CAT5115_13 Datasheet, PDF(2/12 Page) ON Semiconductor – 32‐tap Digital Potentiometer (POT)

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CAT5115_13 Datasheet, PDF (2/12 Pages) ON Semiconductor – 32‐tap Digital Potentiometer (POT)

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CAT5115

Functional Diagram

VCC

U/D

Control

INC

and

PowerâOn

Recall

GND

Figure 1. General

VDD

RH GND

RW INC

U/D

RH/VH

RW/VW

RL/VL

Figure 2. Detailed

Figure 3. Electronic

Potentiometer

Implementation

Table 1. PIN DESCRIPTIONS

Name

Function

INC

Increment Control

U/D

Up/Down Control

GND

Potentiometer High Terminal

Ground

Buffered Wiper Terminal

Potentiometer Low Terminal

Chip Select

VCC

Supply Voltage

Pin Function

INC: Increment Control Input

The INC input moves the wiper in the up or down direction

determined by the condition of the U/D input.

U/D: Up/Down Control Input

The U/D input controls the direction of the wiper movement.

When in a high state and CS is low, any high-to-low

transition on INC will cause the wiper to move one

increment toward the RH terminal. When in a low state and

CS is low, any high-to-low transition on INC will cause the

wiper to move one increment towards the RL terminal.

RH: High End Potentiometer Terminal

RH is the high end terminal of the potentiometer. It is not

required that this terminal be connected to a potential greater

than the RL terminal. Voltage applied to the RH terminal

cannot exceed the supply voltage, VCC or go below ground,

GND.

RW: Wiper Potentiometer Terminal

RW is the wiper terminal of the potentiometer. Its position on

the resistor array is controlled by the control inputs, INC,

U/D and CS. Voltage applied to the RW terminal cannot

exceed the supply voltage, VCC or go below ground, GND.

RL: Low End Potentiometer Terminal

RL is the low end terminal of the potentiometer. It is not

required that this terminal be connected to a potential less

than the RH terminal. Voltage applied to the RL terminal

cannot exceed the supply voltage, VCC or go below ground,

GND. RL and RH are electrically interchangeable.

CS: Chip Select

The chip select input is used to activate the control input of

the CAT5115 and is active low. When in a high state, activity

on the INC and U/D inputs will not affect or change the

position of the wiper.

Device Operation

The CAT5115 operates like a digitally controlled

potentiometer with RH and RL equivalent to the high and low

terminals and RW equivalent to the mechanical

potentiometerâs wiper. There are 32 available tap positions

including the resistor end points, RH and RL. There are 31

resistor elements connected in series between the RH and RL

terminals. The wiper terminal is connected to one of the 32

taps and controlled by three inputs, INC, U/D and CS. These

inputs control a five-bit up/down counter whose output is

decoded to select the wiper position.

With CS set LOW the CAT5115 is selected and will

respond to the U/D and INC inputs. HIGH to LOW

transitions on INC will increment or decrement the wiper

(depending on the state of the U/D input and five-bit

counter). The wiper, when at either fixed terminal, acts like

its mechanical equivalent and does not move beyond the last

position. When the CAT5115 is powered-down, the wiper

position is reset. When power is restored, the counter is set

to the mid point, tap 15.

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