[AK4181A]
AK4181A
Touch Screen Controller
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.
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 (250μA)
Low Voltage Operation (2.7V - 3.6V)
Package
16pin TSSOP
DCLK
XP
CSN
YP
DIN
Control
Logic
XN
YN
DOUT
BUSY
IN1
Internal VREF(2.5V)
VREF
IN2
VBAT
R1
R2
VREF+
AIN+
AIN-
VREF-
12bit
ADC
(SAR type)
PENIRQN
PEN
INTERRUPT
Temp.
Sensor
VCC
GND
Block Diagram
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[AK4181A]
Ordering Guide
AK4181AVT
-20°C ∼ +70°C
16pinTSSOP
Pin Layout
MS0313-E-02
VCC
1
16
DCLK
XP
2
15
CSN
YP
3
14
DIN
XN
4
13
BUSY
YN
5
12
DOUT
GND
6
11
PENIRQN
VBAT
7
10
IN2
IN1
8
9
Top View
2
VREF
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[AK4181A]
Pin/Function
No.
1
2
Signal Name
VCC
XP
I/O
I/O
3
YP
I/O
4
XN
I/O
5
YN
I/O
6
7
8
9
GND
VBAT
IN1
VREF
I
I
I/O
10
11
IN2
PENIRQN
I
O
12
DOUT
O
13
BUSY
O
14
DIN
I
15
CSN
I
16
DCLK
I
MS0313-E-02
Description
Power Supply
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).
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
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
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.
Ground
Analog Input for Battery Monitor
Auxiliary 1 Analog Input
Voltage Reference Input/Output
Outputs 2.5V
Auxiliary 2 Analog Input
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.
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”
BUSY Output
This pin goes to low at CSN = “L”. BUSY signal is “H” only for the period between the falling
edge of 8th DCLK and the falling edge of 9th DCLK.
This pin is Hi-Z state at CSN= “H”
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.
Chip Select Input
Enables writing data to the registers when CSN= “L”.
External Clock Input
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[AK4181A]
Absolute Maximum Ratings
GND=0V (Note 1)
Parameter
Power Supplies
Input Current (any pins except for supplies)
Input Voltage
Touch Panel Drive Current
Ambient Temperature (power supplied)
Storage Temperature
Symbol
VCC
IIN
VIN
IOUTDRV
Ta
Tstg
Min
-0.3
-0.3
max
6.0
±10
6.0(VCC+0.3)
50
70
150
-20
-65
Units
V
mA
V
mA
°C
°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
Power Supplies
Symbol
VCC
Min
2.7
typ
3.3
max
3.6
Units
V
Note 1. All voltages with respect to ground.
WARNING: AKM assumes no responsibility for the usage beyond the conditions in this datasheet.
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Analog Characteristics
Ta=-20°C to 70°C, VCC=2.7V, External Vref =2.5V, fs=125kHz, fDCLK=16*fs, 12bit mode
Parameter
min
ADC for Touch Screen
Resolution
No Missing Codes
11
Integral Linearity Error
DNL
Analog Input Voltage Range
0
Offset Error
Gain Error
Touch Panel Driver
XP, YP, RL=300Ω
XN, YN, RL=300Ω
XP Pull Up Register (when pen interrupt enable)
PSRR (10KHz 100mVpp)
Reference Output
Internal Reference
2.44
Drift
Load Capacitance
0.1
Reference Input
Input Voltage Range
Battery Monitor
Input Voltage Range
Input Impedance (Battery Measure Mode)
5
Accuracy (Note 2) External VREF = 2.5V is used
Accuracy (Note 2) Internal Reference is used.
