AS2540Q AMSCO [austriamicrosystems AG], AS2540Q Datasheet - Page 5

• Manufacturer Part Number: AS2540Q
• Description: Remote Controlled Single-Chip-Telephone
• Manufacturer: AMSCO [austriamicrosystems AG]

Data Sheet AS2540
The DC characteristic is determined by the voltage at LI
pin and a 30
calculated by the following equation: V
30 . The t.m. voltage at the LI pin is 4.5V. The calculation
leads to the following DC resistances: 330
currents from 15mA to 100mA.
2/4 wire conversion
AS2540 has a built-in dual Wheatstone bridge with one
common ground. This provides a maximum of
independence of AC impedance and side tone from each
other. One can adapt side tone without changing the AC
impedance.
A1=3.4/3.5
AC impedance
The ac impedance of AS2540 is set to t.m. 1000 . With
the external capacitor at CI pin it can be programmed
complex. With a parallel impedance at the LS pin it can be
programmed to 600 .
Side Tone
A good sidetone cancellation can be achieved by using the
following equation:
Z
Transmit path
The gain of the M1/M2 —> LS transmit path is set to 38dB
for ac-impedance 1000 . The input is differential with an
impedance of 25k . The soft clip circuit limits the output
voltage at LS to 2V
decay time is 20ms/6dB.
The gain of the TIT —> LS transmit path is set to 8dB for
ac-impedance 1000 . The input is single ended with an
impedance of 25k . The soft clip circuit is not active for
this input. The dynamic range of this path is 2.5Vp at LS.
Revision 3.1
BAL
/Z
LIN E
= 10
resistor between LI and LS pin. It can be
A2=-0.4
p.
The attack time is 30µs/6dB and the
LS
= V
LI
to 75
+ I
Line
at line
*
Receive path
The gain of the LS —> ROH receive path is set to 2dB for
ac-impedance 1000 . The receive input is the differential
signal of RI and STB. During DTMF dialling a MF comfort
tone is applied to ROH which is -30dB relative to the line
level. The soft clip circuit limits the output voltage at ROH
to 1V
The gain of the LS —> ROT receive path is set to 0dB for
ac-impedance 1000 . The receive input is the differential
signal of RI and STB. The soft clip circuit is not active for
this output.
Modescan
The DTMF-level on the line and the function of the line loss
compensation can be selected with the connection of the
MODE-pin to the keyboard matrix. The MODE-pin is
scanned once after each OFF-Hook transition.
X indicates connection to pin mode
C3
X
X
X
X
MODE
p.
PIN
It prevents harsh distortion and acoustic shock.
C2
X
X
X
X
C1
X
X
X
X
R2
R1
R2
X
austriamicrosystems
c1
R1
PIN
X
C1
1
4 5 6
7 8 9
* 0 #
C2
2 3
PIN
C2
45mA-75mA
45mA-75mA
45mA-75mA
20mA-50mA
20mA-50mA
20mA-50mA
No LLC
No LLC
No LLC
C3
LLC
PIN
C3
Dtmf Level
Page 5 of 18
-10dBm
-10dBm
-10dBm
-6dBm
-8dBm
-6dBm
-8dBm
-6dBm
-8dBm
PIN
PIN
R1
R2