[AK4186]
2. The Position Detection for 5-wire Touch Screen
A 5-wire touch panel consists of one transparent resistive layer and a top metal contact area separated by insulating
spacers. The top layer acts only as a voltage measuring probe, the position detection uses the bottom resistive layer that
had metal contacts at the 4 corners. When the top layer is pressed by a pen or stylus, the top layer contacts with the
bottom layer. Then the X and Y coordinates is detected. The 5-wire touch screen works properly even with damages or
scratches on the top layer, therefore the 5-wire touch panel has higher durability than the 4-wire touch panel. Connect
the metal contact of the top layer to the WIPER pin to measure the Y-axis of current position at AIN+. The top right and
top left contacts at the 4 corners are connected to VDD and the bottom right and bottom left contacts connected to VSS.
Then the AK4186 initiates A/D conversion of AIN+ input voltage, and Y-axis position is determined.
Terminal
X-axis
Y-axis
SW
TL
TR
BL
BR
VSS
VDD
VSS
VDD
VDD
VDD
VSS
VSS
Switch
VDD
VSS
Switch
VDD/VSS ON/OFF ON/OFF VDD/VSS
Table 4. Driver SW configuration
VDD
VDD
TR SW ON
BR SW ON
BR
TR
WIPER
VDD
VDD
TL SW ON
TR SW ON
TL
TR
VREF+
ADC
VREF
AIN+
AIN-
VREF+
AIN+
TL
ADC
VREF-
AIN-
WIPER
BL
TL SW ON
BL SW ON
BL SW ON
BR
BL
BR SW ON
a) X-Position Measurement Differential Mode
b) Y-Position Measurement Differential Mode
The Top layer and Bottom layer are connected on the dotted line when the panel is touched.
Detection side
(Top layer)
WIPER
TL
TR
ADC
BL
BR
5-wire Touch Screen Construction
Drive side
(Bottom Layer)
Figure 4. Axis Measurements for 5-wire Touch Screen
MS1068-E-04
-9-
2011/03
AKM [ ASAHI KASEI MICROSYSTEMS ]
