Preliminary Data Sheet
AS2507
Single Chip 2-Wire Intercom
CMOS Integrated Circuit
®
Austria Mikro Systeme International AG
Key Features
General Description
Line/speech circuit and signalling on one 14
The AS2507 is a CMOS integrated circuit that
contains all the functions needed to build a 2wire intercom network.
pin CMOS chip
Only 2 wires needed for power supply,
signalling and speech
Soft clipping to avoid harsh distortion
Fully integrated 2/4 wire conversion
Side tone cancellation
Low noise
Signalling with FSK modem
Low standby power consumption allows
parallel operation of up to 25 terminals on a
bus pair with central supply
Parallel operation of up to 70 terminals if
supplied locally
Controllable via simple µC interface
Very few external components
The device incorporates 2/4-wire conversion
(hybrid), soft clipping for high speech quality,
FSK modem and a simple interface to a
microcontroller.
The signalling mode is selectable between
FSK modulation and burst mode.
The low standby current (typ. 2 mA) allows
several devices to listen to the 2-wire line.
The speech circuit is designed for compatibility
with commonly used handset (150Ω earpiece
and electret microphone) with receive gain of
-6 dB and transmit gain of 32 dB (relative to
line).
Package
Application
Available in 14 pin DIP and 16 pin SOIC
Entrance telephone system, intercom and data
transmission, alarm systems, toy phone
Block Diagram
1/9
July 1998
Preliminary Data Sheet
AS2507
Pin description
Pin #
DIP 14
Pin #
SO 16
Symbol
7
7
M1
Function
Microphone Input 1
Differential input for the microphone (electret)
6
6
M2
Microphone Input 2
Differential input for the microphone (electret)
2
2
RI
Receive Input
Input for ac-separated receive signal
4
4
RO
Receive Output to Handset
Output for driving a dynamic earpiece with an impedance from 150Ω to
300Ω
14
15
16
VDD
Voltage Drain Drain
Positive Power Supply
9
9
10
VSS
Voltage Source Source
8
AGND
8
Negative Power Supply
Analogue Ground
Signal ground for the internal amplifiers
11
12
OSC1
Oscillator Output 1
Output to ceramic resonator 3.58MHz.
12
13
OSC2
Oscillator Input 2
Input for ceramic resonator 3.58MHz.
5
5
PD
Power Down Input
Active high, i.e. a high level on this pin will power down the analogue
signal path.
10
11
RxD
Receive Data Output
Output of the FSK demodulator
13
14
TxD
Transmit Data Input
Input for the FSK modulator
1
1
TE
Transmit Enable
Input for enabling transmit data
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July 1998
Preliminary Data Sheet
AS2507
FSK Modulator
Two signalling modes are provided, namely
FSK and burst mode. The signalling mode and
the signalling can be controlled by a
microcontroller using the TE and TXD inputs
as follows:
Functional Description
The AS2507 is a CMOS integrated circuit that
incorporates a speech circuit and a FSK
modem. It is intended to be used as linepowered interface on a 2-wire intercom bus.
TE
0
0
1
1
Standby Condition
During standby operation (PD=High) only the
FSK demodulator is active to provide the
companion microcontroller with all signalling
information on the 2-wire bus. The low power
consumption (typical 2mA) and a high input
and output impedance in standby mode allow
the parallel operation of many terminals on
each bus pair.
TXD
0
1
0
1
MODE
IDLE, no transmission
TEST, for testing only
SPACE ("0") 18.645 kHz
MARK ("1") 22.375 kHz
FSK Demodulator
Also the demodulator provides two modes for
detection as follows:
Signal on line
IDLE, no transmission
SPACE ("0") 18.645 kHz
MARK ("1") 22.375 kHz
2/4-Wire Conversion
The AS2507 has a built-in side tone
cancellation circuit. The transmit signal is
attenuated by 6 dB over the 600Ω resistor (ac
impedance) and subtracted from the receive
signal at the receive input (RI). This
configuration allows the selection of the
required ac impedance and yet maintaining a
good side tone cancellation.
RXD
1
0
1
The demodulator consists out of a bandpass
filter to attenuate interfering speech signals
and a period counter. The RxD output is
updated after each valid period or a counter
overflow.
AC Impedance
The ac impedance is determined by an
external resistor at the TO output (typical
600Ω).
Transmission Protocol
In order to assure a safe data transmission,
data framing is recommended. Each frame
should consist out of a preamble (e.g. FFhex),
a header (e.g. AAhex), data bytes and
checksum.
Transmit Path
The gain of the transmit path from the
microphone inputs (M1/M2) to the transmit
output (TO) is set to 32 dB. The soft clip level
is set to 0.5VPEAK at TO. In standby the output
impedance is 60kΩ.
Independence of bus polarity
Centrally supplied terminals can be connected
to the 2-wire bus independent from polarity. In
this case a rectifier bridge, known from
telephony, is recommended since the DCsupply current will bias the diodes.
Receive Path
The gain of the receive path from the receive
input (RI) to the receive output (RO) is set to
-6dB. The receive input is internally biased to
AGND with a 500kΩ resistor.
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July 1998
Preliminary Data Sheet
AS2507
Typical 2-Wire Intercom Application
4/9
July 1998
Preliminary Data Sheet
AS2507
Electrical characteristics
Electrical charateristics are measured with the Test Circuit application. Typical mean values will not be
tested.
