Analog Devices AD5228 Datasheet

32-Position Manual Up/Down Control

FEATURES

32-position digital potentiometer
10 kΩ, 50 kΩ, 100 kΩ end-to-end terminal resistance
Simple manual up/down control
Self-contained, requires only 2 pushbutton tactile switches
Built-in adaptive debouncer
Discrete step-up/step-down control
Autoscan up/down control with 4 steps per second
Pin-selectable zero-scale/midscale preset
Low potentiometer mode tempco, 5 ppm/°C
Low rheostat mode tempco, 35 ppm/°C
Digital control compatible
Ultralow power, I
Low operating voltage, 2.7 V to 5.5 V
Automotive temperature range, −40°C to +105°C
Compact thin SOT-23-8 (2.9 mm × 3 mm) Pb-free package

APPLICATIONS

Mechanical potentiometer and trimmer replacements
LCD backlight, contrast, and brightness controls
Digital volume control
Portable device-level adjustments
Electronic front panel-level controls
Programmable power supply

GENERAL DESCRIPTION

The AD5228 is Analog Devices’ latest 32-step-up/step-down
control digital potentiometer emulating mechanical potenti­ometer operation
manual control with just two external pushbutton tactile
switches. The AD5228 is designed with a built-in adaptive
debouncer that ignores invalid bounces due to contact bounce
commonly found in mechanical switches. The debouncer is
adaptive, accommodating a variety of pushbutton tactile
switches that generally have less than 10 ms of bounce time
during contact closures. When choosing the switch, the user
should consult the timing specification of the switch to ensure
its suitability in an AD5228 application.

1

The term s digital potentiometer and RDAC are used interchangeably.

= 0.4 µA typ and 3 µA max

DD

1

. Its simple up/down control interface allows

Potentiometer

AD5228

FUNCTIONAL BLOCK DIAGRAM

D

UP/DOWN
CONTROL

LOGIC

DISCRETE

STEP/AUTO

SCAN DETECT

ADAPTIVE

DEBOUNCER

Figure 1.

PUSH-UP

BUTTON

PUSH-DOWN

BUTTON

V

DD

R1 R2

PU

PD

The AD5228 can increment or decrement the resistance in
discrete steps or in autoscan mode. When the

is pressed briefly (no longer than 0.6 s), the resistance of the
AD5228 changes by one step. When the

PU

continuously for more than a second, the device activates the
autoscan mode and changes four resistance steps per second.

The AD5228 can also be controlled digitally; its up/down
features simplify microcontroller usage. The AD5228 is available
in a compact thin SOT-23-8 (TSOT-8) package. The part is
guaranteed to operate over the automotive temperature range of

−40°C to +105°C.

The AD5228’s simple interface, small footprint, and very low
cost enable it to replace mechanical potentiometers and
trimmers with typically 3× improved resolution, solid-state
reliability, and faster adjustment, resulting in considerable cost
saving in end users’ systems.

Users who consider EEMEM potentiometers should refer to the
recommendations in the Applications section.

Table 1. Truth Table

PU

Operation1

PD

0 0 RWB Decrement
0 1 RWB Increment
1 0 RWB Decrement
1 1 RWB Does Not Change

1

RWA increments if RWB decrements and vice versa.

AD5228

E
C
O
D
E

ZERO- OR MID-

SCALE PRESET

PRE GND

or PD button

PU

A

W

B

or PD button is held

04422-0-001

Rev. 0

Information furnished by Analog Devices is believed to be accurate and reliable.
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
or otherwise under any patent or patent rights of Analog Devices. Trademarks and
registered trademarks are the property of their respective owners.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] www.analog.com
Fax: [phone] © 2004 Analog Devices, Inc. All rights reserved.

AD5228

TABLE OF CONTENTS

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

Power-Up and Power-Down Sequences.................................. 14

Interface Timing Diagrams ......................................................... 4

Absolute Maximum Ratings............................................................ 5

ESD Caution.................................................................................. 5

Pin Configuration and Function Descriptions............................. 6

Typical Performance Characteristics ............................................. 7

Theory of Operation ...................................................................... 11

Programming the Digital Potentiometers............................... 12

Controlling Inputs ...................................................................... 13

Terminal Voltage Operation Range.......................................... 13

REVISION HISTORY

Revision 0: Initial Version

Layout and Power Supply Biasing............................................ 14

Applications..................................................................................... 15

Manual Adjustable LED Driver................................................ 15

Adjustable Current Source for LED Driver ............................ 15

Automatic LCD Panel Backlight Control................................ 16

Audio Amplifier with Volume Control ................................... 16

Constant Bias with Supply to Retain Resistance Setting...... 17

Outline Dimensions....................................................................... 18

Ordering Guide .......................................................................... 18

Rev. 0 | Page 2 of 20

AD5228

ELECTRICAL CHARACTERISTICS

10 kΩ, 50 kΩ, 100 kΩ versions: VDD = 3 V ± 10% or 5 V ± 10%, VA = VDD, VB = 0 V, −40°C < TA < +105°C, unless otherwise noted.