Temperature Measurement
Temperature Range
-20
Resolution (Note 3)
Accuracy (Note 4)
Power Supply Current
Normal Mode (Internal Reference OFF)
Normal Mode (Internal Reference ON)
Full Power Down(when writing control command with PD1=PD0= “0”)
typ
max
12
12
±2
±1
Vref
±6
±4
2.56
V
ppm/°C
μF
VCC
V
5.0
V
KΩ
%
%
10
±2
±3
70
°C
°C
°C
500
800
3
μA
μA
μA
1.6
±3
250
520
0
Bits
Bits
LSB
LSB
V
LSB
LSB
Ω
Ω
KΩ
dB
5
5
50
70
2.50
30
Units
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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DC Characteristics (Logic I/O)
Ta=-20 to 70°C, VCC=2.7V to 3.6V
Parameter
“H” level input voltage
“L” level input voltage
Input Leakage Current
“H” level output voltage (@ Iout = -250uA)
“L” level output voltage
(@ Iout= 250uA)
Tri-state Leakage Current
All pins except for XP, YP, XN, YN pins
XP, YP, XN, YN pins
PENIRQN “L” level output voltage (100KΩ Pull-Up)
Symbol
VIH
VIL
IILK
VOH
VOL
IOLK
min
0.8xVCC
typ
-
-10
VCC-0.4
-
-
-10
-50
VOLP
max
0.4
Units
V
V
μA
V
V
10
50
0.8
μA
μA
V
max
Units
125
kHz
2100
60
kHz
%
μs
1/fDCLK
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
0.2xVCC
10
Switching Characteristics
Ta=-20°C to 70°C, VCC=2.7V to 3.6V
Parameter
Touch Panel (A/D Converter)
Throughput Rate
DCLK
frequency
duty
Tracking Time (Rin=600Ω) (Note 5)
Conversion Time
CSN “↓” to First DCLK “↑”
CSN “↓” to BUSY Tri-State Disabled
CSN “↓” to DOUT Tri-State Disabled
DCLK High Pulse Width
DCLK Low Pulse Width
DCLK “↓” to BUSY “↑”
Data Setup Time
Data Valid to DCLK Hold Time
Data Access Time after DCLK “↓”
CSN “↑” to DCLK Ignored
CSN “↑” to BUSY High-Z state
CSN “↑” to DOUT High-Z state
Symbol
min
typ
Fs
fDCLK
duty
tTRK
tCONV
t1
t2
t3
t4
t5
t6
t7
t8
t9
t10
t11
t12
10
40
1.428
50
12
100
200
200
190
190
160
100
10
160
0
200
200
Note 5. The actual tracking periods are 3tDCLK. (tDCLK=1/fDCLK)
CSN
50%VCC
t5
t1
t6
t6
t9
t4
t10
DCLK
50%VCC
t8
t7
PD0
50%VCC
DIN
t2
t11
VOH
BUSY
VOL
t12
t3
DOUT
D11
D10
D0
Figure 1 AK4181A Timing Diagram
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VOH
VOL
[AK4181A]
A/D Converter for Touch Screen
The AK4181A incorporates a 12-bit successive approximation resistor (SAR) A/D converter for position measurement,
temperature, and battery voltage. The architecture is based on capacitive redistribution algorithm, and an internal capacitor array
functions as the sample/hold (S/H) circuit.
The SAR A/D converter output is a straight binary format as shown below:
Input Voltage
Output Code
FFFH
(ΔVREF-1.5LSB)~ ΔVREF
FFEH
(ΔVREF-2.5LSB) ~ (ΔVREF-1.5LSB)
----------------0.5LSB ~ 1.5LSB
001H
0 ~ 0.5LSB
000H
ΔVREF: (VREF+) – (VREF-)
Table 1 Output Code
The full scale (ΔVREF) of the A/D converter depends on the input mode. The AK4181A is controlled by the 8 bit serial command
on DIN.