Absolute maximum ratings
Positive Supply Voltage
-0.3V <= VDD <= 7V
Input Current
± 25mA
Analogue Input Voltage
-0.3V <= Vin <= VDD+0.3V
Digital Input Voltage
-0.3V <= Vin <= VDD+0.3V
± 1000V
Electrostatic Discharge (HBM 1.5kΩ-100pF)
Storage Temperature
-65°C to +125°C
Recommended operating conditions
Supply Voltage (VDD)
5V ±10%
Oscillator Frequency
3.58 MHz
Operating Temperature
-10°C to +60°C
DC characteristics
VDD=5V, f=1kHz, unless other specified
Symbol Parameter
Conditions
IDDS
Supply Current
IDDO
Supply Current
VIL
Digital Input Voltage LOW
VIH
Digital Input Voltage HIGH
Min
Typ
Max
Units
Standby Mode
PD=High, VDD=2.5V
2
3
mA
Operating Mode
PD=Low, VDD=2.5V
5
6
mA
VSS
0.1 VDD
V
0.9 VDD
VDD
V
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July 1998
Preliminary Data Sheet
AS2507
Transmit characteristics
VDD=5V, f=1kHz, unless other specified
Symbol Parameter
Conditions
ATX
Transmit Gain
M1/M2 —> TO
VTO=0.25VRMS
THD
Distortion
VTO=0.25VRMS
VNO
Noise Output Voltage
TO
TAMP=25°C
VAGC1
Soft Clip Level
M1/M2 —> TO at TO
Zout-TO
Output Impedance with
PD=High at TO
Min
Typ
Max
Units
+30.0
+32.0
+34.0
dB
2
%
-60
dBmp
0.5
PD=High
TAMP=25°C
VP
60
kΩ
Receive characteristics
VDD=5V, f=1kHz, unless other specified
Symbol Parameter
Conditions
Min
Typ
Max
Units
ARX
Receive Gain
RI —> RO
VRI=0.25VRMS
-8.0
-6.0
-4.0
dB
THD
Distortion
VRI=0.25VRMS
2
%
VNO
Noise Output Voltage
RO
TAMP=25°C
-60
dBmp
ST
Sidetone
VRI=0.25VRMS
ZIn-RI
Input Impedance
RI
6/9
24
dB
500
kΩ
July 1998
Preliminary Data Sheet
AS2507
FSK characteristics
VDD=5V, f=1kHz, unless other specified
Symbol Parameter
Conditions
Min
Typ
Max
fMARK
MARK Frequency
TE=High
TxD=High
fOSC=3.579545MHz
22375
Hz
fSPACE
SPACE Frequency
TE=High
TxD=Low
fOSC=3.579545MHz
18645
Hz
f∆MARK
Valid input frequency
range MARK
TE=Low
22375
±447
Hz
f∆SPACE Valid input frequency
range SPACE
TE=Low
18645
±372
Hz
VRImin
Minimum Receive Input
Voltage Detection Level
TE=Low
VTO
Tone Output Level
TE=High
AVB
Attenuation at 4kHz
Input Bandpass Filter
100
600
Units
mVp
mVp
35
dB
Test circuit
7/9
July 1998
Preliminary Data Sheet
AS2507
Packaging
The device is available in the packages outlined below (not to scale). For exact mechanical package
dimensions please see AMSAG packaging information.
14-pin plastic DIP (suffix P)
16-pin plastic SOICw (suffix T)
Max. Body Length
Max. Body Width
Pitch
Max. Body Length
Max. Body Width
Pitch
10.5mm / 414mil
7.6mm / 300mil
1.27mm / 50mil
20.19mm / 795mil
7.11mm / 280mil
2.54mm / 100mil
Pin-out
DIP14 (suffix P)
1
2
3
4
5
6
7
–
–
–
–
–
–
–
TE
RI
TO
RO
PD
M1
M2
SO16w (suffix T)
VDD
TxD
OSC2
OSC1
RxD
VSS
AGND
–
–
–
–
–
–
–
14
13
12
11
10
9
8
1
2
3
4
5
6
7
8
–
–
–
–
–
–
–
–
TE
RI
TO
RO
PD
M1
M2
AGND
VDD
VDD
TxD
OSC2
OSC1
RxD
VSS
VSS
–
–
–
–
–
–
–
–
16
15
14
13
12
11
10
9
Marking
YYWWAAA
AS2507
Austria
YY
WW
AAA
year of production
calendar week of production
AMSAG assembly ID
8/9
July 1998
Preliminary Data Sheet
AS2507
Ordering information
Number
Package
Description
AS2507 P
AS2507 T
DIP14
SO16w
plastic dual inline package - 14 leads (suffix P)
plastic small outline package - 16 leads (suffix T)
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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 decribed 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 equiment are specifically not
recommended without additional processing by Austria Mikro Systeme Int. AG for each application.
Copyright © 1997-98, Austria Mikro Systeme International Int. AG, Schloss Premstaetten, 8141 Unterpremstaetten, AustriaEurope. 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.
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Austria Mikro Systeme International Int. AG
Schloß Premstätten
8141 Unterpremstätten, Austria-Europe
Tel: +43 (0)3136 500-0
Fax: +43 (0)3136 52501, 53650
email: [email protected]
http://www.vertical-global.com
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Application support
Please contact your local sales office or your distributor
9/9
July 1998