Table 2.

Parameter Symbol Conditions Min Typ1 Max Unit

DC CHARACTERISTICS, RHEOSTAT MODE

Resistor Differential Nonlinearity2 R-DNL RWB, A terminal = no connect −0.5 ±0.05 +0.5 LSB

Resistor Integral Nonlinearity2 R-INL RWB, A terminal = no connect −0.5 ±0.1 +0.5 LSB

Nominal Resistor Tolerance3 ∆RAB/RAB −20 +20 %

Resistance Temperature Coefficient (∆RAB/RAB) × 104/∆T 35 ppm/°C

Wiper Resistance RW V

V

DC CHARACTERISTICS, POTENTIOMETER DIVIDER MODE
(Specifications apply to all RDACs)

Resolution N 5 Bits

Integral Nonlinearity3 INL −0.5 ±0.05 +0.5 LSB

Differential Nonlinearity

3, 5

DNL −0.5 ±0.05 +0.5 LSB

Voltage Divider Temperature Coefficient (∆VW/VW) × 104/∆T Midscale 5 ppm/°C

Full-Scale Error V

Zero-Scale Error V

≥+15 steps from midscale −1 −0.5 0 LSB

WFSE

≤−16 steps from midscale 0 0.3 0.5 LSB

WZSE

RESISTOR TERMINALS

Voltage Range6 V

Capacitance4 A, B C

With respect to GND 0 VDD V

A, B, W

f = 1 MHz, measured to GND 140 pF

A, B

Capacitance4 W CW f = 1 MHz, measured to GND 150 pF

Common-Mode Leakage ICM V

PU, PD INPUTS

Input High VIH VDD = 5 V 2.4 5.5 V

Input Low VIL VDD = 5 V 0 0.8 V

Input Current II V

Input Capacitance4 C

5 pF

I

POWER SUPPLIES

Power Supply Range VDD

Supply Standby Current I

Supply Active Current7 I

Power Dissipation

7, 8

P

0.4 3 µA

DD_STBY

DD_ACT

V

DISS

Power Supply Sensitivity PSSR VDD = 5 V ± 10% 0.01 0.05 %/%

Footnotes on next page.

= 2.7 V 100 200 Ω

DD

= 5.5 V 50 Ω

DD

= VB = VW 1 nA

A

= 0 V or 5 V ±1 µA

IN

= 5 V, PU = PD = VDD

V

DD

= 5 V, PU or PD = 0 V

V

DD

= 5 V 17 µW

DD

2.7 5.5 V

50 110 µA

Rev. 0 | Page 3 of 20

AD5228

Parameter Symbol Conditions Min Typ1 Max Unit

DD_STBY

4, 9, 10, 11

6 ms

DB

t

12 ms

PU

t

12 ms

PD

t

1 µs

PU_REP

t

1 µs

PD_REP

0.6 0.8 1.2 s

0.16 0.25 0.38 s

0.05 %

nV/√Hz

× VDD only. I

AS_START

R

N_WB

= VDD/100 kΩ + I

DD_ACT

duration should be short. Users should not hold PU or PD pin to ground longer than necessary to elevate power

DD_ACT

(internal oscillator operating current) when PU or PD is connected to ground.

OSC

or PD = 0 V

PU

or PD = 0 V

PU

= 1 V rms, RAB = 10 kΩ,

V

A

V

= 0 V dc, f = 1 kHz

B

= 5 kΩ, f = 1 kHz 14

WB

, the AD5528 increments again, see Figure 7. Similar

AS_START

DYNAMIC CHARACTERISTICS

Built-in Debounce and Settling Time 12 t

PU Low Pulse Width

PD Low Pulse Width

PU High Repetitive Pulse Width

PD High Repetitive Pulse Width

Autoscan Start Time t

Autoscan Time tAS

Bandwidth –3 dB BW_10 RAB = 10 kΩ, midscale 460 kHz

BW_50 RAB = 50 kΩ, midscale 100 kHz

BW_100 RAB = 100 kΩ, midscale 50 kHz

Total Harmonic Distortion THD

Resistor Noise Voltage e

1

Typicals represent average readings at 25°C, VDD = 5 V.

