CAT5120, CAT5121, CAT5122
16-Tap MiniPot™ Digitally Programmable
Potentiometers with 2-Wire Interface
FeATures
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DesCrIPTIOn
CAT520/52/522 linear-taper digitally programmable
potentiometers perform the same function as a
mechanical potentiometer or a variable resistor. These
devices consist of a fixed resistor and a wiper contact
with 6-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.
Three resistance values are available: 10kΩ, 50kΩ and
100kΩ. These are available in space-saving 5-pin and
6-pin SC70 and SOT-23 packages.
0.3µA ultra-low supply current
single-supply operation: 2.7V to 5.5V
Glitchless switching between resistor taps
Power-on reset to midscale
2-Wire up/down serial interface
Resistance values: 10kΩ, 50kΩ and 100kΩ
Available in sC70 and sOT-23 packages
APPlICATIOns
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lCD screen adjustment
Volume control
Mechanical potentiometer replacement
Gain adjustment
line impedance matching
FunCTIOnAl DIAGrAM
H
V
DD
GND
UP-DOWN
COUNTER
For Ordering Information details, see page 10.
16-POSITION
DECODER
CS
W
U/D
PIn COnFIGurATIOn
sC70
sOT-23
V
DD
6 H
V
DD
sC70
sOT-23
5 H
L
PIn DesCrIPTIOns
name
Description
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
Doc. No. 22, Rev. C
GND 2
5 W
GND 2
V
DD
CAT5122
4 CS
CAT5120
U/D 3
4
CS
U/D 3
GND
U/D
sC70
sOT-23
CS
V
DD
6 H
GND 2
5 L
L
W
H
CAT5121
U/D 3
4
CS
© 2007 by Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
CAT5120, CAT5121, CAT5122
AbsOluTe MAxIMuM rATInGs
(1)
V
DD
to GND
All Other Pins to GND
Input and Output Latch-Up Immunity
Maximum
Continuous Current into H, L and W
100kΩ
50kΩ
10kΩ
Continuous Power Dissipation (T
A
= +70ºC)
5-pin SC70
(2)
6-pin SC70
(2)
Operating Temperature Range
Junction Temperature
Storage Temperature Range
Soldering Temperature (soldering, 0s)
247mW
245mW
-40ºC to +85ºC
+50ºC
-65ºC to +50ºC
+300ºC
-0.3V to +6V
-0.3V to (V
DD
+ 0.3)V
±200mA
±0.6mA
±.3mA
±.3mA
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.
(2) Derate 3.mW/ºC above T
A
= +70ºC
eleCTrICAl CHArACTerIsTICs
V
DD
= 2.7V to 5.5V, V
H
= V
DD
, V
L
= 0, T
A
= -40ºC to 85ºC. Typical values are at V
DD
= 2.7V, T
A
= 25ºC, unless
otherwise noted.
Parameter
DC Performance
Resolution
End-to-End Resistance (-00)
End-to-End Resistance (-50)
End-to-End Resistance (-0)
End-to-End Resistance Tempco
Ratiometric Resistance Tempco
Integral Nonlinearity
Differential Nonlinearity
Zero/Full-Scale Error
Wiper Resistance
Digital Inputs
Input High Voltage
Input Low Voltage
V
IH
V
IL
0.7 x V
DD
0.3 x V
DD
V
V
R
W
INL
DNL
±0.
200
TC
R
6
75
37.5
7.5
00
50
0
200
5
±0.5
±0.5
±0.5
600
25
62.5
2.5
ppm/ºC
ppm/ºC
LSB
LSB
LSB
Ω
kΩ
Taps
symbol
Conditions
Min
Typ
Max
units
Doc. No. 22, Rev. C
2
© 2007 by Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
CAT5120, CAT5121, CAT5122
eleCTrICAl CHArACTerIsTICs
(continued)
V
DD
= 2.7V to 5.5V, V
H
= V
DD
, V
L
= 0, T
A
= -40ºC to 85ºC. Typical values are at V
DD
= 2.7V, T
A
= 25ºC, unless
otherwise noted.
