austriamicrosystems AG
is now
ams AG
The technical content of this austriamicrosystems datasheet is still valid.
Contact information:
Headquarters:
ams AG
Tobelbaderstrasse 30
8141 Unterpremstaetten, Austria
Tel: +43 (0) 3136 500 0
e-Mail:
ams_sales@ams.com
Please visit our website at
www.ams.com
Data Sheet AS2540
austriamicrosystems
austriamicrosystems
DATA SHEET (PREL IMINA RY)
Remote Controlled Single-Chip-Telephone
AS2540
General Description
The AS2540 is a CMOS integrated circuit that
incorporates a speech circuit (line-adaptation, 2/4-wire
conversion, separate Rx- and Tx-amplifiers for handset
and modem), MF dialler, ring frequency detector, ring
melody generator and a two wire serial interface. It
shall act as an a/b-line-powered device in order to
interface a main-powered CPU to the analogue
telephone line.
AS2540 can operate in a so-called mainpower mode
and in a backup mode. During mainpower mode, a
watchdog timer is running on AS2540, which has to be
reset via the serial interface, which is connected to the
CPU through opto-couplers. During backup mode (=
The main-power failure or SW engine problem),
AS2540 can operate as an independent basic MF
dialler (digits 0-9*#)
Key Features
-
-
-
-
-
-
-
-
-
-
-
-
-
-
Applications
-
-
-
-
-
Block Diagram
Line
Te
Revision 3.1
c
h
ni
c
a
a
m
lc s
on A
te G
nt
st
il
Web Telephones
Answering Machines
Fax Machines
Base Station of Cordless Telephones
hones
ones
Hospital Communication Units
Line Interface, Speech Circuit, MF Dialler and Tone Ringer
on a 28 pin CMOS chip
Programmable via 2-wire serial interface
(UART 9600 baud, 8N1)
Watch dog timer for Backup Mode
Additional input for modem transmit path
Additional output for modem receive path
th
CMOS for high EMC immunity
Low Noise (max. –72 dBm)
Operating range from 15mA to 100mA (down to 5mA with
(do
(dow
reduced performance)
red
Soft clipping for handset operation to avoid harsh distortion
c
cl
set
av
a
Line loss compensation selectable by pin option
ine los
ation
n
b
Real and complex impedance selectable by external
an
mpedance se
pedance
com
components
S
Side tone adaption se
e
ption selectable by external components
Ring frequency discrim
quency discrimination
3-tone ring melody generator
-tone
e
Package
-
-
28 pin SOIC
Di
Dic
Dice-on-Foil
Main
Power
Mode
ain
M
+ 6dB
Backup Mode
LS
LI
Line
LS
LI
RI
SB
T
-2d B
ROH
ROT
M1
M2
T
IT
+ 2d B
RI
SB
T
-2dB
CS
S
CS
Mask
Mask
CI
CI
DPn
AGND
DPn
DT
MF-
generator
DT
MF-
g enerator
SMUT
E
S
MASK
S
MAS
K
SMUTE
SROH
SROH
SROT
S
DPn
S
DPn
Dia l
Dig it
Dial
Digit
ST
IT
SROT
ST
IT
RxD
DIALLER
C1
C2
C3
R1
R2
MODE
UART
T
xD
C1
C2
C3
R1
R2
MODE
VDD
DIALLER
RFD
MO
EHS
MHS
VS
S
OSC
RFD
MO
EHS
MHS
VS
S
OS
C
lv
+ 6dB
+ 2d B
UART
al
ROH
ROT
M1
M2
T
IT
AGND
RxD
T
xD
VDD
id
Page 1 of 18
Data Sheet AS2540
austriamicrosystems
Pin Description
Pin #
15
Sym b o l
RFD
Fu n ctio n
R
ing
F
requency
D
iscrimination
Schmitt trigger input for ring frequency discrimination. Disabled during off-hook.
7
LS
L
ine Current
S
ense Input
5
LI
6
RI
2
STB
3
CS
8
CI
16
DPn
17
EHS
18
MHS
19
MODE
Te
c
h
n
28
MO
Ring
11
VDD
4
VSS
Revision 3.1
ic a
al m
c
o
s
A
nt G
en
ts
til
l
v
al
i
d
L
ine
I
nput
Input used for power extraction and line current sensing
Input for sensing the line current
R
eceive
I
nput
Input for ac-separated receive signal
S
ide
T
one
B
alance Input
Input for side tone cancellation network
C
urrent
S
hunt Control Output
N-channel open drain output to control the external high power shunt transist for synthesising ac- and
ntrol
we
unt transi
nt transistor
dc- impedance, modulation of line voltage and shorting the line during make periods of pulse dialling
ne
sh
du g ma
C
omplex
I
mpedance Input
D
ial
P
ulse Output
Input pin for the capacitor to progra a complex impedance
r program
ex mpedance
Open drain output pulls low during break periods of pulse dialling and flash
put
ut
d
reak
k
p
pu
E
lectronic
H
ook
S
witch
witc
M
anual
H
ook
S
witch
Schmitt Trigger Input to detect an electronic off-hook.
er Inp
tect n electro
Schmitt Trigger Input to detect a manual off-hook.
nput
put
ct m
D
TMF
L
evel
S
election
vel
-4/-6dBm
Bm
-6/-8dBm
8dBm
-8/-10dBm
dBm
—>
—
—>
—>
DLS open
DLS-r1
DLS-r2
L
ine
L
oss
C
ompensation Select Pin
in
45mA-
45mA-7
45mA-75mA
20mA-50mA
20m
None
N
—>
—>
—>
LLC open
LLC-r3
LLC-r4
M
elody
O
utput
PDM output of the ring melody generator.