Analog Inputs
Analog input is selected via the A2, A1, A0 and SER/ DFR bits in the control register. If the analog inputs are selected to the X
or Y-axis, SER/ DFR = “0”, which means differential mode, the full scale (ΔVREF) is the differential voltage between the noninverting terminal and the inverting terminal of the measured axis (e.g. X-axis measurement:(XP) – (XN)). Analog non-inverting
input to A/D converter is the non-inverting terminal of the non-measured axis while the inverting input is the inverting terminal of
the measured axis. If the SER/ DFR bit is set to “1” which means single-ended mode, the full scale of A/D converter (ΔVREF)
is the internal reference voltage or external reference voltage. Note that SER/ DFR bit should be set to ”0” if IN2 is selected as
analog input; nevertheless, IN2 is actually measured by single-ended mode.
Tracking time is the period from the falling edge of 5th DCLK to that of 8th DCLK after the detection of START bit during
CSN=”L”.
The required settling time to charge the internal capacitor array depends on the source impedance (Rin). If the source impedance is
600 ohm, the settling time needs at least 1.428μs (3tDCLKat 2.1MHz). The maximum throughput of A/D converter is 125 kHz.
If the source impedance of analog input or battery input is larger than 600 ohm, longer tracking time is required.
The Position Detection of 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-dimensional (X/Y axis) position.
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[AK4181A]
ON
ON
XP
VREF
XP
AIN+
VREF
YP
ADC
VREF-
AIN+
YP
ADC
VREF-
AIN-
AIN-
XN
XN
ON
YN
YN
ON
a)
X-Position Measurement Differential Mode
b)
Y-Position Measurement Differential Mode
Figure 2 Axis Measurement
The differential mode position detection is typically more accurate than the single-ended mode. As the full scale of single-ended
mode is fixed to the internal (or external) reference voltage, input voltage may exceed the full-scale reference voltage. This
problem does not occur in differential mode. In addition to this, the differential mode is less influenced by power supply voltage
variation due to the ratio-metric measurement.
However, note that the touch screen driver switch is still ON and the current flows even for the A/D conversion time. On the other
hand, the touch screen driver switch is ON only for the tracking time, 3tDCLK. From the point of power consumption, singleended mode has more advantages.
The Pen Pressure Measurement
The touch screen pen pressure can be derived from the measurement of the contact resistor between two plates. The contact
resistance depends on the size of the depressed area and the pressure. The area of the spot is proportional to the contact resistance.
This resistance (Rtouch) can be calculated using two different methods.
The first method is that when the total resistance of the X-plate sheet is already known. The resistance, Rtouch, is calculated from
the results of three conversions, X-position, Z1-Position, and Z2-Position, and then using the following formula:
Rtouch = (Rxplate) * (Xposition/4096) * [ (Z2/Z1) – 1]
The second method is that when both the resistances of the X-plate and Y-plate are known. The resistance, Rtouch, is calculated
from the results of three conversions, X-position, Y-Position, and Z1-Position, and then using the following formula:
Rtouch = (Rxplate*Xposition/4096)*[(4096/Z1) – 1] – Ryplate*[1 – (Yposition/4096)]
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[AK4181A]
ON
ON
YP
YP
XP
VREF+
AIN+
VREF-
AIN-
touch
XP
ADC
VREF+
AIN+
VREF-
AIN-
touch
ADC
XN
XN
ON
ON
YN
a)
YN
b)
Z1-Position Measurement Differential Mode
Z2-Position Measurement Differential Mode
Figure 3 Pen Pressure Measurements
Voltage Reference
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”.
Battery Measurement
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.
VREF
PD1
Internal
VREF(2.5V)
VBAT
AIN+
R0
VREF+
ADC
R1=7.5K
AIN-
VREF-
R2=2.5K
Enable
Figure 4 Battery Monitoring
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[AK4181A]
Temperature Measurement
Equation <1> describes the forward characteristics of the diode.
<1>
iD=I0exp(vD/VT) ( VT = kT/q)
I0: reverse saturation current
q : 1.602189×10-19 (electron charge)
k : 1.38054×10-23 (Boltzmann’s constant)
vD: voltage across diode
T: absolute temperature K
The diode characteristic is approximately shown as a diode junction voltage. That is theoretically proportional to the temperature;
the ambient temperature can be predicted by knowing this voltage.
