Datasheet AS2507P, AS2507T Datasheet (Austria Mikro Systeme International)

Preliminary Data Sheet AS2507

Single Chip 2-Wire Intercom

Austria Mikro Systeme International AG

®

Key Features



Line/speech circuit and s ign alli ng on o ne 14
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 term inals 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

Application

CMOS Integrated Circuit

General Description

The AS2507 is a CMOS integrated circuit that
contains all the func tions needed to build a 2­wire intercom network.

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 design ed for c ompatibi lit y
with commonly used handset (150 Ω earpiece
and electret microphone) with receive gain of

-6 dB and transmit gain of 32 dB (relative to
line).

Package

Entrance telephone s ystem , intercom and data
transmission, alarm systems, toy phone

Block Diagram

Available in 14 pin DIP and 16 pin SOIC

1/9 July 1998

Preliminary Data Sheet AS2507

Pin description

Pin #

DIP 14

14 15

11 12 OSC1

Pin #

SO 16

77 M1

66 M2

22 RI

44 RO

16

9910VSS

88AGND

Symbol Function

VDD

Microphone Input 1

Differential input for the microphone (electret)

Microphone Input 2

Differential input for the microphone (electret)

Receive Input

Input for ac-separated receive signal

Receive Output to Handset

Output for driving a dynamic earpiece with an impedance from 150Ω to
300Ω

Voltage Drain Drain

Positive Power Suppl y

Voltage Source Source

Negative Power Supply

Analogue Ground

Signal ground for the internal amplifiers

Oscillator Output 1

Output to ceramic resonator 3.58MHz.

12 13 OSC2

55 PD

10 11 RxD

13 14 TxD

11 TE

Oscillator Input 2

Input for ceramic resonator 3.58MHz.

Power Down Input

Active high, i.e. a high level on this pin will power down the analogue
signal path.

Receive Data Output

Output of the FSK demodulator

Transmit Data Input

Input for the FSK modulator

Transmit Enable

Input for enabling transmit data

2/9 July 1998

Preliminary Data Sheet AS2507

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.

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.

2/4-Wire Conversion

The AS2507 has a built-in side tone
cancellation circuit. The transmit signal is
attenuated by 6 dB over t he 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.

FSK Modulator

Two signalling modes are provided, namely
FSK and burst mode. T he signal ling m ode and
the signalling can be controlled by a
microcontroller using the TE and TXD inputs
as follows:

TE

TXD MODE

0 0 IDLE, no transmission
0 1 TEST, for testing only
1 0 SPACE ("0") 18.645 kHz
1 1 MARK ("1") 22.375 kHz

FSK Demodulator

Also the demodulat or provides two modes f or
detection as follows:

Signal on line

RXD

IDLE, no transmission 1
SPACE ("0") 18.645 kHz 0
MARK ("1") 22.375 kHz 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).

Transmit Path

The gain of the transmit path from the
microphone inputs (M1/M2) to the transmit
output (TO) is s et to 32 dB. The soft clip level
is set to 0.5V

PEAK

at TO. In standb y the output

impedance is 60kΩ.

Receive Path

The gain of the receive p ath from the receive
input (RI) to the receive output (RO) is set to

-6dB. The receive inpu t is internally biased to

GND

with a 500kΩ resistor.

A

Transmission Protocol

In order to assure a safe data transmission,
data framing is recommended. Each frame
should consist out of a pream ble (e.g. FF
a header (e.g. AA

hex

), data bytes and

hex

checksum.

Independence of bus polarity

Centrally supplied ter minals can be co nnected
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.

),

3/9 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 <= V

DD

<= 7V
Input Current ± 25mA
Analogue Input Voltage -0.3V <= Vin <= VDD+0.3V
Digital Input Voltage -0.3V <= Vin <= VDD+0.3V
Electrostatic Discharge (HBM 1.5kΩ-100pF)

± 1000V

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 Min Typ Max Units

DDS

I

DDO

I

V
V

IL
IH

Supply Current Standby Mode

DD

PD=High, V

=2.5V

Supply Current Operating Mode

PD=Low, V

DD

=2.5V
Digital Input Voltage LOW V
Digital Input Voltage HIGH 0.9 V

SS

DD

23mA

56mA

DD

0.1 V

DD

V

V
V

5/9 July 1998

Preliminary Data Sheet AS2507

Transmit characteristics

VDD=5V, f=1kHz, unless other specified
Symbol Parameter Conditions Min Typ Max Units

TX

A

Transmit Gain

VTO=0.25V

RMS

+30.0 +32.0 +34.0 dB

M1/M2 —> TO

THD Distortion VTO=0.25V

NO

V

Noise Output Voltage

T

AMP

RMS

2%

=25°C -60 dBmp

TO

AGC1

V

Soft Clip Level

0.5 V

P

M1/M2 —> TO at TO

out-TO

Z

Output Impedance with
PD=High at TO

PD=High

AMP

T

=25°C

60

kΩ

Receive characteristics

VDD=5V, f=1kHz, unless other specified
Symbol Parameter Conditions Min Typ Max Units

RX

A

Receive Gain

VRI=0.25V

RMS

-8.0 -6.0 -4.0 dB

RI —> RO

THD Distortion VRI=0.25V

RMS

2%

NO

V

Noise Output Voltage

AMP

T

=25°C -60 dBmp

RO

ST Sidetone VRI=0.25V

In-RI

Z

Input Impedance
RI

RMS

24 dB

500

kΩ

6/9 July 1998

Preliminary Data Sheet AS2507

FSK characteristics

VDD=5V, f=1kHz, unless other specified
Symbol Parameter Conditions Min Typ Max Units

