CAT5120, CAT5121,
CAT5122
16‐tap Digital
Potentiometers (POTs)
with 2‐wire Interface
Description
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CAT5120/5121/5122 linear-taper digital POTs perform the same
function as a mechanical potentiometer or a variable resistor. These
devices consist of a fixed resistor and a wiper contact with 16-tap
points that are digitally controlled through a 2-wire up/down serial
interface.
The CAT5120 is configured as a potentiometer. The CAT5121 and
CAT5122 are configured as variable resistors. See
Pin Configurations
for part functionality.
Two resistance values are available: 10 kW and 50 kW. These are
available in space-saving 5-pin and 6-pin SC−70 and SOT−23
packages.
Features
SC−70
SD SUFFIX
CASE 419AD
SOT−23
TB SUFFIX
CASE 527AJ
SC−70
SD SUFFIX
CASE 419AC
SOT−23
TB SUFFIX
CASE 527AH
0.3
mA
Ultra-low Standby Current
Single-supply Operation: 2.7 V to 5.5 V
Glitchless Switching between Resistor Taps
Power-on Reset to Midscale
2-wire Up/Down Serial Interface
Resistance Values: 10 kW, 50 kW
Available in SC−70 and SOT−23 Packages
These Devices are Pb-Free, Halogen Free/BFR Free and are RoHS
Compliant
LCD Screen Adjustment
Volume Control
Mechanical Potentiometer Replacement
Gain Adjustment
Line Impedance Matching
PIN CONFIGURATIONS
SC−70
SOT−23
V
DD
1
GND 2
U/D 3
CAT5120
6 H
5 W
4 CS
Applications
SC−70
SOT−23
V
DD
1
6 H
5 L
CAT5121
U/D 3
SC−70
SOT−23
V
DD
1
GND 2
CAT5122
U/D 3
4 CS
5 H
4 CS
GND 2
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 7 of this data sheet.
Semiconductor Components Industries, LLC, 2013
July, 2013
−
Rev. 8
1
Publication Order Number:
CAT5120/D
CAT5120, CAT5121, CAT5122
H
V
DD
GND
16−POSITION
DECODER
UP−DOWN
COUNTER
CS
W
U/D
L
Figure 1. Functional Diagram
Table 1. PIN DESCRIPTIONS
Name
V
DD
GND
U/D
CS
L
W
H
Power Supply
Ground
Up/Down Control Input. With CS low, a low-to-high transition increments or decrements the wiper position.
Chip Select Input. A high-to-low CS transition determines the mode: increment if U/D is high, or decrement if U/D is low.
Low Terminal of Resistor
Wiper Terminal of Resistor
High Terminal of Resistor
Description
Table 2. ABSOLUTE MAXIMUM RATINGS
Parameters
V
DD
to GND
All Other Pins to GND
Input and Output Latch-up Immunity
Maximum Continuous Current into H, L and W
50 kW
10 kW
Continuous Power Dissipation (T
A
= +70C)
5-pin SC−70 (Note 1)
6-pin SC−70 (Note 1)
Operating Temperature Range
Junction Temperature
Storage Temperature Range
Soldering Temperature (soldering, 10 s)
Ratings
−0.3
to +6
−0.3
to (V
DD
+ 0.3)
200
1.3
1.3
247
245
−40
to +85
+150
−65
to +150
+300
mW
Units
V
V
mA
mA
C
C
C
C
Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the
Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect
device reliability.
1. Derate 3.1 mW/C above T
A
= +70C
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CAT5120, CAT5121, CAT5122
Table 3. ELECTRICAL CHARACTERISTICS
Parameter
DC PERFORMANCE
Resolution
End-to-End Resistance (−50)
End-to-End Resistance (−10)
End-to-End Resistance Tempco
Ratiometric Resistance Tempco
Integral Non-linearity
Differential Non-linearity
Zero/Full-Scale Error
Wiper Resistance
DIGITAL INPUTS
Input High Voltage
Input Low Voltage
TIMING CHARACTERISTICS
(Figures 7, 8)
U/D Mode to CS Setup
CS to U/D Step Setup
CS to U/D Step Hold
U/D Step Low Period
U/D Step High Period
Up/Down Toggle Rate (Note 2)
Output Settling Time (Note 3)
t
CU
t
CI
t
IC
t
IL
t
IH
f
TOGGLE
t
SETTLE
50 kW variable resistor
configuration, C
L
= 10 pF
50 kW potentiometer
configuration, C
L
= 10 pF
POWER SUPPLY
Supply Voltage
Active Supply Current (Note 4)
Standby Supply Current (Note 5)
2.
