AS2523F AMSCO [austriamicrosystems AG], AS2523F Datasheet - Page 5

• Manufacturer Part Number: AS2523F
• Description: Telephone Line Interface and Speakerphone Circuit
• Manufacturer: AMSCO [austriamicrosystems AG]

Data Sheet AS2523, AS2524, AS2524B
Functional Description
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.
The DC characteristic is determined by the voltage at LI-
pin and a 30Ω resistor between LI- and LS-pin. It can be
calculated by the following equation: V
30Ω. V
2/4 wire conversion
AS2523/24 has built in two Wheatstone bridges 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.
AC-impedance
The AC-impedance of AS2523/24 is set to t.m. 1000Ω.
With the external capacitor at CI-pin it can be programmed
complex. With an external resistor of approx. 1.5kΩ
connected to the LS-pin it can be programmed to 600Ω.
Side Tone
A good side tone cancellation can be achieved by using the
following equation:
Z
Transmit path
The gain of the M1/M2 → LS is set to +37dB. This gain
can be changed by programming on AS2523 from +30dB to
+45dB in 1dB steps (Register Txgain), on AS2524 / 24B it
is set to +37dB per default. The input is differential with an
impedance of 10kΩ. The soft clip circuit limits the output
voltage at LS to 2V
Revision 1.13
BAL
/Z
LINE
LI
can be programmed to be 3.5V or 4.5V.
= 10
p.
There is LLC for this path.
LS
voice switching circuit
= V
TX_atten
RX
LI
+ I
Line
switching
Voice
*
speech
The gain of the M3/M4 → LS is set to +46dB.
This gain can be changed by programming from +39dB to
+54dB in 1dB steps on AS2523. The input is differential
with an impedance of 10kΩ. The soft clip circuit limits the
output voltage at LS to 2V
Receive path
The gain of the LS → RO receive path is set to +7.5dB.
This gain can be changed by programming from –7.5dB to
+7.5dB in 1dB steps (Register Rxgain). The receive input
is the differential signal of RI and STB. The soft clip circuit
limits the output voltage at RO to 1V
distortion and acoustic shock. There is LLC for this path.
The gain of the LS → LO receive path is set to +32dB.
This gain can be changed by programming from +19dB to -
34dB in 1dB steps. The user can also change the gain via
Register Handsfree receive end gain (See section
"Handsfree"). The receive input is the differential signal of
RI and STB. The soft clip circuit limits the output voltage at
LO to 1.1V
shock. There is optional LLC for this path.
Line Loss Compensation (AS2523, AS2524B)
-
-
-
When it is activated, the transmit and receive gains for
both I/O’s are decreased by 6dB at line currents from
20mA to 50mA or from 45mA to 75mA.
Handsfree
The handsfree function allows voice communication without
using the handset (full 2-way speaker phone). Two voice
controlled attenuators prevent acoustic coupling between
the loudspeaker and the microphone. The voice switching
circuit has three states, namely idle, transmit or receive. In
receive mode the attenuation of the receive path and the
transmit path can be controlled by Register Handsfree
receive end gain between 0dB and -20dB. The following
table shows how voice switching is controlled
Backgnd
monitor
programmable on AS2523
not activated at AS2524
permanently activated at AS2524B
noise
p.
It prevents harsh distortion and acoustic
austriamicrosystems
p
. There is no LLC for this path.
p.
It prevents harsh
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