MARK

f

MARK Frequency TE=High

22375 Hz

TxD=High

OSC

f

=3.579545MHz

SPACE

f

f∆

MARK

SPACE Frequency TE=High

Valid input frequency
range MARK

SPACE

f∆

Valid input frequency
range SPACE

RImin

V

Minimum Receive Inp ut
Voltage Detection Level

TO

V

VB

A

Tone Output Level TE=High 600 mVp
Attenuation at 4kHz

Input Bandpass Filter

Test circuit

18645 Hz

TxD=Low

OSC

f

=3.579545MHz

TE=Low 22375

Hz

±447

TE=Low 18645

Hz

±372

TE=Low 100 mVp

35 dB

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 AMS

AG

packaging inform ation.

14-pin plastic DIP (suffix P)

Max. Body Length 20.19mm / 795mil
Max. Body Width 7.11mm / 280mil
Pitch 2.54mm / 100mil

Pin-out

DIP14 (suffix P)

16-pin plastic SOICw (suffix T)

Max. Body Length 10.5mm / 414mil
Max. Body Width 7.6mm / 300mil
Pitch 1.27mm / 50mil

SO16w (suffix T)

1–TE VDD–14
2–RI TxD–13
3–TO OSC2–12
4 – RO OSC1 – 11
5–PD RxD–10
6–M1 VSS–9
7–M2 A

GND

–8

Marking

YYWWAAA
AS2507
Austria

YY year of produc tion
WW calendar week of production
AAA AMS

AG

assembly ID

1–TE VDD–16
2–RI VDD–15
3 – TO TxD – 14
4 – RO OSC2 – 13
5–PD OSC1–12
6 – M1 RxD – 11
7–M2 VSS–10
8–A

GND

VSS–9

8/9 July 1998

Preliminary Data Sheet AS2507

Ordering information

Number Package Description
AS2507 P DIP14

AS2507 T SO16w

Devices sold by Austria Mikro Systeme Int. AG are covered by the warranty and patent i demnification provisions appearing in its
Term of Sale. Austria Mikro Systeme Int. AG makes no warranty, express, st atut ory, implied, or by description regarding the
information set forth herein or regarding the freedom of the decribed devices from patent infringement. Austri a Mikro Systeme
Int. AG reserves the right to change specifications and prices at any t ime and without notice. Therefore, prior to designing this
product into a system, it is necessary to check with Austria Mikro S yst eme Int . AG f or current i nformation. This product is
intended for use in normal commercial applications. Applications requiring extended t em perature 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 Aust ri a Mikro Syst em e Int. AG for each application.

Copyright © 1997-98, Austria Mikro Systeme Internat ional Int. AG, Schloss Premstaetten, 8141 Unterpremstaetten, Aust ria­Europe. Trademarks Registered ®. All rights reserved. The mat eri al herein may not be reproduced, adapted, merged,
translated, stored, or used without the prior written consent of the copyright owner.

The information furnished here by Austria Mikro Systeme Int. AG is believed t o be correct and accurate. However, Austria Mikro
Systeme Int. AG shall not be liable to recipient or any third party for any damages, including but not limited to personal injury,
property damage, loss of profits, loss of use, interruption of business or indirect, special, incidental or consequenti al damages,
of any kind, in connection with or arising out of the furnishing, perform ance or use of the technical data herein. No obligation or
liability to recipient or any third party shall arise or flow out of Austria Mikro Systeme Int. AG rendering of technical or other
services.

plastic dual inline package - 14 leads (suffix P)
plastic small outline package - 16 leads (suffix T)

Headquarters

Austria Mikro Systeme International Int. AG

Schloß Premstätten
8141 Unterpremstätten, Austria-Europe
Tel: [phone]
Fax: [phone], 53650
email: info@vertical-global.c om
http://www.vertical-global. com

France

124 Avenue de Paris
F-94300 Vincennes
Tel:[phone]
Fax: [phone]

Italy

Piazzale Lugano 9
I-20158 Milano
Tel: [phone]
Fax: [phone]

USA

Suite 460
20863 Stevens Creek Blvd.
Cupertino, CA 95014
Tel: [phone]
Fax: [phone]

Germany (south)

Stefan-George-Ring 19
D-81929 München
Tel: [phone]
Fax: [phone]

Spain

Parc Te cnològic del Vallès
E-08290 Cerdanyola/Barcelona
Tel: [phone]
Fax: [phone]

Germany (nord)

Am Seestern 8
D-40547 Düsseldorf
Tel: [phone]
Fax: [phone]

Sweden (Scandinavia)

Sjöängsvägen 7
S-19272 Sollentuna
Stockholm
Tel: [phone]
Fax: [phone]

Hong Kong

21/F., 1 Des Voeux Road West
Sheung Wan, Hong Kong
Tel: [phone]
Fax: [phone]

United Kingdom

Coliseum Business Centre
Watchmoor Park
Camberley, Surrey
England GU15 3YL
Tel: [phone]
Fax: [phone]

Austria Mikro Systeme Int. AG is represented by distributors in the following countries. Please contact
your nearest regional sales office for the distributor’s address:

China, India, Japan, Korea, Singapore, Taiwan

Application support

Please contact your local sales off ic e or your distributor

9/9 July 1998