DS41393A-Page 26

© 2009 Microchip Technology, Inc.

8.3

4-Wire Sensor

A 4-wire resistive touch sensor consists of a Stable and Flex layer, electrically separated by spacer dots. The

layers are assembled perpendicular to each other. The touch position is determined by first applying a voltage

gradient across the flex layer and using the stable layer to measure the flex layer’s touch position voltage. The

second step is applying a voltage gradient across the stable layer and using the flex layer to measure the stable

layer’s touch position voltage.

The measured voltage at any position across a driven axis is predictable. A touch moving in the direction of the

driven axis will yield a linearly changing voltage. A touch moving perpendicular to the driven axis will yield a

relatively unchanging voltage.

Figure 14: 4-Wire Decoding