austriamicrosystems
Multi-Standard CMOS Telephone IC
for Basic Telephones
AS2533-36
DATA SHEET
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.
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.
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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)
Dialler
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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
Ringer
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-
-
-
-
Key Features
Line Interface and Speech Circuit
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-
-
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
Block Diagram
Figure 1 Block Diagram
Revision 8.8
Page 1 of 25
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
This is the analogue ground for the amplifiers.
6
STB
S
ide
T
one
B
alance Input
This is the input for side tone cancellation.
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
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
SMD
Lead
12
MODE
Signaling
MODE
Select Input
Function
Dialing inhibited
LD mode, 10 pps, 33/66 ms
LD mode, 10 pps, 40/60 ms
LD mode, 20 pps, 33/66 ms
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
MF only, 82/160 ms
Mode pin
Open
Row 1
Row 2
Row 3
Row 4
Row 5
Row 61
Row 7
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)
Revision 8.8
Page 2 of 25
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
This is a Schmitt trigger input for ring frequency discrimination. Disabled during off-hook.
22
LED
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).
23
24
25
M1
M2
CS
C
urrent
S
hunt Control Output
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.
26
27
V
SS
LI
Negative Power Supply
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
This is the input for sensing the line current.
2
MFL
MF L
evel Setting
A voltage divider connected from this pin to A
GND
and V
SS
can be used to set the DTMF level.
3
RO
R
eceive
O
utput
This is the output for driving a dynamic earpiece with an impedance of 150 to 300
Ω.
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
AS2533
4
10
yes
yes
yes
yes
P/M
yes
yes
yes
yes
yes
AS2534/34R
AS2535
AS2536
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).
Revision 8.8
Page 3 of 25
Data Sheet AS2533-36
austriamicrosystems
Functional Description
Keyboard Connections
Key closure, R
ON
max. = 1 kΩ
Key open, R
OFF
min. = 1 MΩ
(Either
VOL
or
+/–
keys)
C1
R1
R2
R3
R4
P /
/
M
P M
4
4
8
8
#
#
LNR
LNR
A
A
RP
RP
M2
M2
C2
1
1
5
5
9
9
R1
R1
VOL
VOL
B
B
PS
PS
M3
M3
C3
2
2
6
6
0
0
R2
R2
+
+
C
C
T /
/
P
T P
M4
M4
C4
3
3
7
7
*
*
R3
R3
−
−
D
D
M1
M1
MR
MR
Figure 2 Keyboard Connection AS2533/36
C1
R1
R2
R3
R4
P /
/
M
P M
4
4
8
8
#
#
LNR
LNR
A
A
RP
RP
C2
1
1
5
5
9
9
R1
R1
VOL
VOL
B
B
PS
PS
C3
2
2
6
6
0
0
R2
R2
+
+
C
C
T /
/
P
T P
C4
3
3
7
7
*
*
R3
R3
−
−
D
D
Figure 3 Keyboard Connection AS2534
Revision 8.8
Page 4 of 25
Data Sheet AS2533-36
austriamicrosystems
(either
VOL
or
+/–
keys)
Keyboard Connections continued
C1
R1
R2
R3
R4
P /
/
M
P M
4
4
8
8
#
#
LNR
LNR
M1
M1
M5
M5
M9
M9
C2
1
1
5
5
9
9
R1
R1
VOL
VOL
M2
M2
M6
M6
M 10
M 10
C3
2
2
6
6
0
0
R2
R2
+
+
M3
M3
M7
M7
M 11
M 11
C4
3
3
7
7
*
*
R3
R3
−
−
M4
M4
M8
M8
M 12
M 12
Figure 4 Keyboard Connection AS2535
Power On Reset
The on chip power on reset circuit monitors the supply
voltage (V
DD
) during off-hook. When V
DD
rises above
approx. 1.2V, a power on reset occurs which clears the
RAM.
During pulse dialing the speech circuit and other part of
the device not operating is in a power down mode to save
current. The CS pin is pulled to V
SS
in order to turn the
external shunt transistor on to keep a low voltage drop at
the LS pin during make periods.
DC Conditions
The normal operating range is from 13 mA to 100 mA.
Operating range with reduced performance is from 5 mA to
13 mA (parallel operation). In the operating range all
functions are operational.
At line currents below 13 mA the AS253x provides an
additional slope below 4.5V in order to allow parallel
operation (see Figure 12).
The dc characteristic (excluding diode bridge) is
determined by the voltage at LI and the resistor R1 at line
currents above 13 mA as follows:
VLS = VLI + ILINE × R1
The voltage at LI is 4.5V in the normal operating range.
AC Impedance
The ac impedance of the circuit is set by external
components. The impedance can be real or complex.
The ac impedance is determined as follows:
ZAC = 33 · Z1
The dc value of Z1 should be 30
Ω
to maintain correct dc
performance.
Return loss and side tone cancellation can be determined
independent of each other.
Speech Circuit
The speech circuit consists of a transmit and a receive
path with dual soft clipping, mute, line loss compensation
and sidetone cancellation.
Revision 8.8
Page 5 of 25
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