AK4186 Datasheet, PDF (9/33 Pages) Asahi Kasei Microsystems – Low Power Touch Screen Controller with I2C Interface

[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
TR SW ON
VDD
BR SW ON
VREF+
ADC
VREF
AIN+
AIN-
BR
TR
WIPER
TL
BL SW ON
TL SW ON
BL
VDD
TR SW ON
VDD
TL SW ON
VREF+
AIN+
ADC
VREF-
AIN-
BL SW ON
BR SW ON
TL
TR
WIPER
BL
BR
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) _ADC
WIPER
TL
TR
BL
BR
Drive side (Bottom Layer)
5-wire Touch Screen Construction
Figure 4. Axis Measurements for 5-wire Touch Screen
MS1068-E-04
-9-
2011/03