ASAHI KASEI
[AK4181A]
MS0313-E-00
2004/06
1
AK4181A
Touch Screen Controller
AIN+
AIN-
Internal VREF(2.5V)
12bit
ADC
(SAR type)
VREF+
VREF-
YN
XN
YP
XP
VBAT
VREF
DCLK
CSN
DIN
DOUT
IN1
BUSY
PENIRQN
VCC
GND
Control
Logic
IN2
Temp.
Sensor
R1
R2
PEN
INTERRUPT
Block Diagram
Features:
Sampling Frequency: 125kHz(max)
Pen Pressure Measurement
On-Chip Thermo Sensor
Two Auxiliary Analog Inputs
Direct Battery Measurement
4-wire I/F
On-Chip Voltage Reference (2.5V)
12 bit SAR type A/D Converter with S/H circuit
Low Power Consumption (250
A)
Low Voltage Operation (2.7V - 3.6V)
Package 16pin
TSSOP
General Description:
The AK4181A is a 4-wire touch screen controller that
incorporates a 12-bit 125kHz sampling SAR A/D converter.
The AK4181A can detect the pressed screen location by
performing two A/D conversions. In addition to location, the
AK4181A also measures touch screen pressure.
On-chip VREF can be utilized for two analog auxiliary
inputs and battery monitoring, with the ability to measure
voltages from 0V to 5V.
The AK4181A also has an on-chip temperature sensor.
ASAHI KASEI
[AK4181A]
MS0313-E-00
2004/06
2
Ordering Guide
AK4181AVT -20
C +70C
16pinTSSOP
Pin Layout
Top View
6
5
4
3
2
1
VCC
XP
XN
YP
YN
GND
VBAT 7
IN1 8
11
12
13
14
15
16
DCLK
CSN
DIN
BUSY
DOUT
PENIRQN
10
IN2
9
VREF
ASAHI KASEI
[AK4181A]
MS0313-E-00
2004/06
3
Pin/Function
No. Signal
Name I/O
Description
1 VCC
- Power
Supply
2
XP
I/O
Touch Screen X+ plate Voltage supply
X axis Measurement: Supplies the voltage to X+ position input
Y axis Measurement: This pin is used as the input for the A/D converter
Pen Pressure Measurement: This pin is the input for the A/D converter at Z1 measurement.
Temperature/VBAT/IN1/IN2 Measurement: OPEN state
Pen Waiting State: Pulled up by an internal resistor (typ.50k ohm).
3
YP
I/O
Touch Screen Y+ plate Voltage supply
Y axis Measurement: Supplies the voltage to Y+ position input
X axis Measurement: This pin is used as the input for the A/D converter
Pen Pressure Measurement: Supplies the voltage.
Temperature/VBAT/IN1/IN2 Measurement: OPEN state
4
XN
I/O
Touch Screen X- plate Voltage supply
X axis Measurement: Supplies the voltage to X- position input
Y axis Measurement: OPEN state
Pen Pressure Measurement: Supplies the voltage.
Temperature/VBAT/IN1/IN2 Measurement: OPEN state
5
YN
I/O
Touch Screen Y- plate Voltage supply
Y axis Measurement: Supplies the voltage to Y- position input
X axis Measurement: OPEN state
Pen Pressure Measurement: This pin is the input for the A/D converter at Z2 measurement.
Temperature/VBAT/IN1/IN2 Measurement: OPEN state
Pen Waiting State: connected to GND.
6 GND
- Ground
7
VBAT
I
Analog Input for Battery Monitor
8
IN1
I
Auxiliary 1 Analog Input
9
VREF
I/O
Voltage Reference Input/Output
Outputs 2.5V
10
IN2
I
Auxiliary 2 Analog Input
11
PENIRQN
O
Pen Interrupt Output
This pin should be pulled up via a 100k-ohm resistor. This pin is "L" during the pen down on
pen interrupt enable state with CSN ="H" otherwise this pin is "H". This pin is "H" during pen
interrupt disable state with the CSN = "H" regardless pen touch. See Power-down Control and
Pen Interrupt for the reference.
