Revision 2.0
Page 1 of 12
austria
micro
systems
Key Features
-
16-digit LCD driver on a 44 pin CMOS chip
-
Operating voltage range: 3.2 to 4.8V
-
Low power consumption: max. 150 A
-
Driving 7-segment displays with up to 16 digits and 12
symbols
-
Option for 12 digits
-
Buffer for 32 digits
-
4 backplanes
-
2-wire interface
-
On chip timer for showing elapsed time
-
Contrast adjustable
-
On chip oscillator using 32.768 kHz crystal
-
Compatible with AS2525
Package
Available in 44 pin TQFP.
Block Diagram
General Description
The AS2591 is a CMOS integrated circuit for driving a
liquid crystal display intended for use in telephones. The
driver can be used with 12- or 16-digit LCDs.
The 2-wire serial interface is compatible with the AS2525,
single-chip handsfree telephone circuit.
The device is designed for LCDs with 4 backplanes and 24
or 31 segments providing 12 or 16 7-segment digits and 12
symbols.
The AS2591 also includes a timer for showing elapsed time
in minutes and seconds.
The contrast can be adjusted through the serial interface.
SERIAL
I/F
7-
SEGMENT
DECODER
DIGIT
MEMORY
32 DIGITS
COMMAND
DECODER
BACKPLANE
COUNTER
ELAPSE
TIME
COUNTER
TIMER
POR
OSC
CONTRAST
VOLTAGE
CONTROL
4
16
16
LCD
SEGMENT
MULTIPLEXER
V
DD
DI
SCLK
CS
V
LCD
32.768 kHz
AS2591
DATA
ADDRESS
CONTROL
COM1-4
S1_n
S2_n
Figure 1: Block diagram
16-Digit LCD Driver
CMOS Integrated Circuit
AS2591
DATA SHEET
Data Sheet AS2591
austria
micro
systems
Revision 2.0
Page 2 of 12
Pin Description
Pin #
Name
Type
Description
1
2
3
4
5
6
7
8
9
10
11
12
S2_10
S1_10
S2_11
S1_11
S2_12
S1_12
S2_13
S1_13
S2_14
S1_14
S2_15
S1_15
AO
S
egment Outputs
Output pins for driving segments of LCD.
13
CS
DI
C
hip
S
elect
Chip select signal from CPU (e.g. AS2525).
14
DI
DI
D
ata
I
nput
Data input pin for serial interface.
15
SCLK
DI
S
erial
Cl
oc
k
Input
Clock input pin for serial interface.
16
V
DD
Supply
V
oltage
D
rain
D
rain
This pin is the positive power supply for the device.
17
V
SS
Supply
V
oltage
S
ource
S
ource
This pin is the negative power supply for the device.
18
19
XTAL1
XTAL2
Oscillator Pins
Oscillator pins for connection of a 32.768 kHz crystal.
20
V
LCD
AI
LCD
Reference
V
oltage
This is the input pin for setting the internal LCD reference voltage (see also
Figure 3: Supply arrangement).
21
22
23
24
COM1
COM2
COM3
COM4
AO
Backplane Outputs
Output pins for driving backplanes of LCD.
Data Sheet AS2591
austria
micro
systems
Revision 2.0
Page 3 of 12
Pin #
Name
Type
Description
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
S2_0
S1_0
S2_1
S1_1
S2_2
S1_2
S2_3
S1_3
S2_4
S1_4
S2_5
S1_5
S2_6
S1_6
S2_7
S1_7
S2_8
S1_8
S2_9
S1_9
AO
S
egment Outputs
Output pins for driving segments of LCD.
DI:
Digital Input
AI:
Analogue Input
DO:
Digital Output
AO:
Analogue Output
DI/O:
Digital Input/Output
AI/O:
Analogue Input/Output
Data Sheet AS2591
austria
micro
systems
Revision 2.0
Page 4 of 12
Typical Application
Figure 2: Typical Application
See also application note AN525 for further information.
Data Sheet AS2591
austria
micro
systems
Revision 2.0
Page 5 of 12
Functional Description
AS2591 is a CMOS mixed-mode integrated circuit for
driving LCDs with 4 backplanes and 24 or 31 segments
providing 12 or 16 7-segment digits and 12 symbols. The
device is controlled via a simple 2-wire bus and a chip-
select signal. The device also includes an elapse-time
counter which is started 5 seconds after power-up and
incremented every second.
The timer is re-started whenever the device gets a WRITE-
DIGIT or SHIFT&WRITE command within the first 5 counts
(except commands for displaying digits "-", "
o
", "o"). The
content of the timer is displayed 5 second after receiving
the last WRITE-DIGIT, SHIFT&WRITE or BLINKING
command. The normal display appears immediately after
receiving a WRITE-DIGIT, SHIFT&WRITE, or BLINKING
command.
Supply Arrangement
The device is supplied through V
DD
. The internal reference
voltages (V
33
, V
23
, and V
13
) for the backplane and segment
outputs are set at pin V
LCD
. With V
LCD
set to 3.27V the
segment output voltage is 2.97V (middle).
This voltage can be programmed through the serial bus to
2.83V (low) or 3.09V (high) for optimizing the contrast of
the LCD. The 1/3, 2/3, and 3/3 voltages are generated
internally (see Figure 3: Supply arrangement). In
applications with varying V
DD
, it is recommended to insert a
voltage regulator at V
LCD
in order to assure a constant
contrast (see also application note AN525 for further
information).
V
DD
V
SS
From
AS2525
V
LCD
V
DD
V
33
Contrast
control
V
23
V
13
Contrast
control
Figure 3: Supply arrangement
LCD Digit Code
Code [HEX]:
01
02
03
04
05
06
07
08
09
00
Number:
1
2
3
4
5
6
7
8
9
0
Display:
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Code [HEX]:
0A
0B
0C
0D
0E
0F
10
11
12
13
14
Letters/Signs:
a
b
c
d
e
f
#
*
-
(
)
Display:
_
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Code [HEX]:
15
16
17
18
19
1A
1B
1C
1D
1E
1F
Letters/Signs:
H
I
L
N
O
P
R
T
U
Display:
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