Dual 64-

and 256-Position I

C Nonvolatile

Memory Digital Potentiometers

AD5251/AD5252

Rev. 0

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However, no responsibility is assumed by Analog Devices for its use, nor for any
infringements of patents or other rights of third parties that may result from its use.
Specifications subject to change without notice. No license is granted by implication
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registered trademarks are the property of their respective owners.

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

www.analog.com

Fax: 781.326.8703

FEATURES

AD5251: Dual 64-position resolution
AD5252: Dual 256-position resolution
1 k, 10 k, 50 k, 100 k
Nonvolatile memory

stores wiper setting w/write protection

Power-on refreshed with EEMEM settings in 300 µs typ
EEMEM rewrite time = 540 µs typ
Resistance tolerance stored in nonvolatile memory
12 extra bytes in EEMEM for user-defined information
I

C compatible serial interface

Direct read/write access of RDAC

and EEMEM registers

Predefined linear increment/decrement commands
Predefined ±6 dB step change commands
Synchronous or aysynchronous dual channel update
Wiper setting read back
4 MHz bandwidth--1 k version
Single supply 2.7 V to 5.5 V
Dual supply ±2.25 V to ±2.75 V
2 slave address decoding bits allow operation of 4 devices
100-year typical data retention T

= 55°C

Operating temperature 40°C to +85°C

APPLICATIONS

Mechanical potentiometer replacement
General purpose DAC replacement
LCD panel V

COM

adjustment

White LED brightness adjustment
RF base station power amp bias control
Programmable gain and offset control
Programmable voltage-to-current conversion
Programmable power supply
Sensor calibrations

FUNDAMENTAL BLOCK DIAGRAM

RDAC1
REGIS-

TER

RDAC3
REGIS-

TER

RDAC1

RDAC3

DATA

CONTROL

COMMAND

DECODE LOGIC

ADDRESS

DECODE LOGIC

CONTROL LOGIC

AD5251/

AD5252

SERIAL

INTERFACE

POWER-

ON RESET

DGND

SCL

SDA

AD0
AD1

RDAC EEMEM

RAB

TOL

03823-0-001

EEMEM

POWER-ON

REFRESH

Figure 1.

The terms nonvolatile memory and EEMEM are used interchangeably.

The terms digital potentiometer and RDAC are used interchangeably.

GENERAL DESCRIPTION

The AD5251/AD5252 are dual-channel, I

C, nonvolatile mem-

ory, digitally controlled potentiometers with 64/256 positions,
respectively. These devices perform the same electronic adjust-
ment functions as mechanical potentiometers, trimmers, and
variable resistors. The parts' versatile programmability 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
readback, and extra EEMEM for storing user-defined infor-
mation such as memory data for other components, look-up
table, or system identification information.

The AD5251/AD5252 allow the host I

C controllers to write

any of the 64- or 256-step wiper settings in the RDAC registers
and store them in the EEMEM. Once the settings are stored,

they are restored automatically to the RDAC registers at system
power-on; the settings can also be restored dynamically.

The AD5251/AD5252 provide additional increment,
decrement, +6 dB step change, and 6 dB step change in
synchronous or asynchronous channel update modes. The
increment and decrement functions allow stepwise linear
adjustments, while ±6 dB step changes are equivalent to
doubling or halving the RDAC wiper setting. These functions
are useful for steep-slope nonlinear adjustments such as white
LED brightness and audio volume control. The parts have a
patented resistance tolerance storing function which enable the
user to access the EEMEM and obtain the absolute end-to-end
resistance values of the RDACs for precision applications.

The AD5251/AD5252 are available in TSSOP-14 packages in
1 k, 10 k, 50 k, and 100 k options and all parts can
operate over the 40°C to +85°C extended industrial
temperature range.

AD5251/AD5252

Rev.0 | Page 2 of 28

TABLE OF CONTENTS

Electrical Characteristics ................................................................. 3

Interface Timing Characteristics................................................ 7

Absolute Maximum Ratings............................................................ 8

ESD Caution.................................................................................. 8

Pin Configuration and Function Description .............................. 9

C Interface Timing Diagram.................................................... 9

C Interface General Description................................................ 10

C Interface Detail Description ................................................... 11

RDAC/EEMEM Write ............................................................... 11

C Compatible 2-Wire Serial Bus................................................ 15

Typical Performance Characteristics ........................................... 16

Operational Overview.................................................................... 20

Linear Increment and Decrement Commands ...................... 20

±6 dB Adjustments (Doubling/Halving WIPER Setting) ..... 20

Digital Input/Output Configuration........................................ 21

Multiple Devices on One Bus ................................................... 21

Terminal Voltage Operation Range ......................................... 21

Power-Up and Power-Down Sequences.................................. 21

Layout and Power Supply Biasing ............................................ 22

Digital Potentiometer Operation ............................................. 22

Programmable Rheostat Operation......................................... 22

Programmable Potentiometer Operation ............................... 23

Applications..................................................................................... 24

