AK4185 AKM [Asahi Kasei Microsystems], AK4185 Datasheet - Page 9

• Manufacturer Part Number: AK4185
• Manufacturer: AKM [Asahi Kasei Microsystems]

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, which connected inside of the AK4185, to AIN+ to measure the Y-axis of
current position. 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 AK4185 initiates A/D conversion of AIN+ input voltage, and Y-axis position is
determined.
MS0954-E-00
TR SW ON
VREF+
VREF
The Top layer and Bottom layer are connected on the dotted line when the panel is touched.
VDD
BL SW ON
a) X-Position Measurement Differential Mode
ADC
BL
AIN+
AIN-
BR SW ON
TL SW ON
VDD
5-wire Touch Screen Construction
Terminal
TL
X-axis
Y-axis
Figure 4. Axis Measurements for 5-wire Touch Screen
SW
WIPER
TL
BR
TR
BL
VDD/VSS
Table 2. Driver SW configuration
Switch
VDD
VSS
TL
BR
ON/OFF
VDD
VDD
VDD
- 9 -
TR
TR SW ON
Detection side
ON/OFF
VREF+
VREF-
VSS
VSS
VSS
BL
Drive side
VDD
TR
BL SW ON
b) Y-Position Measurement Differential Mode
ADC
WIPER
VDD/VSS
TL SW ON
AIN+
AIN-
Switch
VDD
(Top layer)
(Bottom Layer)
VSS
BR
BR SW ON
VDD
ADC
WIPER
TR
TL
BL
BR
[AK4185]
2008/05