Preliminary
AS2591
Rev. 1.0
Page 1
May 1999
Key Features
q
q
16-digit LCD driver on a 44 pin CMOS chip
q
q
Operating voltage range: 3.2 to 4.8V
q
q
Low power consumption: max. 150 A
q
q
Driving 7-segment displays with up to 16 digits and
12 symbols
q
q
Option for 12 digits
q
q
Buffer for 32 digits
q
q
4 backplanes
q
q
2-wire interface
q
q
On chip timer for showing elapsed time
q
q
Contrast adjustable
q
q
On chip oscillator using 32.768 kHz crystal
q
q
Compatible with AS2525
Block Diagramme
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.
Package
Available in 44 pin TQFP.
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
S
E
G
M
E
N
T
M
U
L
T
I
P
L
E
X
E
R
V
DD
DI
SCLK
CS
V
LCD
32.768 kHz
AS2591
DATA
ADDRESS
CONTROL
COM1-4
S1_n
S2_n
Figure 1: Block diagram
Austria Mikro Systeme International AG
16-Digit LCD Driver
CMOS Integrated Circuit
Preliminary
AS2591
Rev. 1.0
Page 2
May 1999
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
Segment Outputs
Output pins for driving segments of LCD.
13
CS
DI
Chip Select
Chip select signal from CPU (e.g. AS2525).
14
DI
DI
Data Input
Data input pin for serial interface.
15
SCLK
DI
Serial Clock Input
Clock input pin for serial interface.
16
V
DD
Supply
Positive Voltage Supply
This pin is the positive power supply for the device.
17
V
SS
Supply
Negative Voltage Supply
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 Voltage
This is the input pin for setting the internal LCD reference voltage (see
also Figure 4: Supply arrangement).
21
22
23
24
COM1
COM2
COM3
COM4
AO
Backplane Outputs
Ouput pins for driving backplanes of LCD.
Continues...
Preliminary
AS2591
Rev. 1.0
Page 3
May 1999
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
Segment 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
Pin Configuration
AS2591
S
1
_
9
S
2
_
9
S
1
_
8
S
2
_
8
S
1
_
7
S
2
_
7
S
1
_
6
S
2
_
6
S
1
_
5
S
2
_
5
S
1
_
4
S2_4
S1_3
S2_3
S1_2
S2_2
S1_1
S2_1
S1_0
S2_0
COM4
COM3
S2_10
S1_10
S2_11
S1_11
S2_12
S1_12
S2_13
S1_13
S2_14
S1_14
S2_15
S
1
_
1
5
C
S
D
I
S
C
L
K
V
D
D
V
S
S
X
T
A
L
1
X
T
A
L
2
V
L
C
D
C
O
M
1
C
O
M
2
1
6
17
28
39
Figure 2: Pin configuration
Preliminary
AS2591
Rev. 1.0
Page 4
May 1999
Typical Application
Figure 3: Typical Application
See also application note AN525 for further information.
Preliminary
AS2591
Rev. 1.0
Page 5
May 1999
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 optimising the
contrast of the LCD. The 1/3, 2/3, and 3/3 voltages
are generated internally (see Figure 4: 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 4: 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:
|
|
_
_|
|_
_
_|
_|
|_|
|
_
|_
_|
_
|_
|_|
_
|
|
_
|_|
|_|
_
|_|
_|
_
| |
|_|
Code [HEX]:
0A
0B
0C
0D
0E
0F
10
11
12
13
14
Letters/Signs:
a
b
c
d
e
f
#
*
-
(
)
Display:
_
|_|
| |
|_
|_|
_
|_
_|
|_|
_
|_
|_
_
|_
|
_
_
_
|_
|
_
_
|
|_
_
|
_|
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:
|_|
| | |
|
|_
_
| |
_
|_|
_
|_|
|
_
|
|_
|_
|_|
_
|_|
Preliminary
AS2591
Rev. 1.0
Page 6
May 1999
LCD Symbols
Each symbol is associated with a fixed digit address. The circuit has 12 symbols implemented associated with the
lower 12 addresses.