Temp.
Sensor
I
TEMP0
82I
TEMP1
Figure 5 Temperature Measurement
As the AK4181A has two different fixed current circuits and a diode (temperature sensor), the temperature can be measured by
using two different methods.
The first method needs two conversions, but can derive the temperature directly without knowing the voltage at a specific
temperature.
From equation <1>
(iD2 / iD1) = exp{(v(NI) - v(I))/VT}
N = (iD2 / iD1) = 82 (ratio of the current)
T°C = (ΔVbe * q)/(k * ln N) – 273
ΔVbe = V(82I) – V(I)
T°C = 2.63×103 × ΔVbe – 273
The second method needs only one conversion as the following equation, but requires knowing the junction voltage at the specific
temperature.
T = (k/q)* vD/ln(iD/I0)
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<2>
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Control Command
The control command, 8 bits, provided to the AK4181A via DIN is shown in the following table. This command includes start bit,
channel selection, resolution, measurement configuration, and power-down mode. The AK4181A latches the serial command at
the rising edge of DCLK. Table 2 gives detailed information regarding the bit order, function, the status of driver switch, ADC
input, reference voltage.
D7
S
D6
A2
BIT
7
6-4
Name
S
A2-A0
3
2
MODE
SER/ DFR
3
PD1-PD0
D5
A1
A1
A0
D3
MODE
D2
D1
PD1
SER/ DFR
D0
PD0
Function
Start Bit. This bit must be “H” because the AK4181A initiates the command recognition
Channel Selection Bits. Analog inputs to the A/D converter and the activated driver switches are
selected. Please see the following table for the detail.
Resolution of A/D converter. ”L”: 12 bit output “H”: 8 bit output
Measurement Mode (Single-Ended/Differential)
Power-down Mode (reference to “ Power-down Control”)
Control Command
A2
D4
A0
Status of Driver Switch
SER/
XP
XN
YP
YN
AIN+
AIN-
Reference Voltage
(ΔVREF)
VREF+
VREF-
OFF
OFF
OFF
OFF
OFF
ON
OFF
OFF
OFF
OFF
OFF
ON
ON
ON
OFF
OFF
OFF
ON
OFF
ON
ON
OFF
OFF
OFF
OFF
ON
OFF
OFF
OFF
OFF
OFF
OFF
TEMP0
XP
VBAT
XP(Z1)
YN(Z2)
YP
IN1
TEMP1
GND
GND
GND
GND
GND
GND
GND
GND
VREF
VREF
VREF
VREF
VREF
VREF
VREF
VREF
GND
GND
GND
GND
GND
GND
GND
GND
OFF
OFF
ON
ON
XP
YN
YP
YN
OFF
OFF
ON
OFF
ON
ON
ON
OFF
ON
ON
OFF
OFF
OFF
OFF
OFF
OFF
XP(Z1)
YN(Z2)
YP
IN2
XN
XN
XN
GND
YP
YP
XP
VREF
XN
XN
XN
GND
ADC input (ΔAIN)
Note
DFR
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
TEMP0
Y-axis
Battery Monitor
Z1 (Pen Pressure)
Z2 (Pen Pressure)
X-axis
IN1
TEMP1
NA
Y-axis
NA
Z1 (Pen Pressure)
Z2 (Pen Pressure)
X-axis
IN2 (Note 6)
NA
Note 6. Note that IN2 auxiliary input is measured by single-ended mode although SER/ DFR bit is “0”.
Table 2 Control Command List
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[AK4181A]
Power-down Control
Power-down is controlled by two bits, PD0 bit and PD1 bit. The power-down state of internal voltage reference is controlled by
PD1 bit, and is updated at the rising edge of 7th DCLK with CSN = “L”.
The power-down state of A/D converter, and touch screen driver switches is controlled by PD0 bit, and is updated at the rising
edge of 8th DCLK with CSN = “L”.
