CAT5128
32-Tap Digital Up/Down Control Potentiometer
FEATURES
32-position linear taper potentiometer
Low power CMOS technology
Single supply operation: 2.5V – 5.5V
Discrete step-up/step-down digital control
Resistance values: 10kΩ, 50kΩ and 100kΩ
Available in SOT-23 8-lead Pb-free package
DESCRIPTION
The CAT5128 is a single digitally programmable
potentiometer (DPP™) designed as an electronic
replacement for mechanical potentiometers and trim
pots. Ideal for automated adjustments on high volume
production lines, they are also well suited for
applications where equipment requiring periodic
adjustment is either difficult to access or located in a
hazardous or remote environment.
The CAT5128 contains a 32-tap series resistor array
connected between two terminals A and B. An
up/down counter and decoder that are controlled by
two input pins, determines which tap is connected to
the wiper, W. Wiper-control of the CAT5128 is
¯¯
accomplished with two input control pins, UP and
¯¯¯¯¯¯. A high-to-low transition on the UP input
¯¯
DOWN
increments the wiper position and a high-to-low
transition on the ¯¯¯¯¯¯ input decrements the wiper
DOWN
position. The tap position is not stored in memory.
The wiper is always set to the mid point, tap 15 at
power up.
The digitally programmable potentiometer can be used
as a three-terminal resistive divider or as a two-terminal
variable resistor. DPPs bring variability and program-
mability to a wide variety of applications including
control, parameter adjustments, and signal processing.
APPLICATIONS
Automated product calibration
Remote control adjustments
Offset, gain and zero control
Tamper-proof calibrations
Contrast, brightness and volume controls
Motor controls and feedback systems
Programmable analog functions
For Ordering Information details, see page 7.
FUNCTIONAL DIAGRAM
5-BIT
UP/DOWN
COUNTER
31
30
A
A
V
CC
A
UP
UP/DOWN
Control
DOWN
Power On Recall
GND
B
DOWN
W
V
CC
29
ONE 28
OF
THIRTY TWO
DECODER
CONTROL
CIRCUITRY
2
1
UP
TRANSFER
GATES
RESISTOR
ARRAY
W
GND
0
B
W
B
Electronic Potentiometer
Implementation
General
Detailed
© 2008 SCILLC. All rights reserved.
Characteristics subject to change without notice
1
Doc. No. MD-2128 Rev. B
CAT5128
PIN CONFIGURATION
SOT-23 8-Lead
¯¯
UP
¯¯¯¯¯¯
DOWN
A
GND
1
2
3
4
8
V
CC
NC
B
W
7
6
5
PIN DESCRIPTIONS
Name Function
¯¯
Step-Up Control
UP
¯¯¯¯¯¯ Step-Down Control
DOWN
A
GND
W
B
NC
V
CC
Potentiometer High Terminal
Ground
Wiper Terminal
Potentiometer Low Terminal
Not Connected
Supply Voltage
CAT
PIN DESCRIPTION
¯¯
UP:
Step-Up Control Input
When ¯¯¯¯¯¯ input is high, a high-to-low transition on
DOWN
¯¯
UP input will cause the wiper to move one increment
toward the A terminal.
¯¯¯¯¯¯:
Step-Down Control Input
DOWN
A high-to-low transition on ¯¯¯¯¯¯ input will cause the
DOWN
wiper to move one increment towards the B terminal.
A:
High End Potentiometer Terminal
A is the high end terminal of the potentiometer. It is
not required that this terminal be connected to a
potential greater than the B terminal. Voltage applied
to the A terminal cannot exceed the supply voltage,
V
CC
or go below ground, GND.
W:
Wiper Potentiometer Terminal
W is the wiper terminal of the potentiometer. Its
position on the resistor array is controlled by the
¯¯
control inputs, UP and ¯¯¯¯¯¯.
Voltage applied to the
DOWN
W terminal cannot exceed the supply voltage, V
CC
or
go below ground, GND.
B:
Low End Potentiometer Terminal
B is the low end terminal of the potentiometer. It is not
required that this terminal be connected to a potential
less than the A terminal. Voltage applied to the B
terminal cannot exceed the supply voltage, V
CC
or go
below ground, GND. B and A are electrically
interchangeable.