3.
4.
5.
V
DD
I
DD
I
SB
V
DD
= +5 V
0.3
2.7
5.5
25
1
V
mA
mA
25
50
25
25
25
1
1
0.25
ns
ns
ns
ns
ns
MHz
ms
V
IH
V
IL
0.7 x V
DD
0.3 x V
DD
V
V
R
W
INL
DNL
0.1
200
TC
R
16
37.5
7.5
50
10
200
5
0.5
0.5
0.5
600
62.5
12.5
ppm/C
ppm/C
LSB
LSB
LSB
W
Taps
kW
(V
DD
= 2.7 V to 5.5 V, V
H
= V
DD
, V
L
= 0, T
A
=
−40C
to +85C. Typical values are at V
DD
= 2.7 V, T
A
= 25C, unless otherwise noted.)
Symbol
Conditions
Min
Typ
Max
Units
Up/Down Toggle Rate: f
TOGGLE
= 1 / t
SETTLE
Typical settling times are dependent on end-to-end resistance.
Supply current measured while changing wiper tap, f
TOGGLE
= 1 MHz.
Supply current measured while wiper position is fixed.
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CAT5120, CAT5121, CAT5122
TYPICAL OPERATING CHARACTERISTICS
(T
A
= 25C, unless otherwise noted.)
250
WIPER RESISTANCE (W)
200
150
100
50
0
V
DD
= 5.5 V
END−TO−END RESISTANCE
CHANGE (%)
1.5
1.0
0.5
50 K
0
−0.5
−1.0
−1.5
−2.0
−50
0
50
TEMPERATURE (C)
100
150
V
DD
= 2.7 V
0
4
8
12
16
20
24
28
32
WIPER POSITION
Figure 2. Wiper Resistance vs. Tap Position
120
100
RESISTANCE (kW)
100 k
CURRENT (mA)
80
60
40
20
0
50 k
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
10 k
1 3
5
7
9 11 13 15 17 19 21 23 25 27 29 31
TAP POSITION
0.05
Figure 3. Change in End-to-End Resistance vs.
Temperature
V
DD
= 5.5 V
V
DD
= 2.7 V
0
−50
0
50
TEMPERATURE (C)
100
150
Figure 4. W-to-L Resistance vs. Tap Position
Figure 5. Supply Current vs. Temperature
U/D
2 V/div
Wiper
Output
100 mV/div
200 ns/div
Figure 6. Tap-to-Tap Switching Transient
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CAT5120, CAT5121, CAT5122
FUNCTIONAL DESCRIPTION
The CAT5120/5121/5122 consist of a fixed resistor and a
wiper contact with 16-tap points that are digitally controlled
through a 2-wire up/down serial interface. Two end-to-end
resistance values are available: 10 kW and 50 kW.
The CAT5120 is designed to operate as a potentiometer.
In this configuration, the low terminal of the resistor array
is connected to ground (pin 2).
The CAT5122 performs as a variable resistor. In this
device, the wiper terminal and high terminal of the resistor
array is connected at pin 5. The CAT5121 is a similar
variable resistor, except the low terminal is connected to
pin 5.
Digital Interface Operation
low, the part will go into increment mode if U/D input is
high, and into decrement mode when U/D input is low. Once
the mode is set, the device will remain in that mode until CS
goes high again. A low-to-high transition at the U/D pin will
increment or decrement the wiper position depending on the
current mode (Figures 7 and 8).
When the CS input transitions to high (serial interface
inactive), the value of the counter is stored and the wiper
position is maintained.
Note that when the wiper reaches the maximum (or
minimum) tap position, the wiper will not wrap around to the
minimum (or maximum) position.
Power-on Reset
The devices have two modes of operation when the serial
interface is active: increment and decrement mode. The
serial interface is only active when CS is low.
The CS and U/D inputs control the position of the wiper
along the resistor array. When CS transitions from high to
CS
t
CU
t
IL
U/D
t
CI
t
SETTLE
W
Note: “W” is not a digital signal. It represents wiper transitions.
All parts in this family feature power-on reset (POR)
circuitry that sets the wiper position to midscale at
power-up. By default, the chip is in the increment mode.
t
IC
t
IH
t
SETTLE
Figure 7. Serial Interface Timing Diagram, Increment Mode
CS
t
CU
U/D
t
IC
t
IH
t
IL
W
t
CI
t
SETTLE
t
SETTLE
Note: “W” is not a digital signal. It represents wiper transitions.
Figure 8. Serial Interface Timing Diagram, Decrement Mode
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