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austriamicrosystems
Multi-Standard CMOS Telephone IC
for Basic Telephones
AS2533-36
General Description
The AS253x is a CMOS integrated circuit that contains all
the functions needed to build a high performance electronic
telephone set with basic features.
The AS253x incorporates a line interface, a speech circuit,
a dialler and ringer. It is a real single-chip / single-die IC
with 28 pins. It allows either package mounting or chip-on-
board mounting.
The device is available in 4 versions (pin-compatible) with
different features ranging from LNR only (last number
redial) to 4 direct (one-touch) memories and 10 indirect
(two-touch) memories. The sliding cursor procedure makes
the LNR function easy to use under various PABX systems.
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DATA SHEET
Dialler
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-
-
-
-
-
-
-
-
The versatility of the circuit is provided by pin options and a
few external components. This allows fast time-to-market
and easy adaptation to different PTT requirements. A
unique EMI performance has been achieved due to the
consequent use of CMOS amplifiers.
Key Features
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Line Interface and Speech Circuit
Block Diagram
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Ringer
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-
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LD/MF dialing and mixed-mode dialing
31 digit last number redial (LNR)
4 direct/10 indirect (AS2533/36), 12 direct (AS2535)
Repeat dialing by busy or engaged (not AS2535)
Confidence tone during memory programming and mute
Notepad memory function
Pause key for access pause or wait function
3 flash timings, 100 ms, 280 ms and 375/600 ms
Sliding cursor protocol with comparison
Electronic Rx volume control
Electronic microphone mute
Microphone amplifier with symmetrical input
Ring frequency discrimination
3-tone melody generator
Ring melody selection via keyboard
Ring volume selection via keyboard
Version available with fixed ring melody and ring volume
Package
-
SOIC 28 or DIE
Figure 1 Block Diagram
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Rx and Tx soft clipping to avoid harsh distortion
Real or complex impedance (EU compliant)
Stabilized supply for dialler and peripherals
Automatic line loss compensation
Operating range from 13 to 100 mA (down to 5 mA with
reduced performance)
Unique EMI performance (EU compliant)
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Data Sheet AS2533-36
austriamicrosystems
Pin Description
Pin #
4
5
Symbol
V
DD
A
GND
Positive Voltage Supply
This is the supply pin for the circuit.
Function
A
nalog
G
round
S
ide
T
one
B
alance Input
This is the input for side tone cancellation.
6
STB
7
CI
C
omplex
I
mpedance Pin
For complex impedance a capacitor should be connected to
8
MO
M
elody
O
utput
PDM output of the melody generator for tone ringing with internal open-drain transistor.
Hi-Z when not active.
9
LLC
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L
ine
L
oss
C
ompensation
Select pin for line loss compensation (see also Figure 6 and Figure 7).
LLC = A
GND
: 20 - 50 mA LLC = V
DD
: 45 - 75 mA LLC = V
SS
: none.
10
HS/DP
H
ook
S
witch Input and
D
ial
P
ulse Output
This is an I/O that is pulled high by the hook switch when off-hook and an open drain pulls it low
during break periods of pulse dialing and flash.
11
OSC
OSC
illator Input
Pin for ceramic resonator (3.58 MHz).
Reference: Murata CSTCC3M58GD3346-R0
Murata CSTLS3M58GD3458-B0
Signaling
SMD
Lead
12
MODE
MODE
Select Input
Function
Mode pin
Open
Dialing inhibited
Row 1
Row 2
Row 3
LD mode, 10 pps, 33/66 ms
LD mode, 10 pps, 40/60 ms
LD mode, 20 pps, 33/66 ms
Row 4
Row 5
LD mode, 20 pps, 40/60 ms
LD mode, 10 pps, 33/66 ms, Temp. MF with tone on first * key entry
MF only, 82/82 ms
Row 61
Row 7
MF only, 82/160 ms
During temporary MF: 82/160 ms
13
14
15
16
C4
C3
C2
C1
Keyboard Columns
(see key arrangements in Figure 2, Figure 3 and Figure 4)
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This is the analogue ground for the amplifiers.
Data Sheet AS2533-36
austriamicrosystems
Pin #
17
18
19
20
21
Symbol
R4
R3
R2
R1
FCI
Function
Keyboard Rows
(see key arrangements in Figure 2, Figure 3 and Figure 4)
F
requency
C
omparator
I
nput
LED
Output Driver
Output for driving an LED that will be flashing when in Program/Mute state.
Microphone Inputs
Differential inputs for the microphone (electret).
22
LED
23
24
25
M1
M2
CS
C
urrent
S
hunt Control Output
Selection Overview
Function
Direct memories (one-key)
Indirect memories (two-key)
Repeat dialing
LNR key
Pause insertion by LNR key
Pause (PS) key
P/M or MT key
Tone/Pulse (T/P) key
Temporary MF by * key
Centrex (A - D) keys
Volume (VOL, –/+) keys
Volume reset by off-hook
Programming of tone ringer
0
12
4
0
0
10
yes
no
yes
yes
yes
yes
yes
yes
yes
yes
no
yes
P/M
P/M
P/M
yes
no
yes
yes
yes
yes
yes
no
yes
yes
yes
yes
no
yes
no
AS2534:yes
yes
yes
yes
AS2534R: no
R3 Flash duration
600 ms
600 ms
600 ms
600 ms
The corresponding product (AS2533-36) can be selected via bond-options (see chapter “Bond options” for details).
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27
V
SS
LI
Negative Power Supply
This N-channel open drain output controls the external high power shunt transistor for the modulation
of the line voltage and for shorting the line during make period of pulse dialing.
L
ine
I
nput
This input is used for power extraction and line current sensing.
28
RI
R
eceive
I
nput
This is the input for the receive signal.
1
LS
L
ine Current
S
ense Input
MF L
evel Setting
R
eceive
O
utput
This is the input for sensing the line current.
2
MFL
A voltage divider connected from this pin to A
GND
and V
SS
can be used to set the DTMF level.
3
RO
This is the output for driving a dynamic earpiece with an impedance of 150 to 300
Ω.
AS2533
4
10
yes
yes
yes
yes
P/M
yes
yes
yes
yes
yes
AS2534/34R
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AS2535
AS2536
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This is a Schmitt trigger input for ring frequency discrimination. Disabled during off-hook.
Data Sheet AS2533-36
austriamicrosystems
Functional Description
Keyboard Connections
Key closure, R
ON
max. = 1 kΩ
Key open, R
OF F
min. = 1 MΩ
(Either
VOL
or
+/–
keys)
C1
R1
R2
R3
R4
P /
/
M
P M
4
4
8
8
#
#
C2
1
1
5
5
9
9
R1
R1
C3
2
2
6
6
0
0
R2
R2
+
+
C4
3
3
7
7
*
*
R3
R3
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LN R
LN R
A
A
VO L
VO L
B
B
−
−
D
D
C
C
RP
RP
PS
PS
T /
/
P
T P
M4
M4
M1
M1
M2
M2
M3
M3
MR
MR
Figure 2 Keyboard Connection AS2533/36
C1
C2
1
1
5
5
9
9
C3
2
2
6
6
0
0
C4
3
3
7
7
R1
R2
R3
R4
P /
/
M
P M
4
4
8
8
#
#
*
*
R1
R1
R2
R2
+
+
R3
R3
LN R
LN R
A
A
RP
RP
VO L
VO L
B
B
PS
PS
−
−
D
D
C
C
T /
/
P
T P
Figure 3 Keyboard Connection AS2534
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