a
FEATURES
128 Position
Potentiometer Replacement
10 k , 50 k , 100 k
Very Low Power: 40 A Max
Increment/Decrement Count Control
APPLICATIONS
Mechanical Potentiometer Replacement
Remote Incremental Adjustment Applications
Instrumentation: Gain, Offset Adjustment
Programmable Voltage-to-Current Conversion
Programmable Filters, Delays, Time Constants
Line Impedance Matching
Power Supply Adjustment
GENERAL DESCRIPTION
CLK
CS
Increment/Decrement
Digital Potentiometer
AD5220
FUNCTIONAL BLOCK DIAGRAM
V
DD
EN
UP/
7
DOWN
CNTR
RS
POR
40
H
D
E
C
O
D
E
A
W
B
GND
U/D
AD5220
+5V
UP/DOWN
CS
U/D
CLK
The AD5220 provides a single channel, 128-position digitally
controlled variable resistor (VR) device. This device performs
the same electronic adjustment function as a potentiometer or
variable resistor. These products were optimized for instrument
and test equipment push-button applications. A choice between
bandwidth or power dissipation are available as a result of the
wide selection of end-to-end terminal resistance values.
The AD5220 contains a fixed resistor with a wiper contact that
taps the fixed resistor value at a point determined by a digitally
controlled UP/DOWN counter. The resistance between the
wiper and either end point of the fixed resistor provides a con-
stant resistance step size that is equal to the end-to-end resis-
tance divided by the number of positions (e.g., R
STEP
= 10 k鈩?
128 = 78
鈩?.
The variable resistor offers a true adjustable 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
10 k鈩? 50 k鈩? or 100 k鈩?has a nominal temperature coefficient
of 800 ppm/擄C.
The chip select
CS,
count CLK and U/D direction control
inputs set the variable resistor position. These inputs that con-
trol the internal UP/DOWN counter can be easily generated
with mechanical or push button switches (or other contact closure
devices). External debounce circuitry is required for the nega-
tive-edge sensitive CLK pin. This simple digital interface elimi-
nates the need for microcontrollers in front panel interface designs.
The AD5220 is available in both surface mount (SO-8) and the
8-lead plastic DIP package. For ultracompact solutions selected
models are available in the thin
碌SOIC
package. All parts are
guaranteed to operate over the extended industrial temperature
range of 鈥?0擄C to +85擄C. For 3-wire, SPI compatible inter-
face applications, see the AD7376/AD8400/AD8402/AD8403
products.
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
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
INCREMENT
AD5220
Figure 1. Typical Push-Button Control Application
50mV/DIV
UPCOUNT DETAIL
V
DD
= 5.5V
V
A
= 5.5V
V
B
= 0V
f = 100kHz
V
WB
5V/DIV
CLK
Figure 2a. Stair-Step Increment Output
V
DD
= 5.5V
V
A
= 5.5V
V
B
= 0V
f = 60kHz
COUNT
00
H
v
3F
H
v
00
H
V
WR
f
CLK
= 60kHz
Figure 2b. Full-Scale Up/Down Count
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
漏 Analog Devices, Inc., 1998
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