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PDF AD5228 Data sheet ( Hoja de datos )
| Número de pieza | AD5228 | |
| Descripción | 32-Position Manual Up/Down Control Potentiometer | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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32-Position Manual Up/Down Control
Potentiometer
AD5228
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, IDD = 0.4 μA typ and 3 μA max
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 potenti-
ometer operation1. Its simple up/down control interface allows
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 terms digital potentiometer and RDAC are used interchangeably.
FUNCTIONAL BLOCK DIAGRAM
VDD
PUSH-UP
BUTTON
PU
PD
PUSH-DOWN
BUTTON
UP/DOWN
CONTROL
LOGIC
R1 R2
DISCRETE
STEP/AUTO
SCAN DETECT
D AD5228
E
C
O
D
E
A
W
B
ADAPTIVE
DEBOUNCER
ZERO- OR MID-
SCALE PRESET
PRE
GND
Figure 1.
The AD5228 can increment or decrement the resistance in
discrete steps or in autoscan mode. When the PU or PD button
is pressed briefly (no longer than 0.6 s), the resistance of the
AD5228 changes by one step. When the PU or PD button is
held 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 PD Operation1
0 0 RWB Decrement
0 1 RWB Increment
1 0 RWB Decrement
1 1 RWB Does Not Change
1RWA increments if RWB decrements and vice versa.
Rev. A
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: 781.326.8703© 2004–2009Analog Devices, Inc. All rights reserved.
1 page  
ABSOLUTE MAXIMUM RATINGS
Table 3.
Parameter
Rating
VDD to GND
VA, VB, VW to GND
PU, PD, PRE Voltage to GND
−0.3 V, +7 V
0 V, VDD
0 V, VDD
Maximum Current
IWB, IWA Pulsed
IWB Continuous (RWB ≤ 5 kΩ, A open)1
IWA Continuous (RWA ≤ 5 kΩ, B open)1
IAB Continuous
(RAB = 10 kΩ/50 kΩ/100 kΩ)1
Operating Temperature Range
±20 mA
±1 mA
±1 mA
±500 μA/±100 μA/
±50 μA
−40°C to +105°C
Maximum Junction Temperature
(TJmax)
Storage Temperature
Lead Temperature
(Soldering, 10 s – 30 s)
Thermal Resistance2 θJA
150°C
−65°C to +150°C
245°C
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.
AD5228
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. A | Page 5 of 20
5 Page 
THEORY OF OPERATION
The AD5228 is a 32-position manual up/down digitally con-
trolled potentiometer with selectable power-on preset. The
AD5228 presets to midscale when the PRE pin is tied to ground
and to zero-scale when PRE is tied to VDD. Floating the PRE pin
is not allowed. The step-up and step-down operations require
the activation of the PU (push-up) and PD (push-down) pins.
These pins have 100 kΩ internal pull-up resistors that the PU
and PD activate at logic low. The common practice is to apply
external pushbuttons (tactile switches) as shown in Figure 30.
VDD
PUSH-UP
BUTTON
PU
PD
PUSH-DOWN
BUTTON
UP/DOWN
CONTROL
LOGIC
R1 R2
DISCRETE
STEP/AUTO
SCAN DETECT
D AD5228
E
C
O
D
E
A
W
B
ADAPTIVE
DEBOUNCER
ZERO- OR MID-
SCALE PRESET
PRE
GND
Figure 30. Typical Pushbutton Interface
Because of the bounce mechanism commonly found in the
switches during contact closures, a single pushbutton press
usually generates numerous bounces during contact closure.
Note that the term pushbutton refers specifically to a
pushbutton tactile switch or a similar switch that has 10 ms or
less bounce time during contact closure. Figure 31 shows the
characteristics of one such switch, the KRS-3550 tactile switch.
Figure 32 and Figure 33 show close ups of the initial bounces
and end bounces, respectively.
1
CH1 1.00V
M40.0ms
T 20.40%
A CH1 2.38V
Figure 31. Typical Tactile Switch Characteristics
AD5228
1
CH1 1.00V
M100μs
T 20.20%
A CH1 2.38V
Figure 32. Close-Up of Initial Bounces
1
CH1 1.00V
M10.0μs
T 20.20%
A CH1 2.38V
Figure 33. Close-Up of Final Bounces
The following paragraphs describes the PU incrementing
operation. Similar characteristics apply to the PD decrementing
operation.
The AD5228 features an adaptive debouncer that monitors the
duration of the logic-low level of PU signal between bounces. If
the PU logic-low level signal duration is shorter than 7 ms, the
debouncer ignores it as an invalid incrementing command.
Whenever the logic-low level of PU signal lasts longer than
11 ms, the debouncer assumes that the last bounce is met and
therefore increments RWB by one step.
Repeatedly pressing the PU button for fast adjustment without
missing steps is allowed, provided that each press is not shorter
than tPU, which is 12 ms (see Figure 2). As a point of reference,
an advanced video game player can press a pushbutton switch
in 40 ms.
Rev. A | Page 11 of 20
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet AD5228.PDF ] | |
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