APT7843
Touch Screen Controller
Description
The APT7843 Touch Screen Controller IC provides all
the screen drive , A/D converter and control circuits
to easily interface to 4 wire resistive touch screen.
The IC continually monitors the screen waiting for a
touch. When the screen touched , the IC performs
A/D converter to determine the location of touch.
Also , this device has 2 auxiliary input to A/D con-
verter , allowing for the measurement of other inputs
such as battery voltage.
Features
•
•
•
•
•
•
•
16 pin SSOP or TSSOP
Operates with four wire touch screen
8-bit or 12 bit A/D converter
Ratiometric Conversion eliminates screen
calibration
2 auxiliary analog inputs
4 wire serial interface
Full power down control
Applications
•
•
•
PDAs
Handheld computer
Touch-screen kiosks
Pin Assignment
+Vcc
X+
Y+
X-
Y-
GND
IN3
IN4
1
2
3
4
5
6
7
8
16
15
14
13
12
DCLK
CS
DIN
BUSY
DOUT
11 PENIRQ
10
9
+Vcc
V
REF
Order Information
APT7843
Temp. Range
Package Code
Package Code
N : SSOP
Temp. Range
I : - 40 to 85
°
C
O : TSSOP
ANPEC reserves the right to make changes to improve reliability or manufacturability without notice, and advise
customers to obtain the latest version of relevant information to verify before placing orders.
Copyright
ANPEC Electronics Corp.
Rev. A.8 - Apr., 2002
1
www.anpec.com.tw
APT7843
Block Diagram
PENIRQ
X+
X-
Screen Driver
DCLK
CS
MUX
12 Bit or 8 Bit
A/D Converter
Serial
Interface
Y+
Y-
IN3
IN4
V
REF
DIN
DOUT
BUSY
Pin Descriptions
PIN
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
NAME
+Vcc
X+
Y+
X-
Y-
GND
IN3
IN4
V
REF
DESCRIPTION
Power Supply,2.2V to 5V.
Connect to X+ on touch screen.
Connect to Y+ on touch screen.
Connect to X- on touch screen.
Connect to Y- on touch screen.
Ground
Auxiliary Input of A/D converter.
Auxiliary input of A/D converter.
Voltage Reference Input.
+Vcc
Power Supply,2.2V to 5V.
PENIRQ Pen interrupt. Open anode output (requires
10kΩ to 100kΩ pull-up resistor externally)
DOUT Serial Data Output. This output is high
impedance when CS is HIGH.
BUSY Busy Output. This output is high impedance
when
CS
is HIGH.
DIN
Serial Data input.
CS
DCLK
Chip Select. (Active Low)
Serial Clock.
Copyright
ANPEC Electronics Corp.
Rev. A.8 - Apr., 2002
2
www.anpec.com.tw
APT7843
Electrical Characteristics
At T
A
= -40°C to 85°C , V
CC
= +2.7V , V
REF
= +2.5V , f
SAMPLE
= 125kHz , f
CLK
= 16 • f
SAMPLE
= 2MHz , 12-bit mode
, and digital inputs = GND or V
cc
, unless otherwise noted.
PA R A M E T E R
DC ACCURACY
R esolu tio n
N o m issing co de
Integra l N onlin earity
O ffset E rror
O ffset E rror M atch
G ain E rror
G ain E rror M atch
N oise
P ow er S u pply R ejectio n
R E F E R A N C E IN P U T
V
R E F
In put Voltage R an ge
D C Le akage C urrent
V
R E F
In put Im p eda nce
V
R E F
In put C urrent
F
S A M P LE
= 12 .5 kH z
C S = V cc
D Y N A M IC P E R F O R E N C E
A perture D e lay
A perture Jitter
C han nel to C han ne l Isolation
C O N V E R S IO N R AT E
C onversion Tim e
Track/H old A cquis ition Tim e
T hrough put R ate
S W IT C H D R IV E R S
O n-R esistance
Y+ , X+
Y- , X-
L O G IC O U T P U T S
O utput H ig h Vo lta ge , V
O H
O utput Low Voltage , V
O L
PEN IR Q output low voltage , V
O L
Floating-S tate Leakage C urrent
Floating-State Output Capacitance
O utput C oding
|I
O H
|
≤
-250
µ
A
|I
O L
|
≤
250
µ
A
V cc–0.2
0.4
0.2
±
10
10
S traight ( N atura l ) B in ary
V
V
V
µ
A
pF
4
4
15
15
Ω
Ω
3
125
12
DCLK cycles
DCLK cycles
KSPS
V
IN
= 2.5 V p-p ; F
IN
= 5 0kH z
30
100
100
ns
ps
dB
C S = G N D or V cc
1.0
±
1
5
13
2.5
3
40
V cc
µ
A
G
Ω
µ
A
µ
A
µ
A
0.1
30
70
0.1
11
±
2
±
6
1
±
4
1
12
B its
B its
LS B
LS B
LS B
LS B
LS B
uV rm s
dB
C O N D IT IO N S
A P T 78 43
M IN
TYP
MAX
U N IT S
Note : (1) LSB means least Significant Bit. With V
REF
equal to +2.5V , one LSB is 610µV
Copyright
ANPEC Electronics Corp.