LCD Panel V

com

Adjustment ..................................................... 24

Current-Sensing Amplifier ....................................................... 24

Adjustable High Power LED Driver ........................................ 24

Outline Dimensions ....................................................................... 25

Ordering Guide .......................................................................... 25

REVISION HISTORY

6/04--Revision 0: Initial Version

AD5251/AD5252

Rev. 0 | Page 3 of 28

ELECTRICAL CHARACTERISTICS

1 k Version. V

= 3 V ± 10% or 5 V ± 10%; V

= 0 V or V

= ± 2.5 V ± 10%; V

= +V

, V

= 0 V, 40°C < T

< +85°C, unless

otherwise noted.
Table 1.

Parameter

Symbol

Conditions

Min

Typ

Max

Unit

DC CHARACTERISTICS
RHEOSTAT MODE

Resolution N

AD5251/AD5252

6/8

Bits

Resistor Differential
Nonlinearity

R-DNL R

, R

= NC, V

= 5.5 V, AD5251

0.5

±0.2

+0.5

LSB

, R

= NC, V

= 5.5 V, AD5252

±0.25

LSB

, R

= NC, V

= 2.7 V, AD5251

0.75

±0.3

+0.75

LSB

, R

= NC, V

= 2.7 V, AD5252

1.5

±0.3

+1.5

LSB

Resistor Nonlinearity

R-INL

, R

= NC, V

= 5.5 V, AD5251

0.5

±0.2

+0.5

LSB

, R

= NC, V

= 5.5 V, AD5252

±0.5

LSB

, R

= NC, V

= 2.7 V, AD5251

+2.5

LSB

, R

= NC, V

= 2.7 V, AD5252

+14

LSB

Nominal Resistor Tolerance

= 25°C

+30

Resistance Temperature
Coefficent

) × 10

650

ppm/°C

Wiper Resistance

= 1 V/R, V

= 5 V

130

= 1 V/R, V

= 3 V

200

300

Channel Resistance Matching

AB1

AB3

0.15

DC CHARACTERISTIC
POTENTIOMETER DIVIDER MODE

Differential Nonlinearity

DNL

AD5251

0.5 ±0.1 +0.5 LSB

AD5252

±0.25

LSB

Integral Nonlinearity

INL

AD5251

0.5 ±0.2 +0.5 LSB

AD5252

±0.5

LSB

Voltage Divider Temperature
Coefficent

) × 10

Code = half scale

ppm/°C

Full-Scale Error

WFSE

Code = full scale, V

= 5.5 V, AD5251

LSB

Code = full scale, V

= 5.5 V, AD5252

LSB

Code = full scale, V

= 2.7 V, AD5251

-6

4 0 LSB

Code = full scale, V

= 2.7 V, AD5252

LSB

Zero-Scale Error

WZSE

Code = zero scale, V

= 5.5 V, AD5251

LSB

Code = zero scale, V

= 5.5 V, AD5252

LSB

Code = zero scale, V

= 2.7 V, AD5251

LSB

Code = zero scale, V

= 2.7 V, AD5252

LSB

RESISTOR

TERMINALS

Voltage Range

, V

Capacitance

Ax, Bx

, C

f = 1 kHz, measured to GND,
Code = half scale

Capacitance

f = 1 kHz, measured to GND,
Code = half scale

Common-Mode Leakage

Current I

= V

0.01

µA

DIGITAL INPUTS and OUTPUTS

Input Logic High

= 5 V, V

= 0 V

2.4

= 2.7 V/0 V or V

= ± 2.5 V

2.1

Input Logic Low

= 5V, V

= 0 V

0.8

Output Logic High (SDA)

PULL-UP

= 2.2 k to V

= 5 V, V

= 0 V

4.9

Output Logic Low (SDA)

PULL-UP

= 2.2 k to V

=5 V, V

= 0 V

0.4

AD5251/AD5252

Rev. 0 | Page 4 of 28

Parameter

Symbol

Conditions

Min

Typ

Max

Unit

Leakage Current

WP = V

µA

A0 Leakage Current

A0 = GND

µA

Input Leakage Current (Other
than WP and A0)

