Analog Devices EVAL-AD5142DBZ Manuale utente

Evaluation Board User Guide

UG-471

One Technology Way •P. O. Box 9106 •Norwood, MA 02062-9106, U.S.A. •Tel: 781.329.4700 •Fax: 781.461.3113 •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

UG-471 Evaluation Board User Guide

Rev. 0 | Page 2 of 20

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

Rev. 0 | Page 3 of 20

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

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

This link selects one of the following as the negative power supply:

AGND.

EXTVSS (external supply from the J1 connector).

UG-471 Evaluation Board User Guide

Rev. 0 | Page 4 of 20

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

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

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

RDAC1

B1 W1

VDD

AC+

VDD

AGND

BIAS

VSS

BUF-W1

Figure 2. DAC

Evaluation Board User Guide UG-471

Rev. 0 | Page 5 of 20

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.











+

×=

WB1

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

RDAC1

B1 W1

AC+

AGND

BIAS

VSS

BUF-W1

AC_INPUT

1kHz

HPF

VDD

Figure 3. AC Signal Attenuator

UG-471 Evaluation Board User Guide

Rev. 0 | Page 6 of 20

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

G+

(3)

where:

RWB2 is the code loaded for the RWB2 resistance.

RAW 2 is the code loaded for the RAW2 resistance.

11008-004

VOUT2

RDAC2

R42

10nF

A2 B2

R41

1.7kΩ

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

G−

+= 256

(4)

where:

RDAC2 is the code loaded in the RDAC2.

11008-005

VOUT2

RDAC2

R42

10nF

A2 B2

R41

1.7kΩ

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

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

10nF

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.

256

RDAC

G−

−=

(6)

where:

RDAC2 is the code loaded in the RDAC2.

VOUT2

RDAC2

R42

10nF

A2 B2

R41

1.7kΩ

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

Rev. 0 | Page 7 of 20

Table 6. Amplifier Selection Link Options

Amplifier Gain

Linear Setting

Gain Mode Enabled Link Label

Noninverting Linear Yes A7 LIN

A6 N-INV

N-INV

Pseudologarithmic No A7 LOG

N-INV

A8 N-INV

Inverting Linear Yes A7 LIN

A6 INV

A8 INV

Pseudologarithmic No A7 LOG

INV

A8 INV

UG-471 Evaluation Board User Guide

Rev. 0 | Page 8 of 20

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.

Evaluation Board User Guide UG-471

Rev. 0 | Page 9 of 20

11008-022

11008-023

Figure 9. EVAL-AD5142DBZ Software Main Window

UG-471 Evaluation Board User Guide

Rev. 0 | Page 10 of 20

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

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