AK4186 AKM [Asahi Kasei Microsystems], AK4186 Datasheet - Page 8

• Manufacturer Part Number: AK4186
• Description: Low Power Touch Screen Controller with I2C Interface
• 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.
MS1068-E-04
ADC
Position Detection of Touch Screen
Channel Selection
X-axis Measure
Y-axis Measure
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
TL-Driver
Status of Driver Switch
X-
OFF
ON
Y-
Figure 3. Axis Measurements for 4-wire Touch Screen
X+
XP
YP
XN
YN
BR-Driver
c)
Table 3. Measurement Mode (5-wire)
OFF
ON
4-wire Touch Screen Construction
X-Plate
Y-Plate
WIPER
WIPER
ADC input (ΔAIN)
AIN+
- 8 -
Y+
ADC
b)
VREF+
VREF-
AIN-
BR
TL
YN-Driver SW ON
Y -Position Measurement Differential Mode
YP-Driver SW ON
Reference Voltage (ΔVREF)
X-Plate (Top side)
Y-Plate (Bottom side)
AIN+
AIN-
VREF+
BR
TL
VDD
VREF-
BR
TL
YP
XN
YN
XP
Touch Screen
X-Plate
Ref. Mode
[AK4186]
Y-Plate
DFR
DFR
2011/03