DS41393A-Page 6

© 2009 Microchip Technology, Inc.

7.5

5-wire Touch Sensor Interface

Sensor tail pin-outs can vary by manufacturer and part number. Ensure sensor tail pins for one pair of diagonally

related sensor corners are connected to the controller’s X–/X+ pins and the tail pins for the other pair of diagonally

related corners are connected to the controller’s Y–/Y+ pins. The controller’s X–/X+ and Y–/Y+ pin pairs do not

need to connect to a specific sensor axis. The orientation of controller pins X– and X+ to the two selected

diagonal sensor corners is not important. Likewise, the orientation of controller pins Y– and Y+ to the other two

selected diagonal sensor corners is not important. The sensor tail pin connected to its topsheet must be

connected to the controller’s 5WSX– pin.

Connections to a 5-wire touch sensor are as follows.

Figure 5 : 5-wire Touch Sensor Interface

Tie unused controller pins SX-, SY-, and SY+ to VSS.

The capacitance of alternate ESD diodes may adversely affect touch performance. A lower

capacitance is better. The PESD5V0S1BA parts shown in the reference design have a typical

capacitance of 35pF. Test to ensure that selected ESD protection does not degrade touch

performance.

ESD protection is shown in the reference design, but acceptable protection is dependent on your

specific application. Ensure your ESD solution meets your design requirements.