12
DOUT
O
Serial A/D Data Output
Output A/D data serially at the falling edge of DCLK. MSB is output at the falling edge of
BUSY signal.
Output "L" at CSN= "L" during A/D data does not output.
This pin is Hi-Z state at CSN="H"
13 BUSY
O BUSY
Output
This pin goes to low at CSN = "L". BUSY signal is "H" only for the period between the falling
edge of 8
th
DCLK and the falling edge of 9
th
DCLK.
This pin is Hi-Z state at CSN= "H"
14 DIN
I Serial
Data
Input
Inputs 8-bit control command data serially when CSN= "L"
AK4181A latches at the rising edge of DCLK. Must keep "L" while not issuing commands.
15 CSN
I Chip
Select
Input
Enables writing data to the registers when CSN= "L".
16 DCLK
I External
Clock
Input
ASAHI KASEI
[AK4181A]
MS0313-E-00
2004/06
4
Absolute Maximum Ratings
GND=0V (Note 1)
Parameter Symbol
Min
max
Units
Power Supplies
VCC
-0.3
6.0
V
Input Current (any pins except for supplies)
IIN
-
10
mA
Input Voltage
VIN
-0.3
6.0(VCC+0.3)
V
Touch Panel Drive Current IOUTDRV
50
mA
Ambient Temperature (power supplied)
Ta
-20
70
C
Storage Temperature
Tstg
-65
150
C
Note 1.All voltages with respect to ground.
WARNING: Operation at or beyond these limits may result in permanent damage to the device.
Normal operation is not guaranteed at these extremes.
Recommended Operating Conditions
GND=0V (Note 1)
Parameter
Symbol
Min
typ
max
Units
Power Supplies
VCC
2.7
3.3
3.6
V
Note 1. All voltages with respect to ground.
WARNING: AKM assumes no responsibility for the usage beyond the conditions in this datasheet.
ASAHI KASEI
[AK4181A]
MS0313-E-00
2004/06
5
Analog Characteristics
Ta=-20
C to 70C, VCC=2.7V, External Vref =2.5V, fs=125kHz, fDCLK=16*fs, 12bit mode
Parameter min
typ
max
Units
ADC for Touch Screen
Resolution
12
Bits
No Missing Codes
11
12
Bits
Integral Linearity Error
2
LSB
DNL
1
LSB
Analog Input Voltage Range
0
Vref
V
Offset Error
6
LSB
Gain Error
4
LSB
Touch Panel Driver
XP, YP, RL=300
XN, YN, RL=300
5
5
XP Pull Up Register (when pen interrupt enable)
50
K
PSRR (10KHz 100mVpp)
70
dB
Reference Output
Internal Reference
2.45 2.50 2.55 V
Drift
30
ppm/
C
Load Capacitance
0.1
F
Reference Input
Input Voltage Range
VCC
V
Battery Monitor
Input Voltage Range
5.0
V
Input Impedance (Battery Measure Mode)
5
10
K
Accuracy (Note 2) External VREF = 2.5V is used
2
%
Accuracy (Note 2) Internal Reference is used.
3
%
Temperature Measurement
Temperature Range
-20
70
C
Resolution (Note 3)
1.6
C
Accuracy (Note 4)
3
C
Power Supply Current
Normal Mode (Internal Reference OFF)
250
500
A
Normal Mode (Internal Reference ON)
520
800
A
Full Power Down(when writing control command with PD1=PD0= "0")
0
3
A
Note 2. Accuracy is the difference between the output code when 5 volts is input to the VBAT pin and the "ideal" code at 1.25
volts.
Note 3. "ideal" value derived from theory
Note 4. Accuracy is defined as the difference between the voltage measured by two current sources, and the ideal voltage derived
from theory at specific temperatures.
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