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1-/2-/4-Channel
Digital Potentiometers
AD8400/AD8402/AD8403
FEATURES
256-position variable resistance device
Replaces 1, 2, or 4 potentiometers
1 kΩ, 10 kΩ, 50 kΩ, 100 kΩ
Power shutdown—less than 5
μA
3-wire,SPI-compatible serial data input
10 MHz update data loading rate
2.7 V to 5.5 V single-supply operation
Qualified for automotive applications
V
DD
DGND
FUNCTIONAL BLOCK DIAGRAM
AD8403
DAC
SELECT
1
2
3
A1, A0 4
2
10-BIT
SERIAL
LATCH
SDI
CLK
CS
8-BIT 8
LATCH
CK RS
D
CK Q RS
8
8-BIT
LATCH
CK RS
8-BIT 8
LATCH
CK RS
RDAC1
A1
W1
B1
AGND1
A2
W2
B2
AGND2
A3
W3
B3
AGND3
A4
W4
B4
AGND4
01092-001
SHDN
8
RDAC2
SHDN
8
RDAC3
APPLICATIONS
Mechanical potentiometer replacement
Programmable filters, delays, time constants
Volume control, panning
Line impedance matching
Power supply adjustment
8-BIT
LATCH
CK RS
SHDN
RDAC4
SHDN
SDO
RS
SHDN
GENERAL DESCRIPTION
The AD8400/AD8402/AD8403 provide a single-, dual-, or
quad-channel, 256-position, digitally controlled variable resistor
(VR) device.
1
These devices perform the same electronic adjust-
ment function as a mechanical potentiometer or variable
resistor. The AD8400 contains a single variable resistor in the
compact SOIC-8 package. The AD8402 contains two independent
variable resistors in space-saving SOIC-14 surface-mount
packages. The AD8403 contains four independent variable
resistors in 24-lead PDIP, SOIC, and TSSOP packages. Each
part contains a fixed resistor with a wiper contact that taps the
fixed resistor value at a point determined by the digital code
loaded into the controlling serial input register. The resistance
between the wiper and either endpoint of the fixed resistor
varies linearly with respect to the digital code transferred into
the VR latch. Each variable resistor offers a completely
programmable value of resistance between the A terminal and
the wiper or the B terminal and the wiper. The fixed A-to-B
terminal resistance of 1 kΩ, 10 kΩ, 50 kΩ, or 100 kΩ has a ±1%
channel-to-channel matching tolerance with a nominal
temperature coefficient of 500 ppm/°C. A unique switching
circuit minimizes the high glitch inherent in traditional
switched resistor designs, avoiding any make-before-break
or break-before-make operation.
(continued on Page 3)
1
Figure 1.
100
R
WA
R
WA
(D), R
WB
(D) (% of Nominal R
AB
)
R
WB
75
50
25
0
64
128
CODE (Decimal)
192
255
Figure 2. R
WA
and R
WB
vs. Code
The terms digital potentiometer, VR, and RDAC are used interchangeably.
Rev. E
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: 781.329.4700
www.analog.com
Fax: 781.461.3113
© 2010 Analog Devices, Inc. All rights reserved.
