AK4180 Datasheet, PDF (9/17 Pages) Asahi Kasei Microsystems – Touch Screen Controller

[ASAHI KASEI]
[AK4180]
ON
YP
ON
YP
XP
VREF+
AIN+
ADC
VREF-
AIN-
XN
ON
YN
touch
XP
VREF+
AIN+
ADC
VREF-
AIN-
XN
ON
YN
touch
b) Z1-Position Measurement
Differential Mode
a) Z2-Position Measurement
Differential Mode
Figure 2 Pen Pressure Measurement
„ Voltage Reference
The AK4180 has an internal 2.5V voltage reference. This reference can be turned ON when PD1 = “1”, and OFF when PD1 = “0”.
This reference is used in the single-ended mode for the battery monitoring, temperature measurement, or for auxiliary input. A
0.1µF or larger capacitor should be connected for stable operation of the VREF circuit. Setting time depends on this external
capacitance, but 400µs or longer time is required if the external capacitance is 0.1µF.
If an external voltage reference is used, PD1 bit should be set to “0”.
„ Battery Measurement
The AK4180 can measure the battery voltage that is up to 5V directly while the AK4180 operates at 2.7V or 3.3V, etc. The input
voltage is internally divided down by 4. Minimum 5µs is required as tracking time. If the source impedance is large, more
tracking time is required.
VBAT
R0
R1=7.5K
R2=2.5K
Internal
PD1
VREF
AIN+
VREF+
ADC
AIN-
VREF-
Enable
Figure 3 Battery Monitoring
<MS0195-E-01>
9
2003/02