ASAHI KASEI
[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 7
th
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 8
th
DCLK with CSN = “L”.
If PD0 bit is set to “1”, the state of the driver switches is maintained until the 5
th
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
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 power-
down 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
0
1
Enabled
1
0
Enabled
1
1
Disabled
Serial Interface
The AK4181A is controlled via 4-wire serial interface, CSN, DCLK, DIN, DOUT.
Please see “
Switching Characteristics”
for the detail.
CSN
1
DCLK
S
A2
A1
A0
MO
SER/
DFR
PD1
PD0
S
A2
A1
A0
MO SER/
DFR
PD1
PD0
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
DIN
Hi-Z
BUSY
Hi-Z
DOUT
Driver SW
SER/ DFR
=”1”
11
10
9
8
7
6
5
4
3
2
1
0
11
10
Driver SW
SER/ DFR
=”0”
Figure 6 Serial Interface
MS0313-E-00
12
2004/06
AKM [ ASAHI KASEI MICROSYSTEMS ]
