WMS7170 / 7171

Publication Release Date: July 2003

- 7 -

Revision 1.0

7. FUNCTIONAL DESCRIPTION

The WMS7170 device can operate as either a two-terminal variable resistor or a three-terminal

voltage divider without an output buffer. However, the WMS7171 can only operate in a three-terminal

voltage divider with an output buffer.

7.1.1. Rheostat Configuration

In the rheostat mode, the WMS7170 can be configured as a two-terminal resistive element, where one

The moving direction of the wiper depends upon the setting of U/ D control signal. When the U/ D is

signal from HIGH to LOW.

This configuration controls the resistance between the wiper and either end. The wiper resistance can

be adjusted by either changing the wiper position or loading a stored wiper position value from

NVMEM0 upon power up.

7.1.2. Divider Configuration

Additionally, the WMS7170 can also be configured as a voltage divider. With an input voltage applied

the wiper depends upon the setting of the U/ D control signal. When the U/ D is set to Up, then the

LOW.

Nevertheless, the WMS7171 can only be configured as a voltage divider and operate similarly as the

WMS7170 device. The only difference is WMS7171 has an output buffer, but WMS7170 doesn’t have.

Besides, the resistance cannot be directly measured in this configuration.

The WMS7170/7171 has one NVMEM0 location available for storing the current wiper position via the

Up/Down serial interface. This stored value is automatically recalled and loaded into the tap register

upon power up.