DS1802

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101999

DESCRIPTION

The DS1802 is a dual audio taper-potentiometer having logarithmic resistive characteristics over the

device range. Each potentiometer provides 65 wiper positions with a 1 dB increment per step and device

mute. The DS1802 has two methods of device control, which include contact closure (pushbutton) inputs

and a 3-wire serial interface for wiper positioning. The pushbutton control inputs provide a simple

interface for device control without the need for a CPU. While the 3-wire serial interface, using a CPU,

provides the user the ability of reading or writing exact wiper positions of the two potentiometers. The

DS1802 can also be configured to operate in either independent or “stereo” modes when using pushbutton

control. Independent mode of operation allows for independent wiper control, and stereo mode of

operation provides single input control over both potentiometer wiper positions. The DS1802 is offered in

commercial temperature versions. Packages for the part include a 20-pin DIP, 20-pin SOIC, and 20-pin

TSSOP.

OPERATION

The DS1802 provides two 65-position potentiometers per package, each having a logarithmic resistive

characteristic as shown in Table 1. The DS1802 can be controlled either digitally or mechanically using a

3-wire serial interface or contact closure input, respectively. The pushbutton interface allows for a simple

mechanical control method for incrementing or decrementing wiper position. The 3-wire serial interface

is designed for CPU controlled applications and allows the potentiometer’s exact wiper position to be

read or written. Additionally, the DS1802 can be daisy-chained for multi-device environments.

Figure 1 presents a block diagram of the DS1802. As shown, the inputs from the 3-wire serial interface

and contact closure inputs drive a command/control unit. The command/control unit interprets these

inputs for control of the two potentiometers.

The MODE input is used for contact closure operation. This input allows the user to choose between

independent mode control and stereo mode control. The MODE input is discussed in detail under the

contact closure interface control.

On power-up the serial port is stable and active within 10 microseconds. The contact closure control

interface inputs are active after 50 ms. The wiper position on power-up will be at position 63, the low end

of the potentiometer. Position 64 is the mute level.

RESISTANCE CHARACTERISTICS Table 1

POSITION

OUTPUT LEVEL (dB)

0

0

1

-1

2

-2

3

-3

4

-4

5

-5

•

•

•

•

•

•

63

-63

64(mute)

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