Table 1: Symbol Overview
Enabled
Address
Name
Description
Always
y0
KL
Key lock activated
Optional
y1
SP
Loudspeaker on
Always
y2
MT
Mute activated
Optional
y3
MF
DTMF dialling mode selected
Optional
y4
LD
Loop disconnect (pulse) dialling mode selected
Optional
y5
Vol
Volume control keys activated. Remains on 2 seconds after last volume
key pressure
Always
y6
MR
Memory redial key has been pressed. Remains on until next key pressure
Always
y7
BO
Bell off. Indicates that ringer has been turn off.
Always
y8
SH
Shift; indicates that shift key has been pressed. Remains on untill next key
pressure
Optional
y9
-
Not used
Optional
y10
RD
Indicates that last number redial has been activated
Always
y11
PG
Indicates program mode
Symbol data are not effected by a BLINKING or by a WRITE&SHIFT command. Symbols will be displayed
independently from selecting the upper bank of the 32 digit buffer to be displayed.
The symbol displayed depends on the layout of the LCD display. If the layout of the 12/16 digit LCD displays can
be done similar, the symbol mapping does not need to be stored in the EEPROM.
Serial Interface
The serial interface uses the pins CS (chip select), SCLK (serial clock line), and DI (data input). A frame consists of
a 3-bit command and 5-bit data (see Figure 5: Frame of serial interface). Commands are executed self-timed by
the internal clock and commence at the falling edge of the CS signal.
CS
SCLK
DI
C3
C2
C1
D4
D3
D2
D1
D0
MSB
LSB
Figure 5: Frame of serial interface
Preliminary
AS2591
Rev. 1.0
Page 7
May 1999
Table 2: Commands
Command
[bin]
Data
[bin]/name
Description
000
address
Set pointer to address. If address is > 16/12, the upper bank of the 32-digit buffer
will be displayed. In case of a 12-digit display, up to address 23 will be displayed,
and if address is > 24 a third bank up to 32 will be displayed (see Table 4: 12-digit
display and Table 5: 16-digit display).
001
digit_code
Write digit code to active address.
010
digit_code
Shift & write digit code to address 0 (right most digit). Address pointer is set to 0..
011
1xBFS
Blinking ON at address:
BF blinking frequency S enabled/disabled
00
1.33 Hz
0
blinking
01
2.00 Hz
1
static off
10
0.67 Hz
11
1.00 Hz
0xxxx
Blinking OFF at address
100
1xxxx
Symbol ON at address
0xxxx
Symbol OFF at address
101
00xxx
Clear all digits, symbols, blinking, reset address to 0
10xxx
Clear all digits, blinking, reset address to 0
01xxx
Hide elapse time for 5 seconds.
11xxx
Hide elapse time permanently (note: Hide is reset by above command 101 01xxx).
110
xxFTM
Reserved for test modes
111
0xZxx
Display OFF and Cleared.
Z delay time
0
5 seconds
1
no delay
1CCND
Display ON (resets the off timer)
CC contrast voltage ND number of digits
00
low
00
12 digits
01
middle
01
16 digits
10
high
10
not allowed
11
not allowed
11
not allowed
Preliminary
AS2591
Rev. 1.0
Page 8
May 1999
Digit Layout
a
b
c
d
e
f
g
yn
Figure 6: Digit Layout
COM1 - 4 = common backplane signals
S1_n, S2_n = segment signals
n = 0 is most right digit, n= 11 is most left digit for 12-digit displays,
and n = 15 is most left digit for 16-digit displays.
Table 3: Backplanes and segments
COM1
COM2
COM3
COM4
S1_n
a
f
e
yn
S2_n
b
g
c
d
Segment Allocation
Table 4: 12-digit display
Symbol
Address
y11
y10
y9
y8
y7
y6
y5
y4
y3
y2
y1
y0
AS2525
PG
RD
-
SH
BO
MR
Vol
LD
MF
MT
SP
KL
Digits
Normal
11
10
9
8
7
6
5
4
3
2
1
0
Upper 1
23
22
21
20
19
18
17
16
15
14
13
12
Upper 2
31
30
29
28
27
26
25
24
Table 5: 16-digit display
Symbol Addr.
y11
y10
y9
y8
y7
y6
y5
y4
y3
y2
y1
y0
AS2525
PG
RD
-
SH
BO
MR
Vol
LD
MF
MT
SP
KL
Digits Normal
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Digits Upper
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
The symbols in bold are always enabled and other symbols can be enabled through the serial interface. Symbols
will be displayed independently from selecting the upper bank of the 32 digit buffer to be displayed.