= 0 V or V

±1

µA

Input Capacitance

POWER

SUPPLIES

Single-Supply Power Range

= 0 V

2.7

5.5

Dual-Supply Power Range

±2.25

±2.75

Positive Supply Current

= V

or V

= GND

µA

Negative Supply Current

= V

or V

= GND, V

= +2.5 V,

= 2.5 V

µA

EEMEM Data Storing Mode
Current

DD_STORE

= V

or V

= GND

EEMEM Data Restoring Mode
Current

DD_RESTORE

= V

or V

= GND

2.5

Power Dissipation

DISS

= V

= 5 V or V

= GND

0.075

Power Supply Sensitivity

PSS

= 5 V ± 10%

-0.025

0.01

0.025

%/%

= 3 V ± 10%

0.04

0.02

0.04

%/%

DYNAMIC CHARACTERISTICS

5, 8

Bandwidth 3 dB

= 1 k

MHz

Total Harmonic Distortion

THD

= 1 V rms, V

= 0 V, f = 1 kHz

0.05

Settling Time

= V

, V

= 0 V

0.2

µs

Resistor Noise Voltage

N_WB

= 500 , f = 1 kHz (thermal noise only)

nV/Hz

Digital Crosstalk

= V

, V

= 0 V, measure V

with

adjacent RDAC making full-scale change

Analog Coupling

Signal input at A1 and measure the
output at W3, f = 1 kHz

Typical represents the average reading at 25°C and V

= 5 V.

Resistor position nonlinearity error (R-INL) is the deviation from an ideal value measured between the maximum resistance and the minimum resistance wiper

positions. R-DNL measures the relative step change from ideal between successive tap positions. Parts are guaranteed monotonic, except R-DNL of AD5252

1 k

version at V

= 2.7 V, I

= V

/R for both V

= 3 V or V

= 5 V.

INL and DNL are measured at V

with the RDAC configured as a potentiometer divider similar to a voltage output D/A converter. V

= V

and V

= 0 V. DNL

specification limits of ±1 LSB maximum are guaranteed monotonic operating conditions.

Resistor Terminals A, B, and W have no limitations on polarity with respect to each other.

Guaranteed by design and not subject to production test.

cmd 0 NOP should be activated after cmd 1 to minimize I

DD_READ

current consumption.

DISS

is calculated from I

× V

= 5 V.

All dynamic characteristics use V

= 5 V.

AD5251/AD5252

Rev. 0 | Page 5 of 28

10 k, 50 k, 100 k Versions. V

= +3 V ± 10% or + 5 V ± 10%. V

= 0 V or V

= ± 2.5 V ± 10%. V

= +V

, V

= 0 V,

40°C < T

< +85°C, unless otherwise noted.

Table 2.

Parameter

Symbol

Conditions

Min

Typ

Max

Unit

CHARACTERISTICS

RHEOSTAT

MODE

Resolution N

AD5251/AD5252

6/8

Bits

Resistor Differential NL

R-DNL R

, R

= NC, AD5251

-0.75

±0.1

+0.75

LSB

, R

= NC, AD5252

-1

±0.25

LSB

Resistor Nonlinearity

R-INL

, R

= NC, AD5251

-0.75

±0.25

+0.75

LSB

, R

= NC, AD5252

-2.5

±1

+2.5

LSB

Nominal Resistor Tolerance

= 25°C

-20

+20

Resistance Temperature
Coefficent

) × 10

650 ppm/°C

Wiper Resistance

= 1 V/R, V

= 5 V

130

= 1 V/R, V

= 3 V

200

300

Channel Resistance Matching

AB1

AB2

= 10 k, 50 k

0.15

= 100 k

0.05

DC CHARACTERISTICS
POTENTIOMETER DIVIDER
MODE

Differential Nonlinearity

DNL

AD5251

-0.5 ±0.1

+0.5 LSB

AD5252

-1 ±0.3 +1 LSB

Integral Nonlinearity

INL

AD5251

-0.5 ±0.15 +0.5 LSB

AD5252

-1.5 ±0.5

+1.5 LSB

Voltage Divider

Temperature Coefficent

) × 10

Code = half scale

ppm/°C

Full-Scale Error

WFSE

Code = full scale, AD5251

-1

-0.3

LSB

Code = full scale, AD5252

-3

-1

LSB

Zero-Scale Error

WZSE

Code = zero scale, AD5251

0.3

LSB

Code = zero scale, AD5252

1.2

LSB

RESISTOR

TERMINALS

Voltage Range

, V

Capacitance

Ax, Bx

, C

f = 1 kHz, measured to GND,
Code = half scale

85 pF

Capacitance

f = 1 kHz, measured to GND,
Code = half scale

95 pF

Common-Mode Leakage
Current

= V

0.01

µA

DIGITAL INPUTS and OUTPUTS

Input Logic High

=5 V, V

= 0 V

2.4

= +2.7 V/0 V or V

= ±2.5 V

2.1

Input Logic Low

= 5 V, V

= 0 V

0.8

= +2.7 V/0 V or V

=±2.5 V

0.6

Output Logic High (SDA)

PULL-UP

= 2.2 k to V

= 5 V, V

= 0 V

4.9

Output Logic Low (SDA)

PULL-UP

= 2.2 k to V

= 5 V, V

= 0 V

0.4

Leakage Current

WP = V

µA

A0 Leakage Current

A0 = GND

µA

Input Leakage Current

(Other than WP and A0)

= 0 V or V

±1

µA

Input Capacitance

5 pF

POWER

SUPPLIES

Single-Supply Power Range

= 0 V

2.7

5.5

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