CAT5127_0708 Datasheet, PDF (3/13 Pages) Catalyst Semiconductor – 32-Tap Digitally Programmable Potentiometer (DPP™)

CAT5127, CAT5129
DEVICE OPERATION
The CAT5127 operates like a digitally controlled
variable resistor with R_H and R_L equivalent to the high
and low terminals. 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 CAT5129 operates like a digitally controlled
variable resistor with R_H equivalent to the high
terminal. There are 32 available tap positions
including the resistor end points, R_H and GND. There
are 31 resistor elements connected in series between
the R_H and GND terminals.
Operation is controlled by three inputs, I¯N¯C¯, U/D¯ and
C¯¯S. 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 I¯N¯C¯ and C¯¯S inputs.
With C¯¯S set LOW, the device is selected and will
respond to the U/D¯ and I¯N¯C¯ inputs. HIGH to LOW
transitions on I¯N¯C¯ wil increment or decrement the
wiper (depending on the state of the U/D¯ input and
five-bit counter). The wiper, when at either end
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 C¯¯S
transitions HIGH while the I¯N¯C¯ input is also HIGH.
When the device 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 I¯N¯C¯ set low, the device 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.
OPERATION MODES
I¯N¯C¯
C¯¯S
High to Low
Low
High to Low
Low
High
Low to High
Low
Low to High
X
High
U/D¯
High
Low
X
X
X
Operation
Wiper toward H
Wiper toward L/GND
Store Wiper Position
No Store, Return to Standby
Standby
R_H
C_H
C_L
R_L/GND
Variable Resistor Equivalent Circuit
© Catalyst Semiconductor, Inc.
3
Characteristics subject to change without notice
Doc. No. MD-2127 Rev. C