AK4185 AKM [Asahi Kasei Microsystems], AK4185 Datasheet - Page 8

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

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1. The Position Detection for 4-wire Touch Screen
The position on the touch screen is detected by taking the voltage of one axis when the voltage is supplied between the two
terminals of another axis. At least two A/D conversions are needed to get the two-dimensions (X/Y-axis) position.
MS0954-E-00
ADC
Position Detection of Touch Screen
a)
VREF+
VREF
XN-Driver SW ON
XP-Driver SW ON
X-Position Measurement Differential Mode
The X-plate and Y-plate are connected on the dotted line when the panel is touched.
AIN+
AIN-
VDD
X-
Y-
Figure 3. Axis Measurements for 4-wire Touch Screen
X+
YP
XN
YN
XP
c)
4-wire Touch Screen Construction
X-Plate
Y-Plate
- 8 -
Y+
ADC
b)
VREF+
VREF-
Y-Position Measurement Differential Mode
YP-Driver SW ON
YN-Driver SW ON
X-Plate (Top side)
Y-Plate (Bottom side)
AIN+
AIN-
VDD
YP
XN
YN
XP
Touch Screen
X-Plate
[AK4185]
Y-Plate
2008/05