The AS2591 incorporates a buffer for 32 digits. Digits are entered from the most right position and shifted left by
new entries (see also Table 2: Commands).
Preliminary
AS2591
Rev. 1.0
Page 9
May 1999
Electrical Characteristics
Absolute Maximum Ratings*
Supply Voltage............................................................................................................................... -0.3
V
DD
7V
Input Current..........................................................................................................................................+/- 25 mA
Input Voltage.....................................................................................................................-0.3V
V
IN
V
DD
+ 0.3V
Electrostatic Discharge...........................................................................................................................+/- 1000V
Storage Temperature Range........................................................................................................... -65 to +125C
Total Power Dissipation ............................................................................................................................ 500mW
*Exceeding these figures may cause permanent damage. Functional operation under these conditions is not permitted.
Recommended Operating Range
Symbol
Parameter
Conditions
Min.
Typ.
Max.
Units
V
DD
Operating Voltage
3.2
4.0
4.8
V
V
LCD
LCD Reference Voltage
2.5
3.0
3.5
V
T
AMB
Ambient Operating Temp. Range
-25
+70
C
f
OSC
Oscillator Frequency
32.768
kHz
DC Characteristics
Recommended operating conditions unless otherwise specified.
Symbol
Parameter
Conditions
Min.
Typ.*
Max.
Units
I
DD
Operating Supply Current
Unloaded
150
A
I
DD0
Idle Current
Idle mode, oscillator not running
1
A
V
33
Contrast Output Voltage at
COM1-4 and S1-2_n Pins
V
LCD
= 3.27V
Contrast voltage low
Contrast voltage middle
Contrast voltage high
2.83
2.97
3.09
V
V
V
V
IL
Input Low Voltage
V
SS
0.3 V
DD
V
V
IH
Input High Voltage
0.7 V
DD
V
DD
V
* Typical figures are at 25C and are for design aid only; not guaranteed and not subject to production testing.
Preliminary
AS2591
Rev. 1.0
Page 10
May 1999
Electrical Characteristics
Recommended operating conditions unless otherwise specified.
Symbol
Parameter
Conditions
Min.
Typ.
Max.
Units
F
LCD
LCD Frame Frequency
61
64
67
Hz
t
OFF-TIMER
Off Timer
4.75
5
5.25
sec
f
BLINK
Blinking Frequency
BF = 00
BF = 01
BF = 10
BF = 11
1.33
2.00
0.67
1.00
Hz
Hz
Hz
Hz
R
COM
Output Impedance of
Backplane Outputs
150
kohm
R
SEG
Output Impedance of
Segment Outputs
150
kohm
Package Outline
44 Pin TQFP
See Package Catalogue
Devices sold by Austria Mikro Systeme Int. AG are covered by the warranty and patent indemnification provisions appearing in
its Term of Sale. Austria Mikro Systeme Int. AG makes no warranty, express, statutory, implied, or by description regarding
the information set forth herein or regarding the freedom of the described devices from patent infringement Austria Mikro
Systeme Int. AG reserves the right to change specifications and prices at any time and without notice. Therefore, prior to
designing this product into a system, it is necessary to check with Austria Mikro Systeme Int. AG for current information. This
product is intended for use in normal commercial applications. Applications requiring extended temperature range, unusual
environmental requirements, or high reliability applications, such as military, medical life-support or life-sustaining equipment
are specifically not recommended without additional processing by Austria Mikro Systeme Int. AG for each application.
Copyright 1999, Austria Mikro Systeme International AG, Schloss Premsttten, 8141 Unterpremsttten, Austria.
Trademarks Registered. All rights reserved. The material herein may not be reproduced, adapted, merged, translated,
stored, or used without the prior written consent of the copyright owner.
Austria Mikro Systeme Int. AG reserves the right to change or discontinue this product without notice.
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