CAT5111
2
Doc. No. 2008, Rev. M
of the CAT5111 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 CAT5111 operates like a digitally controlled
potentiometer with RH and RL equivalent to the high
and low terminals and RWB equivalent to the mechanical
potentiometer's wiper. There are 100 available tap
positions including the resistor end points, RH and RL.
There are 99 resistor elements connected in series
between the RH and RL terminals. The wiper terminal is
connected to one of the 100 taps and controlled by three
inputs, INC, U/D and CS. These inputs control a seven-
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 CAT5111 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
seven-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 CAT5111 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 CAT5111 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
INCINC
INCINC
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/DD
DD
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 RH 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
RL terminal.
RH: High End Potentiometer Terminal
RH is the high end terminal of the potentiometer. It is not
required that this terminal be connected to a potential
greater than the RL terminal. Voltage applied to the RH
terminal cannot exceed the supply voltage, VCC or go
below ground, GND.
RWB: Wiper Potentiometer Terminal (Buffered)
RWB 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.
RL: Low End Potentiometer Terminal
RL is the low end terminal of the potentiometer. It is not
required that this terminal be connected to a potential
less than the RH terminal. Voltage applied to the RL
terminal cannot exceed the supply voltage, VCC or go
below ground, GND. RL and RH are electrically
interchangeable.
CSCS
CSCS
CS: Chip Select
The chip select input is used to activate the control input
PIN FUNCTIONS
Pin Name Function
INC Increment Control
U/DUp/Down Control
RHPotentiometer High Terminal
GND Ground
RWB Buffered Wiper Terminal
RLPotentiometer Low Terminal
CS Chip Select
VCC Supply Voltage
PIN CONFIGURATION
PDIP Package (P, L) TSSOP Package (U, Y)
MSOP Package (R, Z)
INC
VCC
CS RL
RWB
U/D RH
GND
1
2
3
4
8
7
6
5
CS
INC V
CC
RL
RWB
U/D
RH
GND
1
2
3
4
8
7
6
5
V
CC
RL
RWB
GND
RH
INC
U/DCS
1
2
3
4
8
7
6
5
CS
INC V
CC
RL
RWB
U/D
RH
GND
1
2
3
4
8
7
6
5
SOIC Package (S, W)