If PD0 bit is set to “1”, the state of the driver switches is maintained until the 5th DCLK↑ of the next conversion if CSN is “L”. If
CSN is “H”, all driver switches except for YN switch switches are turned off and are open states. Only YN driver switch is turned
ON and YN pin is forced to the ground in this case.
PD1
0
PD0
0
PENIRQN
Enabled
0
1
Enabled
1
0
Enabled
1
1
Disabled
Function
Auto Power-down Mode.
A/D converter is automatically powered up at the start of the conversion, and goes to power- down
state automatically at the end of the conversion. And the AK4181A is always powered down at this
mode if CSN= “H”. All touch screen driver switches except for YN switch are turned off and
relative pins are open state. Only YN driver switch is turned ON and YN pin is forced to the ground
in this case. PEN interrupt function is enabled except for the tracking time and conversion time even
CSN= “L”. Please see “ PEN Interrupt” for the detail. The internal voltage reference is always
power-down state.
ADC ON Mode
A/D converter is always powered up while CSN = “L”. The internal voltage reference is always
power-down state. If X-axis or Y-axis is selected as analog input, touch screen driver switches are
always turned ON and the current flows through the touch plate if CSN= “L”. This is effective if
more settling time is required to suppress the electrical bouncing of touch plate.
VREF ON Mode
The internal voltage reference is always powered up regardless of CSN state. ADC is auto powerdown mode. PEN interrupt function is enabled at all the period except for the period from the
5DCLK↓ to 20DCLK↓ regardless of CSN state.
ADC and VREF ON Mode
A/D converter and the internal voltage reference is power-up state
PEN interrupt function is disabled and PENIRQN is forced to “H” state if CSN= “H”. The behavior
of PENIRQN is the same as “ADC ON Mode”
Table 3 Power-down Control
Serial Interface
The AK4181A is controlled via 4-wire serial interface, CSN, DCLK, DIN, DOUT.
Please see “ Switching Characteristics” for the detail.
CSN
1
2
3
4
5
6
7
8
MO SER/
DFR
PD1
PD0
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
DCLK
S
DIN
A2
A1
A0
S
A2
5
4
A1
A0
MO SER/
DFR
PD1
PD0
Hi-Z
BUSY
Hi-Z
11
10
9
8
7
6
3
2
1
0
11
10
DOUT
Driver SW
SER/ DFR
=”1”
Driver SW
SER/ DFR
=”0”
Figure 6 Serial Interface
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BUSY and DOUT goes to “L” from Hi-Z state at the falling edge of CSN. The AK4181A latches the 8bit control word serially via
DIN at the rising edge of DCLK. As the AK4181A starts the command decoding at the first “H” bit after CSN= “↓”, MSB (S bit)
of the command must be “H”.
Tracking time is the period from the falling edge of 5th DCLK to the falling edge of 8th DCLK. If SER/ DFR = “1”, PD0= “0”,
and if analog input is X-axis or Y-axis (the measurement is the pen position or pen pressure), the touch screen driver switches are
turned ON for this 3DCLK period. If SER/ DFR = “0”, the switches are turned ON for the period from 5DCLK↓ to 20 DCLK↓.
BUSY is “H” for one DCLK period, which is from 8DCLK↓ to 9DCLK↓. BUSY is “L” for other period.
The AK4181A outputs A/D data with MSB first via DOUT from the falling edge of 9th DCLK.
DIN must keep low state for minimum 7 DCLK times (9th-15th DCLK) after command is sent on the DIN.
The AK4181A can output one A/D data per 15 DCLK clock cycles for the fastest way as shown in the dotted line of the Figure 6.
Pen Interrupt
The AK4181A has pen interrupt function to detect the pen touch. Pen interrupt function is enabled at power-down state. YN pin is
connected to GND at the PEN interrupt enabled state. And XP pin is pulled up via an internal resistor (Ri), typically 50k ohm.
