ak4184a AKM Semiconductor, Inc., ak4184a Datasheet - Page 10

• Manufacturer Part Number: ak4184a
• Description: Tsc With Keypad Scanner And Gpio Expander
• Manufacturer: AKM Semiconductor, Inc.

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XY-coordinate detection (XY-position) from the touch panel is determined by the control command (A1, A0) bits of
the touch screen control command. Coordinate detection is in differential mode. The full scale (ΔVREF) is the
differential voltage between the non-inverting terminal and the inverting terminal of the measured axis (e.g. X-axis
measurement: ΔVREF = V
terminal (V
) = V
into the internal capacitors after the capacitor has been fully charged. The required settling time to charge the internal
capacitor array needs at least 1.5μs. The maximum throughput of the A/D converter is 125kHz. The position from 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-dimensional (X/Y axis) position.
MS0947-E-00
Touch Screen Position Detection
YP
– V
ADC
XP
XN
) of the non-target axis and the inverting terminal (V
) The input voltage charges the internal capacitor during the sampling time period. No current flows
a) X-Position Measurement Differential Mode
VREF+
VREF-
XN-Driver SW ON
XP-Driver SW ON
The X-Plate and Y-plate are connected on the dotted line when the panel is touched.
AIN+
AIN-
XP
AVDD
– V
XN
XN
YN
). The input (ΔAIN) of the A/D converter is the voltage between the non-inverting
XP
XP
YP
XN
YN
Figure 4. Axis Measurement
c) 4-wire Touch Screen
X-Plate
Y-Plate
- 10 -
YP
ADC
XN
b) Y-Position Measurement Differential Mode
VREF+
VREF-
) of the target axis. (E.g. ΔAIN = (AIN+) - (AIN-
YN-Driver SW ON
YP-Driver SW ON
X-Plate (Top side)
Y-Plate (Bottom side)
AIN+
AIN-
AVDD
XP
YP
XN
YN
Touch Screen
X-Plate
Y-Plate
[AK4184A]
2008/04