DEVICE OPERATION
The CAT5128 operates like a digitally controlled
potentiometer with A and B equivalent to the high and
low terminals and W equivalent to the mechanical
potentiometer's wiper. There are 32 available tap
positions including the resistor end points, A and B.
There are 31 resistor elements connected in series
between the A and B terminals. The wiper terminal is
connected to one of the 32 taps and controlled by two
¯¯
inputs, UP and ¯¯¯¯¯¯. These inputs control a five-bit
DOWN
up/down counter whose output is decoded to select
the wiper position.
A high-to-low transition on ¯¯¯¯¯¯ input will
DOWN
decrement one step the wiper position (R
WB
will
decrease with 1LSB and R
WA
will increase with 1LSB).
If and only if ¯¯¯¯¯¯ input is high, a high-to-low
DOWN
¯¯ input will increment one step the
transition on UP
wiper position (R
WB
will increase with 1LSB and R
WA
will decrease with 1LSB).
The wiper, when at either fixed terminal, acts like its
mechanical equivalent and does not move beyond the
last position. When the CAT5128 is powered-down,
the wiper position is reset. When power is restored,
the counter is set to the mid point, tap 15.
Doc. No. MD-2128 Rev. B
2
© 2008 SCILLC. All rights reserved.
Characteristics subject to change without notice
CAT5128
OPERATION MODES
¯¯
UP
High to Low
X
High
High to Low
Low
High
¯¯¯¯¯¯
DOWN
High
Low
High to Low
High to Low
X
High
Operation
Wiper toward A – R
W
Increment
Wiper does not change
Wiper toward B – R
W
Decrement
Wiper toward B – R
W
Decrement
Wiper does not change
Wiper does not change
C
B
B
R
B
C
A
A
R
A
R
W
W
C
W
Potentiometer
Equivalent Circuit
ABSOLUTE MAXIMUM RATINGS
(1)
Parameters
Supply Voltage
V
CC
to GND
Inputs
¯¯
UP to GND
¯¯¯¯¯¯ to GND
DOWN
A, B, W to GND
Operating Ambient Temperature
Industrial (‘I’ suffix)
Junction Temperature
Storage Temperature
Lead Soldering (10 seconds max)
Thermal Resistance
θ
JA
DC ELECTRICAL CHARACTERISTICS
(1)
V
CC
= +2.5V to +5.5V unless otherwise specified
Power Supply
Symbol
V
CC
I
CC1
I
SB1(3)
Parameter
Operating Voltage Range
Supply Current (Increment)
Supply Current (Standby)
V
CC
= 5.5V, f = 1MHz, I
W
= 0
V
CC
= 5.5V, f = 250kHz, I
W
= 0
¯¯ DOWN
UP, ¯¯¯¯¯¯ = V
CC
or GND
Conditions
Min
2.5
–
–
–
Typ
–
–
–
0.01
Max
5.5
100
50
1
Units
V
µA
µA
µA
-40 to +85
+150
-65 to 150
+300
230
ºC
ºC
ºC
ºC
ºC/W
-0.5 to V
CC
+0.5
-0.5 to V
CC
+0.5
-0.5 to V
CC
+0.5
V
V
V
-0.5 to +7V
V
Ratings
Units
Notes:
(1) Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings
only, and functional operation of the device at these or any other conditions outside of those listed in the operational sections of this
specification is not implied. Exposure to any absolute maximum rating for extended periods may affect device performance and reliability.
© 2008 SCILLC. All rights reserved.
