
CAT5112
2
Doc. No. 2002, Rev. L
of the CAT5112 and is active low. When in a high
state, activity on the
INC
and U/
D
inputs will not
affect or change the position of the wiper.
DEVICE OPERATION
The CAT5112 operates like a digitally controlled
potentiometer with R
H
and R
L
equivalent to the high
and low terminals and R
WB
equivalent to the mechanical
potentiometer's wiper. There are 32 available tap posi-
tions including the resistor end points, R
H
and R
L
. There
are 31 resistor elements connected in series between
the R
H
and R
L
terminals. The wiper terminal is
connected to one of the 32 taps and controlled by three
inputs,
INC
, U/
D
and
CS
. These inputs control a five-bit
up/down counter whose output is decoded to select the
wiper position. The selected wiper position can be
stored in nonvolatile memory using the
INC
and
CS
inputs.
With
CS
set LOW the CAT5112 is selected and will
respond to the U/
D
and
INC
inputs. HIGH to LOW
transitions on
INC
wil increment or decrement the
wiper (depending on the state of the U/
D
input and five-
bit counter). The wiper, when at either fixed terminal,
acts like its mechanical equivalent and does not move
beyond the last position. The value of the counter is
stored in nonvolatile memory whenever
CS
transitions
HIGH while the
INC
input is also HIGH. When the
CAT5112 is powered-down, the last stored wiper counter
position is maintained in the nonvolatile memory. When
power is restored, the contents of the memory are
recalled and the counter is set to the value stored.
With
INC
set low, the CAT5112 may be de-selected
and powered down without storing the current wiper
position in nonvolatile memory. This allows the
system to always power up to a preset value stored
in nonvolatile memory.
PIN DESCRIPTIONS
INC
: Increment Control Input
The
INC
input (on the falling edge) moves the wiper in the
up or down direction determined by the condition of the
U/
D
input.
U/
D
: Up/Down Control Input
The U/
D
input controls the direction of the wiper
movement. When in a high state and
CS
is low, any high-
to-low transition on
INC
will cause the wiper to move one
increment toward the R
H
terminal. When in a low state
and
CS
is low, any high-to-low transition on
INC
will
cause the wiper to move one increment towards the
R
L
terminal.
R
H:
High End Potentiometer Terminal
R
H
is the high end terminal of the potentiometer. It is not
required that this terminal be connected to a potential
greater than the R
L
terminal. Voltage applied to the R
H
terminal cannot exceed the supply voltage, V
CC
or go
below ground, GND.
R
WB
: Wiper Potentiometer Terminal (Buffered)
R
WB
is the buffered wiper terminal of the potentiometer. Its
position on the resistor array is controlled by the control
inputs,
INC
, U/
D
and
CS
.
R
L
: Low End Potentiometer Terminal
R
L
is the low end terminal of the potentiometer. It is not
required that this terminal be connected to a potential
less than the R
H
terminal. Voltage applied to the R
L
terminal cannot exceed the supply voltage, V
CC
or go
below ground, GND. R
L
and R
H
are electrically
interchangeable.
CS
: Chip Select
The chip select input is used to activate the control input
PIN FUNCTIONS
Pin Name
Function
INC
Increment Control
U/
D
Up/Down Control
R
H
Potentiometer High Terminal
GND
Ground
R
WB
Buffered Wiper Terminal
R
L
Potentiometer Low Terminal
CS
Chip Select
V
CC
Supply Voltage
PIN CONFIGURATION
PDIP Package (P, L)
TSSOP Package (U, Y)
MSOP Package (R, Z)
INC
U
/D
V
CC
CS
RL
RWB
GND
RH
1
2
3
4
8
7
6
5
CS
RL
RWB
INC
U
/D
RH
GND
V
CC
1
2
3
4
8
7
6
5
V
CC
CS
RL
RWB
GND
RH
INC
U/
D
1
2
3
4
8
7
6
5
CS
RL
RWB
INC
U
/D
RH
GND
V
CC
1
2
3
4
8
7
6
5
SOIC Package (S, V)