V
oltage
D
rain
D
rain
Positive Power Supply
V
oltage
S
ource
S
ource
Negative Power Supply
Page 2 of 18
Data Sheet AS2540
austriamicrosystems
Fu n ctio n
Pin #
25
Sym b o l
OSC
O
scillator Input
Input for ceramic resonator 3.58MHz.
Recommended type: Murata CSA 3.58MG312AM or compatible
12
AGND
A
nalogue
G
round
Special ground for the internal amplifiers
Schmitt trigger input to serial interface
27
TXD
T
ransmit
D
ata Output
Open drain output from serial interface
Keyboard
Keyboard
20
21
22
23
24
10
R1
R2
C1
C2
C3
ROT
R
ows
C
olumns
R
eceive
O
utput to
T
ransformer
Output for driving a transformer with an ac impedance larger than 1
Ω
10kΩ
imp
er
1
TIT
T
ransformer
I
nput from
T
ransformer
ansfo
ansform
Single ended input for transformer
ransformer
9
ROH
R
eceive
O
utput to
H
andset
M
icrophone Inputs
e
ving dynam
ece
imped
Output for driving a dynami earpiece with an impedance from 150Ω to 300Ω
dynamic
13
14
M2
M1
Differential inputs for the microphone (ele
uts
e crophone (electret)
Te
Revision 3.1
ch
ni
ca
am
lc s
o
n A
te G
n
t
s
t
ill
Page 3 of 18
v
a
lid
26
RXD
R
eceive
D
ata Input
Data Sheet AS2540
austriamicrosystems
Functional Description
Modes of operation
There are 4 possible modes:
Example Main Power Mode
Line
LS
LI
+ 6dB
RI
ST
B
-2dB
+ 2dB
ROH
ROT
M1
M2
Idle Mode
Manual hook-switch and electronic hook-switch (e.g. relay)
is open (MHS
∩
EHS = logical 0), no ring signal is applied,
the oscillator is stopped, signalling via the serial interface
is not possible.
CS
Mask
T
IT
CI
DP
n
DT
MF-
generator
AGND
Ringing Mode
AS2540 is supplied via the ring capacitor and external
path, manual hook -switch and electronic hook-switch is
open (MHS
∩
EHS = logical 0), the oscillator is running, a
valid incoming ringing is signalled via the serial interface to
the CPU. If the CPU does not reply the AS2540 switches
into backup mode and sends a ring melody to the MO
output.
C1
C2
C3
R1
R2
DIALLER
am
lc s
on A
te G
nt
s
t
i
l
l
MODE
RFD
MO
O
EHS
HS
MHS
Backup Mode
Start-up in backu mode
rt-up backup
p
Manual hook-switch and/or electronic hook-switch is closed
ch close
(MHS
∪
EHS = logical 1), AS2540 is supplied with line
ed
d
current, the oscillator is running, the keyscan is enabled
scan enable
enab
and the handset path is switched on, signalling via the
serial interface is possible. After AS2540 has s
S2540
started
st
dialling in backup mode, he must not be interrupted any
ot
inte
more in order to ensure consistent dialling. A mode
lin
ode
transition BM -> MPM is only possible before AS2540 has
S2540
540
started dialling digits independently.
As soon as AS2540 is supplied with line current, the
oon
AS254
c
external V
dd
capacitor will be charged up via the LI and
ernal
d
ca
VDD pin and after the V
dd
voltage has reached the
an
operati
operatin level, the handset path of the speech circuit is
operating
switched on. This off-hook status is also signalled to the
sw
switc
iinternal logic via the MHS or EHS pin in order to start the
pinscan and subsequently set the country specific modes.
Additionally a <LineEvent> message is sent to the CPU.
Start-up in ring mode
Main Po wer Mode
Manual hook-switch and/or electronic hook-swit is
ectronic hook-swi
onic hook-switch
closed, AS2540 is supplied with line current (MHS
∪
EHS
d
curre
= logical 1), the oscillator is running, the keyscan is
ator s
disabled, AS2540 is controlled via th serial interface,
the
s ntrolled
handset path or monitor path or m
modem path is on,
r
signalling via the serial interfa is possible.
interface
a
T
e
c
h
Select Operation Mo
ct
eration Mode
Co m m an d Mes sag e
s
<SetHandse
<SetHandset
<SetHandsetPath>
<Se
<SetMode
<SetModemPath>
<SetM
<SetMonitorPath>
etM
Swit ch es ON
SROH
SROT & STIT
SROH & SROT
Swit ch es OFF
SROT & STIT
STIT
When a ringing signal is applied to the line, V
dd
of AS2540
is charged up via an external path. After V
dd
has reached
the operating voltage the oscillator starts and AS2540
discriminates the ring frequency. After a valid ring
frequency is applied on the RFD pin, the logic sends a
<LineEvent> message is sent to the CPU and a watchdog
timer is started. When the <LineEvent> message is not quit
by the CPU before the watchdog timer has finished the
countdown, AS2540 changes into backup mode and sends
out a melody via the MO pin.
ni
ca
DC conditions
The normal operating mode is from 15mA to 100mA. An
operating mode with reduced performance is from 5mA to
15mA. In the line hold range from 0mA to 5mA the device
is in a power down mode and the voltage at LI is reduced
to a maximum of 3.5V
Revision 3.1
v
a
l
SROH
SROT
ST
IT
S
MAS
K
S
DPn
Dial
Digit
SMUT
E
RxD
T
xD
UART
VDD
VS
S
OS
C
id
Page 4 of 18
京公网安备 11010802033920号
EEWORLD