PENIRQN pulled up via an external resistor, 100k ohm, is also connected to XP pin. If touch plate is pressed by pen the current
flows via <VCC> – <Ri> – <XP> –<the plates> - <YN>. The resistance of the plate is generally 1k ohm or less, PENIRQN is
forced to “L” level. If the pen is released, PENIRQN returns “H” level because two plates are disconnected, and the current
doesn’t flow via two plates.
If the plate is touched with pen or finger, PENIRQN goes to “L” at CSN = “H” unless previous command issued with both PD1
and PD0 is “1”. PENIRQN is disabled and keeps “H” level regardless of the touched/non-touched state if CSN = “H”.
The operation of PENIRQN is related to PD0 bit. PD0 bit is updated at the rising edge of 8th DCLK (please see “ Power-down
Control” for the detail). Therefore, the last PD0 bit is valid until this timing. (The internal voltage reference is controlled by only
PD1 bit regardless of PD0 bit and CSN state.)
i.
The period from the 5th DCLK↓ to the 20th DCLK↓
The behavior of PENIRQN is related to the selected analog input. If the X-axis or Y-axis is selected as analog input, PENIRQN
is forced to “L” regardless of the touched/non-touched state. If the temperature, VBAT, or auxiliary inputs is selected,
PENIRQN is forced to “H” regardless of the touched/non-touched state.
ii.
The period from CSN↓ to the 5th DCLK.
The behavior of PENIRQN is related to the combination of the last selected analog input channel, and the last PD0 bit. If the
last PD0 bit was set to “0”, PENIRQN is “H” while the plate is not pressed, and “L” while the plate is pressed regardless of the
last analog input. If the last PD0 bit was set to “1”, the last analog input decides the level of PENIRQN. If the last analog input
channel is ether X-axis or Y-axis, PENIRQN is “L” for all the time in this period regardless of the touched/non-touched state.
On the other hand, if the last analog input is temperature, VBAT, or auxiliary inputs, PENIRQN is “H” for all the time in this
period regardless of the touched/non-touched state.
iii.
The period from the 20th DCLK↓ to CSN↑
The behavior of PENIRQN is related to the combination of the current selected analog input channel, and the current PD0 bit.
If the current PD0 bit is set to “0”, PENIRQN is “H” while the plate is not pressed, and “L” while the plate is pressed regardless
of the current selected analog input. If the current PD0 bit is set to “1”, the current analog input decides the operation of
PENIRQN. If the current analog input channel is ether X-axis or Y-axis, PENIRQN is “L” for all the time in this period
regardless of the touched/non-touched state. On the other hand, if the current analog input is temperature, VBAT, or auxiliary
inputs, PENIRQN is “H” for all the time in this period regardless of the touched/non-touched state.
It is recommended that the micro controller mask the pseudo-interrupts while the control command is issued or A/D data is output.
Full power down (CSN = “H”, DIN = “H”, DCLK= “L” or “H”) should force internal register to initial value 00H and XP, YP, XN
pin to Hi-z state. In addition to this, the current does not flow even if the plate is touched with pen or finger. PENIRQN goes to
“H” regardless of pen touch at full power.
