DS1802 Datasheet, PDF (2/17 Pages) Dallas Semiconductor – Dual Audio Taper Potentiometer With Pushbutton Control

DS1802
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)
<-90
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