CAT5121 CATALYST [Catalyst Semiconductor], CAT5121 Datasheet - Page 7

• Manufacturer Part Number: CAT5121
• Description: 16-Tap MiniPot Digitally Programmable Potentiometers with 2-Wire Interface
• Manufacturer: CATALYST [Catalyst Semiconductor]

The CAT5120/5121/5122 consist of a fixed resistor and
a wiper contact with 16-tap points that are digitally
controlled through a 2-wire up/down serial interface.
Three end-to-end resistance values are available: 10k ,
50k and 100k .
The CAT5120 is designed to operate as a potentiometer.
In this configuration, the low terminal of the resistor array
is connected to ground (pin 2).
The CAT5122 performs as a variable resistor. In this
device, the wiper terminal and high terminal of the
resistor array is connected at pin 5. The CAT5121 is a
similar variable resistor, except the low terminal is
connected to pin 5.
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.
CS
U/D
W
Note: "W" is not a digital signal. It represents wiper transitions.
CS
U/D
W
Note: "W" is not a digital signal. It represents wiper transitions.
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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.
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.
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Doc. No. 2121, Rev. A
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