Parameter
U/DMode 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
()
Output Settling Time
Power supply
Supply Voltage
Active Supply Current
(3)
Standby Supply Current
(4)
V
DD
I
DD
I
SD
V
DD
= +5V
0.3
2.7
5.5
25
V
µA
µA
(2)
symbol
t
CU
t
CI
t
IC
t
IL
t
IH
f
TOGGLE
t
SETTLE
Conditions
Min
25
50
25
25
25
Typ
Max
units
ns
ns
ns
ns
ns
Timing Characteristics (Figures 1, 2)
100kΩ variable resistor
configuration, CL = 10pF
100kΩ potentiometer
configuration, CL = 10pF
MHz
μs
0.25
notes:
() Up/Down Toggle Rate: f
TOGGLE
= /t
SETTLE
(2) Typical setting times are dependant on end-to-end resistance.
(3) Supply current taken while changing wiper tap, f
TOGGLE
= MHz.
(4) Supply current taken while wiper position is fixed.
TyPICAl OPerATInG CHArACTerIsTICs
T
A
= 25ºC, unless otherwise noted.
V
DD
= 2.7V
50K
V
DD
= 5.5V
0
4
8
12
16
20
24
28
32
WIPER POSITION
V
DD
= 5.5V
V
DD
= 2.7V
© 2007 by Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
3
Doc No. 22, Rev. C
CAT5120, CAT5121, CAT5122
FunCTIOnAl DesCrIPTIOn
The CAT5120/5121/5122 consist of a fixed resistor
and a wiper contact with 6-tap points that are digitally
controlled through a 2-wire up/down serial interface.
Three end-to-end resistance values are available: 10kΩ,
50kΩ and 100kΩ.
The CAT520 is designed to operate as a potentiometer.
In this configuration, the low terminal of the resistor array
is connected to ground (pin 2).
The CAT522 performs as a variable resistor. In this
device, the wiper terminal and high terminal of the
resistor array is connected at pin 5. The CAT52 is
a similar variable resistor, except the low terminal is
connected to pin 5.
DIGITAl InTerFACe OPerATIOn
The Minipots 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 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 and 2).
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
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.
Figure 1. serial Interface Timing Diagram, Increment Mode
CS
t
CU
t
IL
U/D
t
CI
t
SETTLE
t
IC
t
IH
t
SETTLE
W
Note: "W" is not a digital signal. It represents wiper transitions.
Figure 2. serial Interface Timing Diagram, Decrement Mode
CS
t
CU
t
IH
U/D
t
IC
t
IL
t
CI
W
t
SETTLE
t
SETTLE
Note: "W" is not a digital signal. It represents wiper transitions.
Doc. No. 22, Rev. C
4
© 2007 by Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
CAT5120, CAT5121, CAT5122
APPlICATIOns InFOrMATIOn
The Minipots are intended for circuits requiring digitally
controlled adjustable resistance, such as LCD contrast
control, where voltage biasing adjusts the display
contrast.
AlTernATIVe POsITIVe lCD bIAs COnTrOl
Use an op amp to provide buffering and gain on the output
of the CAT520. Connect the mechanical potentiometer
to the positive input of a noninverting op amp (Figure 3) to
select a portion of the input signal by digitally controlling
the wiper terminal. Figure 4 shows a similar circuit for
the CAT52.
ADjusTAble GAIn
Figure 5 shows how to use the variable resistor to digitally
adjust the gain of a noninverting op amp configuration.
Connect the CAT52 in series with a resistor to ground
to form the adjustable gain control of a noninverting
amplifier. The Minipots have a low 5ppm/°C ratiometric
tempco that allows for a very stable adjustable gain
configuration over temperature.
Figure 3. Positive lCD bias Control
+5V
Figure 4. Positive lCD bias Control
+5V
H
H
30V
W
CAT5120
L
30V
V
OUT
CAT5121
L
V
OUT
Figure 5a. Adjustable Gain Circuit
V
CC
V
IN
V
OUT
Figure 5b. Adjustable Gain Circuit
V
CC
V
IN
V
OUT
H
W
L
H
CAT5121
L
CAT5120
© 2007 by Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
5
Doc No. 22, Rev. C
ST - Low Power RF
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