ak4181a AKM Semiconductor, Inc., ak4181a Datasheet - Page 9

• Manufacturer Part Number: ak4181a
• Description: Touch Screen Controller
• Manufacturer: AKM Semiconductor, Inc.

ASAHI KASEI
The AK4181A 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. Settling 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”.
The AK4181A can directly measure the battery voltage up to 5V while the AK4181A operates at 2.7V to 3.3V. The input voltage
is internally divided down by 4 and applied to the input of AD converter (AIN+). Minimum 5µs is required as tracking time. If
the source impedance is larger, more tracking time is required.
MS0313-E-00
ADC
Voltage Reference
Battery Measurement
VREF+
VREF-
a)
Z1-Position Measurement Differential Mode
ON
ON
AIN+
AIN-
VBAT
R0
YP
XP
XN
YN
R2=2.5K
R1=7.5K
Figure 3 Pen Pressure Measurements
Figure 4 Battery Monitoring
touch
Enable
9
VREF(2.5V)
ADC
Internal
VREF+
VREF-
b)
ON
ON
AIN+
AIN-
Z2-Position Measurement Differential Mode
PD1
ADC
AIN+
AIN-
VREF+
VREF-
VREF
YP
XP
XN
YN
touch
[AK4181A]
2004/06