01092-002
0
AD8400/AD8402/AD8403
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications ....................................................................................... 1
General Description ......................................................................... 1
Functional Block Diagram .............................................................. 1
Revision History ............................................................................... 2
Specifications..................................................................................... 4
Electrical Characteristics—10 kΩ Version................................ 4
Electrical Characteristics—50 kΩ and 100 kΩ Versions......... 6
Electrical Characteristics—1 kΩ Version .................................. 8
Electrical Characteristics—All Versions ................................. 10
Timing Diagrams........................................................................ 10
Absolute Maximum Ratings.......................................................... 11
Serial Data-Word Format .......................................................... 11
ESD Caution................................................................................ 11
Pin Configurations and Function Descriptions ......................... 12
Typical Performance Characteristics ........................................... 14
Test Circuits ..................................................................................... 19
Theory of Operation ...................................................................... 20
Programming the Variable Resistor ......................................... 20
Programming the Potentiometer Divider ............................... 21
Digital Interfacing ...................................................................... 21
Applications..................................................................................... 24
Active Filter ................................................................................. 24
Outline Dimensions ....................................................................... 26
Ordering Guide .......................................................................... 30
Automotive Products ................................................................. 31
REVISION HISTORY
7/10—Rev. D to Rev. E
Changes to Features Section ............................................................ 1
Changes to I
AB
Continuous Current Parameter (Table 5) .........11
Updated Outline Dimensions ........................................................26
Changes to Ordering Guide ...........................................................30
Added Automotive Products Section ...........................................31
10/05—Rev. C to Rev. D
Updated Format .................................................................. Universal
Changes to Features........................................................................... 1
Changes to Table 1 ............................................................................. 4
Changes to Table 2 ............................................................................. 6
Changes to Table 3 ............................................................................. 8
Changes to Table 5 ...........................................................................11
Added Figure 36...............................................................................18
Replaced Figure 37 ..........................................................................19
Changes to Theory of Operation Section .....................................20
Changes to Applications Section ...................................................24
Updated Outline Dimensions ........................................................26
Changes to Ordering Guide ...........................................................28
11/01—Rev. B to Rev. C
Addition of new Figure ..................................................................... 1
Edits to Specifications ....................................................................... 2
Edits to Absolute Maximum Ratings .............................................. 6
Edits to TPCs 1, 8, 12, 16, 20, 24, 35 ............................................... 9
Edits to
the Pro
gramming the Variable Resistor Section .......................... 13
Rev. E | Page 2 of 32
AD8400/AD8402/AD8403
GENERAL DESCRIPTION
(continued from Page 1)
Each VR has its own VR latch that holds its programmed
resistance value. These VR latches are updated from an SPI-
compatible, serial-to-parallel shift register that is loaded from
a standard 3-wire, serial-input digital interface. Ten data bits
make up the data-word clocked into the serial input register.
The data-word is decoded where the first two bits determine
the address of the VR latch to be loaded, and the last eight bits
are the data. A serial data output pin at the opposite end of the
serial register allows simple daisy chaining in multiple VR
applications without additional external decoding logic.
The reset (RS) pin forces the wiper to midscale by loading 80
H
into the VR latch. The SHDN pin forces the resistor to an end-
to-end open-circuit condition on the A terminal and shorts the
wiper to the B terminal, achieving a microwatt power shutdown
state. When SHDN is returned to logic high, the previous latch
settings put the wiper in the same resistance setting prior to
shutdown. The digital interface is still active in shutdown so
that code changes can be made that will produce new wiper
positions when the device is taken out of shutdown.
The AD8400 is available in the SOIC-8 surface mount. The
AD8402 is available in both surface-mount (SOIC-14) and
14-lead PDIP packages, while the AD8403 is available in a
narrow-body, 24-lead PDIP and a 24-lead, surface-mount
package. The AD8402/AD8403 are also offered in the 1.1 mm
thin TSSOP-14/TSSOP-24 packages for PCMCIA applications.
All parts are guaranteed to operate over the extended industrial
temperature range of −40°C to +125°C.
Rev. E | Page 3 of 32
AD8400/AD8402/AD8403
SPECIFICATIONS
ELECTRICAL CHARACTERISTICS—10 KΩ VERSION
V
DD
= 3 V ± 10% or 5 V ± 10%, V
A
= V
DD
, V
B
= 0 V, −40°C ≤ T
A
≤ +125°C, unless otherwise noted.
Table 1.
