CAT5128 Datasheet, PDF (2/8 Pages) Catalyst Semiconductor – 32-Tap Digital Up/Down Control Potentiometer

CAT5128
PIN CONFIGURATION
SOT-23 8-Lead
U¯¯P 1
8 V_CC
¯D¯O¯W¯¯N¯
2
7
CAT
NC
A3
6B
GND 4
5W
PIN DESCRIPTIONS
Name Function
U¯¯P Step-Up Control
¯D¯O¯W¯¯N¯ Step-Down Control
A Potentiometer High Terminal
GND Ground
W Wiper Terminal
B Potentiometer Low Terminal
NC Not Connected
V_CC Supply Voltage
PIN DESCRIPTION
U¯¯P: Step-Up Control Input
When ^{¯D¯O¯W¯¯N¯} input is high, a high-to-low transition on
U¯¯P input will cause the wiper to move one increment
toward the A terminal.
¯D¯O¯W¯¯N¯: _{Step-Down Control Input}
A high-to-low transition on ^{¯D¯O¯W¯¯N¯} input will cause the
wiper to move one increment towards the B terminal.
A: High End Potentiometer Terminal
A is the high end terminal of the potentiometer. It is
not required that this terminal be connected to a
potential greater than the B terminal. Voltage applied
to the A terminal cannot exceed the supply voltage,
V_CC or go below ground, GND.
W: Wiper Potentiometer Terminal
W is the wiper terminal of the potentiometer. Its
position on the resistor array is controlled by the
control inputs, U¯¯P and ^{¯D¯O¯W¯¯N¯.} Voltage applied to the
W terminal cannot exceed the supply voltage, V_CC or
go below ground, GND.
B: Low End Potentiometer Terminal
B is the low end terminal of the potentiometer. It is not
required that this terminal be connected to a potential
less than the A terminal. Voltage applied to the B
terminal cannot exceed the supply voltage, V_CC or go
below ground, GND. B and A are electrically
interchangeable.
DEVICE OPERATION
The CAT5128 operates like a digitally controlled
potentiometer with A and B equivalent to the high and
low terminals and W equivalent to the mechanical
potentiometer's wiper. There are 32 available tap
positions including the resistor end points, A and B.
There are 31 resistor elements connected in series
between the A and B terminals. The wiper terminal is
connected to one of the 32 taps and controlled by two
inputs, U¯¯P and ^{¯D¯O¯W¯¯N¯.} These inputs control a five-bit
up/down counter whose output is decoded to select
the wiper position.
A high-to-low transition on ^{¯D¯O¯W¯¯N¯} input will
decrement one step the wiper position (R_WB will
decrease with 1LSB and R_WA will increase with 1LSB).
If and only if ^{¯D¯O¯W¯¯N¯} input is high, a high-to-low
transition on U¯¯P input will increment one step the
wiper position (R_WB will increase with 1LSB and R_WA
will decrease with 1LSB).
The wiper, when at either fixed terminal, acts like its
mechanical equivalent and does not move beyond the
last position. When the CAT5128 is powered-down,
the wiper position is reset. When power is restored,
the counter is set to the mid point, tap 15.
Doc. No. MD-2128 Rev. A
2
© Catalyst Semiconductor, Inc.
Characteristics subject to change without notice