CAT5110_07 Datasheet, PDF (5/16 Pages) Catalyst Semiconductor – 32-Tap MiniPot™ Digitally Programmable Potentiometers with 2-Wire Interface

CAT5110, CAT5118, CAT5119, CAT5123, CAT5124, CAT5125
Functional Description
The CAT5110/5118/5119/5123/5124/5125 consist of
a fixed resistor and a wiper contact with 32-tap points
that are digitally controlled through a 2-wire up/down
serial interface. Three end-to-end resistance values are
available: 10kΩ, 50kΩ and 100kΩ.
The CAT5110/5125 is designed to operate as a
potentiometer. In this configuration, the low terminal of
the resistor array is connected to ground (pin 2).
The CAT5118/5123 performs as a variable resistor. In
this device, the wiper terminal and high terminal of the
resistor array are connected at pin 5. The CAT5119/5124
is a similar variable resistor, except the low terminal is
connected to pin 5.
Digital Interface Operation
The MiniPots have two modes of operation when the
serial interface is active: increment and decrement mode.
The serial interface is only active when CS is low.
The CS and U/D inputs control the position of the wiper
along the resistor array. When CS transitions from high
to low, the part will go into increment mode if U/D input
is high, and into decrement mode when U/D input is low.
Once the mode is set, the device will remain in that mode
until CS goes high again. A low-to-high transition at the
U/D pin will increment or decrement the wiper position
depending on the current mode (Figures 1 and 2).
When the CS input transitions to high (serial interface
inactive), the value of the counter is stored and the wiper
position is maintained.
Note that when the wiper reaches the maximum (or
minimum) tap position, the wiper will not wrap around
to the minimum (or maximum) position.
Power-On Reset
All parts in this family feature power-on reset (POR)
circuitry that sets the wiper position to midscale at power-
up. By default, the chip is in the increment mode.
Figure 1. Serial Interface Timing Diagram, Increment Mode
CS
t _CU
U/D
W
t _IL
t _CI
t _IH
t _SETTLE
Note: "W" is not a digital signal. It represents wiper transitions.
t _IC
t _SETTLE
Figure 2. Serial Interface Timing Diagram, Decrement Mode
CS
t _CU
t _IH
U/D
t _IL
t _CI
W
t _SETTLE
Note: "W" is not a digital signal. It represents wiper transitions.
t _IC
t _SETTLE
© Catalyst Semiconductor, Inc.

Characteristics subject to change without notice
Doc No. MD-2120, Rev. F