Parameter
Symbol
Conditions
DC CHARACTERISTICS RHEOSTAT MODE (Specifications Apply to All VRs)
Resistor Differential NL
2
R-DNL
R
WB
, V
A
= no connect
2
Resistor Nonlinearity
R-INL
R
WB
, V
A
= no connect
3
Nominal Resistance
R
AB
T
A
= 25°C, model: AD840XYY10
Resistance Tempco
ΔR
AB
/ΔT
V
AB
= V
DD
, wiper = no connect
Wiper Resistance
R
W
V
DD
= 5V, I
W
= V
DD
/R
AB
R
W
V
DD
= 3V, I
W
= V
DD
/R
AB
Nominal Resistance Match
ΔR/R
AB
CH 1 to CH 2, CH 3, or CH 4, V
AB
= V
DD
, T
A
= 25°C
DC CHARACTERISTICS POTENTIOMETER DIVIDER (Specifications Apply to All VRs)
Resolution
N
4
Integral Nonlinearity
INL
4
Differential Nonlinearity
DNL
V
DD
= 5 V
DNL
V
DD
= 3 V, T
A
= 25°C
DNL
V
DD
= 3 V, T
A
= −40°C to +85°C
Voltage Divider Tempco
ΔV
W
/ΔT
Code = 80
H
Full-Scale Error
V
WFSE
Code = FF
H
Zero-Scale Error
V
WZSE
Code = 00
H
RESISTOR TERMINALS
Voltage Range
5
V
A, B, W
6
Capacitance Ax, Capacitance Bx C
A, B
f = 1 MHz, measured to GND, code = 80
H
6
Capacitance Wx
C
W
f = 1 MHz, measured to GND, code = 80
H
7
Shutdown Current
I
A_SD
V
A
= V
DD
, V
B
= 0 V, SHDN = 0
Shutdown Wiper Resistance
R
W_SD
V
A
= V
DD
, V
B
= 0 V, SHDN = 0, V
DD
= 5 V
DIGITAL INPUTS AND OUTPUTS
Input Logic High
V
IH
V
DD
= 5 V
Input Logic Low
V
IL
V
DD
= 5 V
Input Logic High
V
IH
V
DD
= 3 V
Input Logic Low
V
IL
V
DD
= 3 V
Output Logic High
V
OH
R
L
= 2.2 kΩ to V
DD
Output Logic Low
V
OL
I
OL
= 1.6 mA, V
DD
= 5 V
Input Current
I
IL
V
IN
= 0 V or 5 V, V
DD
= 5 V
Input Capacitance
6
C
IL
POWER SUPPLIES
Power Supply Range
V
DD
range
Supply Current (CMOS)
I
DD
V
IH
= V
DD
or V
IL
= 0 V
Supply Current (TTL)
8
I
DD
V
IH
= 2.4 V or 0.8 V, V
DD
= 5.5 V
9
Power Dissipation (CMOS)
P
DISS
V
IH
= V
DD
or V
IL
= 0 V, V
DD
= 5.5 V
Power Supply Sensitivity
PSS
V
DD
= 5 V ± 10%
PSS
V
DD
= 3 V ± 10%
Min
−1
−2
8
Typ
1
±1/4
±1/2
10
500
50
200
0.2
Max
+1
+2
12
100
1
Unit
LSB
LSB
kΩ
ppm/°C
Ω
Ω
%
Bits
LSB
LSB
LSB
LSB
ppm/°C
LSB
LSB
V
pF
pF
μA
Ω
V
V
V
V
V
V
μA
pF
V
μA
mA
μW
%/%
%/%
8
−2
−1
−1
−1.5
−4
0
0
±1/2
±1/4
±1/4
±1/2
15
−2.8
1.3
+2
+1
+1
+1.5
0
2
V
DD
75
120
0.01
100
2.4
5
200
0.8
2.1
0.6
V
DD
− 0.1
0.4
±1
5
2.7
0.01
0.9
0.0002
0.006
5.5
5
4
27.5
0.001
0.03
Rev. E | Page 4 of 32
Embedded System
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