset voltage ≠ VDD/21.
AC All other conditions.
A21 DC Use in conjunction with ac + dc link.
GND All other conditions.

1

Recommended to ensure optimal total harmonic distortion (THD) performance.

The signal attenuation is defined in Equation 2.

⎛
⎜

nAttenuatio log20)dB( (2)

×=

⎜

R

⎝

⎞

+

RR

WWB1

⎟
⎟

−− ENDTOEND

⎠

where:

is the resistor between the W1 and B1 terminals.

R

WB1

is the wiper resistance.

R

W

R

END-TO-END

is the end-to-end resistance value.

In addition, R36 can be used to achieve a pseudologarithmic
attenuation. To do so, adjust the R36 resistor until a desirable
transfer function is found.

09610-003

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Evaluation Board User Guide UG-243

Signal Amplifier

RDAC2 can be operated as an inverting or noninverting signal
amplifier supporting linear or pseudo logarithmic 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.

R

WB2

(3)

R38

is the resistor between the W2 and B2 terminals.

R41

R38

2.7kΩ

W2

W2

1.7kΩ

RDAC2

V

OUT

C1

OAVOUT

10nF

B2

R42

B2

09610-004

V

IN

where

G

1

R

WB2

Figure 4. Linear Noninverting Amplifier

The noninverting amplifier with pseudologarithmic gain is
shown in Figure 5, and the gain is defined in Equation 4.

R

G 1 (4)

WB2

R

AW2

where:

is the resistor between the W2 and B2 terminals.

R

WB2

is the resistor between the A2 and W2 terminals.

R

AW 2

R41

V

R43

1.7kΩ

IN

W2

A2

W2

RDAC2

10nF

B2

B2A2

C1

R42

V

OUT

OAVOUT

09610-005

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, V

R

WB2

(5)



G

R38

where R

is the resistor between the W2 and B2 terminals.

WB2

R38

2.7kΩ

V

IN

W2

W2

Figure 6. Linear Inverting Amplifier

, must be negative.

IN

R41

1.7kΩ

B2

RDAC2

V

OUT

C1

OAVOUT

10nF

B2

R42

09610-006

Table 6. Amplifier Selection Link Options

Amplifier Gain Link Label V

Range

IN

Noninverting Linear A27 LINEAR 0 V to VDD
A29 NON-INV
A30 NON-INV
Pseudo logarithmic A27 PSEUDOLOG 0 V to VDD
A29 NON-INV
A30 NON-INV
Inverting Linear A27 LINEAR −VDD to 0 V
A29 INV
A30 INV

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