AK4186 Datasheet, PDF (8/33 Pages) Asahi Kasei Microsystems – Low Power Touch Screen Controller with I2C Interface

[AK4186]
Channel Selection
X-axis Measure
Y-axis Measure
Status of Driver Switch
ADC input (ΔAIN) Reference Voltage (ΔVREF)
TL-Driver BR-Driver AIN+
AIN-
VREF+
VREF-
ON
OFF
WIPER
TL
BR
TL
OFF
ON
WIPER
BR
TL
BR
Table 3. Measurement Mode (5-wire)
Ref. Mode
DFR
DFR
■ Position Detection of Touch Screen
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.
VDD
XP-Driver SW ON
X-Plate
XP
Y-Plate
VDD
YP-Driver SW ON
X-Plate
XP
Y-Plate
VREF+
AIN+
ADC
YP
VREF
AIN-
XN
VREF+
AIN+
ADC
YP
VREF-
AIN-
XN
XN-Driver SW ON
YN
YN Touch Screen
YN-Driver SW ON
a) X-Position Measurement Differential Mode
b) Y-Position Measurement Differential Mode
The X-plate and Y-plate are connected on the dotted line when the panel is touched.
X+
X-Plate (Top side)
X-
Y-
Y-Plate (Bottom side)
Y+
c) 4-wire Touch Screen Construction
Figure 3. Axis Measurements for 4-wire Touch Screen
MS1068-E-04
-8-
2011/03