Characteristics subject to change without notice
3
Doc. No. MD-2128 Rev. B
CAT5128
LOGIC INPUTS
V
CC
= +2.5V to +5.5V unless otherwise specified
Symbol
I
IH
I
IL
V
IH1
V
IL1
V
IH2
V
IL2
Parameter
Input Leakage Current
Input Leakage Current
TTL High Level Input Voltage
TTL Low Level Input Voltage
CMOS High Level Input Voltage
CMOS Low Level Input Voltage
Conditions
V
IN
= V
CC
V
IN
= 0V
4.5V
≤
V
CC
≤
5.5V
2.5V
≤
V
CC
≤
5.5V
Min
–
–
2
0
V
CC
x 0.7
-0.3
Typ
–
–
–
–
–
–
Max
10
-10
V
CC
0.8
V
CC
+ 0.3
V
CC
x 0.2
Units
µA
µA
V
V
V
V
POTENTIOMETER CHARACTERISTICS
V
CC
= +2.5V to +5.5V unless otherwise specified
Symbol
R
POT
Parameter
Potentiometer Resistance
Pot. Resistance Tolerance
V
A
V
B
INL
DNL
R
WI
I
W
TC
RPOT
TC
RATIO
V
N (3)
C
A
/C
B
/C
W
fc (3)
Voltage on A pin
Voltage on B pin
Resolution
Integral Linearity Error
Differential Linearity Error
Wiper Resistance
Wiper Current
TC of Pot Resistance
Ratiometric TC
Noise
Potentiometer Capacitances
Frequency Response
I
W
≤
2µA
I
W
≤
2µA
V
CC
= 5V, I
W
= 1mA
V
CC
= 2.5V, I
W
= 1mA
(2)
(3)
(3)
100kHz / 1kHz
(3)
Passive Attenuator, 10kΩ
50
5
8/24
8/8/25
1.7
20
-0.5
-0.5
0
0
3.2
0.1
0.05
70
150
300
1
0.5
0.5
Conditions
-10 Device
-50 Device
-00 Device
Min
Typ
10
50
100
±20
V
CC
V
CC
%
V
V
%
LSB
LSB
Ω
Ω
mA
ppm/ºC
ppm/ºC
nV/√Hz
pF
MHz
(1)
Max
Units
kΩ
Notes:
(1) Typical values are for T
A
= 25ºC and nominal supply voltage.
(2) I
W
= source or sink.
(3) These parameters are periodically sampled and are not production tested.
Doc. No. MD-2128 Rev. B
4
© 2008 SCILLC. All rights reserved.
Characteristics subject to change without notice
CAT5128
AC CONDITIONS OF TEST
V
CC
Range
Input Pulse Levels
Input Rise and Fall Times
Input Reference Levels
2.5V
≤
V
CC
≤
5.5V
0.2V
CC
to 0.7V
CC
10ns
0.5V
CC
AC OPERATING CHARACTERISTICS
V
CC
= +2.5V to +5.5V, V
H
= V
CC
, V
L
= 0V, unless othewise specified
Symbol
t
UP
t
DOWN
t
UP_CYC
t
DOWN_CYC
t
UP_R,
t
UP_F(2)
t
DOWN_R,
t
DOWN_F(2)
t
UP_SET
t
DOWN_SET
t
PU(2)
Parameter
¯¯
UP LOW Period
¯¯¯¯¯¯ LOW Period
DOWN
¯¯
UP Cycle Time
¯¯¯¯¯¯ Cycle Time
DOWN
¯¯
UP Rise and Fall Time
¯¯¯¯¯¯ Rise and Fall Time
DOWN
¯¯
UP Settling Time
¯¯¯¯¯¯ Settling Time
DOWN
Power-up to Wiper Stable
Min
500
500
1
1
–
–
200
200
–
Typ
–
–
–
–
–
–
–
–
–
(1)
Max
–
–
–
–
500
500
–
–
1
Units
ns
ns
µs
µs
ns
ns
ns
ns
ms
INTERFACE TIMING DIAGRAM
t
UP_CYC
t
UP
UP
t
UP_R
90%
10%
90%
10%
t
UP_F
MI
(3)
t
UP_SET
R
W
Increment R
W
in Discrete Steps
t
DOWN_CYC
t
DOWN
DOWN
t
DOWN_R
90%
10%
90%
10%
t
DOWN_F
t
DOWN_SET
R
W
MI
(3)
Decrement R
W
in Discrete Steps
Notes:
(1) Typical values are for T
A
= 25ºC and nominal supply voltage.
(2) This parameter is periodically sampled and not 100% tested.
(3) MI in the A.C. Timing diagram refers to the minimum incremental change in the W output due to a change in the wiper position.
© 2008 SCILLC. All rights reserved.
Characteristics subject to change without notice
5
Doc. No. MD-2128 Rev. B
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