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[AK4181A]
100kΩ
PENIRQN
EN2
50kΩ
Driver OFF
XP
EN1
YN
Driver ON
Figure 7 PENIRQ Functional Block Diagram
CSN
1
2
3
4
5
6
7
8
MO SER/
DFR
PD1
PD0
9
10
11
12
13
14
15
16
9
8
7
6
5
17
18
19
20
21
22
23
24
DCLK
DIN
S
A2
A1
A0
BUSY
11
10
4
3
2
1
0
DOUT
CONV
Internal
AXIS = ((!A2) & (!A1) & (A0))
| ((!A2) & (A1) & (A0))
| ((A2) & (!A1) & (!A0))
| ((A2) & (!A1) & (A0));
/* X-axis Measurement */
/* Z1 Measurement */
/* Z2 Measurement */
/* Y-axis Measurement */
EN1 = ((!CSN) & (!CONV) & AXIS & PD0)
/* CSN=”L”, X/Y/Z1/Z2 Measurement, PD0 = 1, NOT “CONV period” */
| ((!CSN) & AXIS & CONV);
/* CSN=”L”, X/Y/Z1/Z2 Measurement, “CONV period” */
EN2 = ((!CSN) & (!CONV) & (!PD0))
/* CSN=”L”, PD0 = 1, NOT “CONV period” */
| (CSN & (!(PD1& PD0));
/* CSN=”H”, (PD0, PD1) is not (1,1) */
Power on Sequence
On the AK4181A first powers up, the register value including power down mode, internal reference (PD1, PD0) holds unfixed
before sending first control command. On this condition pen interrupt function may be disable, internal reference may also be ON
state ([PD1, PD0] = [1,1]). 8bit control command must be sent as quick as possible when first power up to fix the internal register
value. The sequence is that 1) Power On with CSN = “L” or “H” then CSN = “H”. 2) Send control command after CSN = “L”. 3)
CSN = “H” again. Once sending command to fix the internal register after first power up, the state of AK4181A is held on the
condition of state as last command issued.
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[AK4181A]
Package
16pin TSSOP (Unit: mm)
1.1 (max)
*5.0±0.1
16
9
8
1
0.13
M
6.4±0.2
*4.4±0.1
A
0.65
0.22±0.1
0.17±0.05
Detail A
0.5±0.2
0.1±0.1
Seating Plane
0.10
NOTE: Dimension "*" does not include mold flash.
0-10°
Package & Lead frame material
Package molding compound: Epoxy
Lead frame material: Cu
Lead frame surface treatment: Solder (Pb free) plate
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[AK4181A]
Marking
AKM
4181AVT
XXYYY
Contents of XXYYY
XX:
Lot #
YYY:
Date Code
REVISION HISTORY
Date (YY/MM/DD)
04/08/30
10/09/17
MS0313-E-02
Revision
01
02
Reason
First Edition
Specification
Change
Page
Contents
15
Package
The package dimensions were changed.
16
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[AK4181A]
IMPORTANT NOTICE
z These products and their specifications are subject to change without notice.
When you consider any use or application of these products, please make inquiries the sales office of Asahi Kasei
Microdevices Corporation (AKM) or authorized distributors as to current status of the products.
z Descriptions of external circuits, application circuits, software and other related information contained in this
document are provided only to illustrate the operation and application examples of the semiconductor products.
You are fully responsible for the incorporation of these external circuits, application circuits, software and other
related information in the design of your equipments. AKM assumes no responsibility for any losses incurred by
you or third parties arising from the use of these information herein. AKM assumes no liability for infringement
of any patent, intellectual property, or other rights in the application or use of such information contained herein.
z Any export of these products, or devices or systems containing them, may require an export license or other
official approval under the law and regulations of the country of export pertaining to customs and tariffs,
currency exchange, or strategic materials.
z AKM products are neither intended nor authorized for use as critical componentsNote1) in any safety, life support,
or other hazard related device or systemNote2), and AKM assumes no responsibility for such use, except for the
use approved with the express written consent by Representative Director of AKM. As used here:
Note1) A critical component is one whose failure to function or perform may reasonably be expected to
result, whether directly or indirectly, in the loss of the safety or effectiveness of the device or system
containing it, and which must therefore meet very high standards of performance and reliability.
Note2) A hazard related device or system is one designed or intended for life support or maintenance of
safety or for applications in medicine, aerospace, nuclear energy, or other fields, in which its failure to
function or perform may reasonably be expected to result in loss of life or in significant injury or damage to
person or property.
z It is the responsibility of the buyer or distributor of AKM products, who distributes, disposes of, or otherwise
places the product with a third party, to notify such third party in advance of the above content and conditions,
and the buyer or distributor agrees to assume any and all responsibility and liability for and hold AKM harmless
from any and all claims arising from the use of said product in the absence of such notification.
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