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: 10k , 50k and 100k .

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

¯¯ is low. mode. The serial interface is only active when CS

¯¯ and U/D¯ inputs control the position of the The CS

¯¯ transitions wiper along the resistor array. When CS

from high to low, the part will go into increment mode

¯ input is high, and into decrement mode when if U/D

¯ input is low. Once the mode is set, the device will U/D

¯¯ goes high again. A low-

remain in that mode until CS

¯ pin will increment or to-high transition at the U/D

decrement the wiper position depending on the current mode (Figures 1 and 2).

¯¯ input transitions to high (serial interface When the CS

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

© Catalyst Semiconductor, Inc.

Characteristics subject to change without notice

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Doc. No. MD-2120 Rev. J