AR1000 Datasheet, PDF (9/37 Pages) Microchip Technology – Resistive Touch Screen Controller

7.3 4, 5, 8-Wire Sensor Selection
The desired sensor type of 4/8-Wire or 5-Wire is hardware selectable using pin M2.
Type
4/8-wire
5-wire
M2 pin
VSS
VDD
Table 4 : 4/8-wire vs 5-wire Selection
If 4/8-wire has been hardware selected, then the choice of 4-wire or 8-wire is software selectable, via the
TouchOptions configuration register. When 4/8-Wire is hardware selected, the controller defaults to 4-wire
operation. If 8-wire operation is desired, then the TouchOptions configuration register must be changed.
7.4 4-wire Touch Sensor Interface
Sensor tail pin-outs can vary by manufacturer and part number. Ensure both sensor tail pins for one sensor axis
(layer) are connected to the controller’s X–/X+ pins and the tail pins for the other sensor axis (layer) 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 sides of a given sensor axis is not
important. Likewise, the orientation of controller pins Y– and Y+ to the two sides of the other sensor axis is not
important.
Connections to a 4-wire touch sensor are as follows.
Figure 4 : 4-wire Touch Sensor Interface
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.
Tie unused controller pins 5WSX-, SX+, SY-, and SY+ to VSS.
© 2009 Microchip Technology, Inc.
DS41393A-Page 5