DS1806

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102199

For multiple device and single processor environments, the DS1806 can be cascaded or daisy-chained.

This feature allows a single processor to control multiple devices.

The DS1806 is available in 10, 50 and 100-kohm versions and is specified over the industrial temperature

range. Packages for the device include 20-lead DIPs, SOICs, and TSSOPs.

OPERATION

A block diagram of the device is provided in Figure 1. As shown, the DS1806 contains six 64-position

potentiometers whose wiper positions are set by an 8-bit value. The DS1806 contains a 48-bit I/O shift

register which is used to store the respective wiper position data for each of the six potentiometers.

same low-end terminal L1-3. And likewise, potentiometers 4 through 6 share the low-end terminal L4-6.

Control of the DS1806 is accomplished via a 3-wire serial communication interface which allows the user

to set the wiper position value for each potentiometer. The 3-wire serial interface consists of the control

is active when in a high state. Any communication intended to change wiper settings must begin with the

The CLK signal input is used to provide timing synchronization for data input and output. Wiper position

the 48-bit I/O shift register of the part, LSB first. Figure 3 provides an illustration of the 48-bit shift

register.

Figure 4 provides 3-wire serial port protocol and timing diagrams. As shown, the 3-wire port is inactive

port becomes active. When active, data is loaded into the I/O shift register on the low-to-high transition of

the CLK.

Data is transmitted in order of LSB first. Potentiometers are designated from 1 through 6 and the value

for potentiometer-1 will be the first data entered into the shift register, followed by that of potentiometer-

2 and so forth.

Each wiper has an 8-bit register which is used for setting the position of the wiper on the resistor array.

Because the DS1806 is a 64-position potentiometer, only six bits of information are needed to set wiper

position. The remaining two bits of information are used to provide a “don’t change” feature. Wiper

position is controlled by bit positions 0 through 5 of each register. The “don’t change” feature is

controlled by bits 6 and 7 of each register. When bits 6 and 7 have value “11 xxxxxx,” wiper position will

not change regardless of the states of bits 0 through 5. If bits 6 and 7 are set to any other value, bits 0

through 5 will be used as the new wiper position. The “don’t change” feature allows the user to change

the value of any potentiometer of the DS1806 without affecting or having to remember the remaining

positions of the potentiometer wipers. Figure 2 provides the format for a wiper’s register.