2

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.

3

INL and DNL are measured at VW with the RDAC configured as a potentiometer divider similar to a voltage output D/A converter. VA = VDD and VB = 0 V.

4

Guaranteed by design and not subject to production test.

5

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

6

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

7

PU and PD have 100 kΩ internal pull-up resistors, I

8

P

is calculated based on I

DISS

dissipation.

9

Bandwidth, noise, and settling time are dependent on the terminal resistance value chosen. The lowest R value results in the fastest settling time and highest

bandwidth. The highest R value results in the minimum overall power consumption.

10

All dynamic characteristics use VDD = 5 V.

11

Note that all input control voltages are specified with tR = tF = 1 ns (10% to 90% of VDD) and timed from a voltage level of 1.6 V. Switching characteristics are measured
using VDD = 5 V.

12

The debouncer keeps monitoring the logic-low level once PU is connected to ground. Once the signal lasts longer than 11 ms, the debouncer assumes the last
bounce is met and allows the AD5228 to increment by one step. If the PU signal remains at low and reaches t
characteristics apply to PD operation.

INTERFACE TIMING DIAGRAMS

t

PU

R

WB

PU

R

WB

PU

t

PU_REP

t

DB

Figure 2. Increment R

t

AS_START

t

DB

t

AS

Figure 3. Increment R

in Discrete Steps

WB

in Autoscan Mode

WB

04422-0-004

04422-0-005

Rev. 0 | Page 4 of 20

t

PU

R

WB

PD

t

PD_REP

t

DB

Figure 4. Decrement R

in Discrete Steps

WB

04422-0-006

PD

t

AS_START

t

R

WB

DB

Figure 5. Decrement R

t

AS

04422-0-007

in Autoscan Mode

WB

AD5228

ABSOLUTE MAXIMUM RATINGS

Table 3.

Parameter Rating

VDD to GND −0.3 V, +7 V
VA, VB, VW to GND 0 V, VDD

0 V, V

PU, PD, PRE Voltage to GND

DD

Maximum Current

IWB, IWA Pulsed ±20 mA
IWB Continuous (R

≤ 5 kΩ, A open)1 ±1 mA

WB

IWA Continuous (RWA ≤ 5 kΩ, B open)1 ±1 mA
IAB Continuous

= 10 kΩ/50 kΩ/100 kΩ)1

(R

AB

±500 µA/±100 µA/

±50 µA
Operating Temperature Range −40°C to +105°C
Maximum Junction Temperature

(T

max)

J

150°C

Storage Temperature −65°C to +150°C
Lead Temperature

245°C
(Soldering, 10 s – 30 s)

Thermal Resistance2 θJA 230°C/W

1

Maximum terminal current is bounded by the maximum applied voltage

across any two of the A, B, and W terminals at a given resistance, the
maximum current handling of the switches, and the maximum power
dissipation of the package. VDD = 5 V.

2

Package power dissipation = (TJmax – TA) / θJA.

Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only and functional operation of the device at these or
any other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.

ESD CAUTION

ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on
the human body and test equipment and can discharge without detection. Although this product features
proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy
electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance
degradation or loss of functionality.

Rev. 0 | Page 5 of 20

AD5228

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

PU

1

PD

2

A

3
4

GND

Figure 6. SOT-23-8 Pin Configuration

Table 4. Pin Function Descriptions

Pin No. Mnemonic Description

1

Push-Up Pin.

PU

Connect to the external pushbutton. Active low. A 100 kΩ pull-up resistor is connected to V

2

Push-Down Pin.

PD

Connect to the external pushbutton. Active low. A 100 kΩ pull-up resistor is connected to V
3 A Resistor Terminal A. GND ≤VA ≤ VDD.
4 GND Common Ground.
5 W Wiper Terminal W. GND ≤ VW ≤ VDD.
6 B Resistor Terminal B. GND ≤ VB ≤ VDD.
7 PRE

Power-On Preset. Output = midscale if PRE = GND; output = zero scale if PRE = V

No pull-up resistor is needed.
8 VDD Positive Power Supply, 2.7 V to 5.5 V.

AD5228

V

8

DD

PRE

7

B

6
5

W

04422-0-003

.

DD

.

DD

. Do not let the PRE pin float.

DD

Rev. 0 | Page 6 of 20