CAT5112
Doc. No. MD-2002 Rev. N 2 © 2008 SCILLC. All rights reserved.
Characteristics subject to change without notice
PIN CONFIGURATION
PDIP 8-Lead (L)
SOIC 8 Lead (V)
MSOP 8 Lead (Z)
INC
¯¯¯
1
8
V
CC
U/D
¯
2
7
CS
¯¯
R
H
3
6
R
L
GND
4
5
R
WB
CAT
TSSOP 8 Lead (Y)
CS
¯¯
1
8
R
L
V
CC
2
7
R
WB
INC
¯¯¯
3
6
GND
U/D
¯
4
5
R
H
CAT
PIN DESCRIPTIONS
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 DESCRIPTION
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 potentio–
meter. 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 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 mecha–
nical potentiometer's wiper. There are 32 available tap
positions 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 deselected
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 non-
volatile memory.