Rev. A.8 - Apr., 2002
3
www.anpec.com.tw
APT7843
Electrical Characteristics (Cont.)
PA R A M E T E R
L O G IC IN P U T S
In p u t H ig h Vo lta g e ,
V
INH
In p u t L o w Vo lta g e ,
V
INL
Inp ut C urre nt , I
IN
In p u t C a p a c ita n c e ,
C
IN
A N ALO G IN P U T
In p u t Vo lta g e R a n g e s
D C Le aka ge C u rre nt
In p u t C a p a c ita n c e
P O W E R R EQ U IR E M EN T S
Vcc
Ic c
N orm a l M o d e (S ta tic )
N orm al M od e (F
S A M P L E
=
1 2 .5k S P S )
S hutdow n
M o d e (S ta tic)
Showdown
D ig ita l I/P s = 0 V o r V cc
V cc = 3.6V
V cc = 3.6V
650
540
3
V cc = 3.6V
3.6
µA
µA
µA
µW
2.7
3.6
V
C O N D IT IO N S
APT7843
M IN
2.4
0.8
±
1
10
0
±
0.1
30
V
REF
TYP
MAX
U N IT S
| I
I N H
|
≤
+ 5
µA
| I
I N L
|
≤
+ 5
µA
V
V
µA
pF
Vo lts
µA
pF
Copyright
ANPEC Electronics Corp.
Rev. A.8 - Apr., 2002
4
www.anpec.com.tw
APT7843
Electrical Characteristics
At T
A
= -40°C to 85°C, V
CC
= +2.4V , V
REF
don’t care, f
SAMPLE
= 1.25KHz, f
CLK
= 16 • f
SAMPLE
= 20KHz, 8-bit
differential mode, no support single end mode, and digital inputs = GND or V
cc
, unless otherwise noted.
PARAMETER
DC ACCURACY
Resolution
No missing code
Integral Nonlinearity
Offset Error
Offset Error Match
Gain Error
Gain Error Match
Noise
Power Supply Rejection
DYNAMIC PERFORENCE
Aperture Delay
Aperture Jitter
Channel to Channel Isolation
CONVERSION RATE
Conversion Time
Track/Hold Acquisition Time
Throughput Rate
SWITCH DRIVERS
On-Resistance
Y+ , X+
Y- , X-
LOGIC OUTPUTS
Output High Voltage , V
OH
Output Low Voltage , V
OL
PENIRQ output low voltage , V
OL
Floating-State Leakage Current
Floating-State Output Capacitance
Output Coding
CONDITIONS
APT7843
MIN
TYP
8
7
±
2
±
6
0.1
0.1
30
70
30
100
1
±
4
1
MAX
UNITS
Bits
Bits
LSB
LSB
LSB
LSB
LSB
uV rms
dB
ns
ps
dB
12
DCLK cycles
DCLK cycles
1.25
KSPS
V
IN
= 2.5Vp-p ; F
IN
= 50kHz
100
3
4
4
|I
OH
|
≤
-250µA
|I
OL
|
≤
250µA
Vcc–0.2
0.4
0.2
±
10
10
Straight ( Natural ) Binary
Ω
Ω
V
V
V
µA
pF
Copyright
ANPEC Electronics Corp.
Rev. A.8 - Apr., 2002
5
www.anpec.com.tw
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