tea1114auh NXP Semiconductors, tea1114auh Datasheet - Page 10

• Manufacturer Part Number: tea1114auh
• Description: Low Voltage Telephone Transmission Circuit With Dialler Interface And Regulated Strong Supply
• Manufacturer: NXP Semiconductors

Philips Semiconductors
Automatic gain control (pin AGC)
The TEA1114A performs automatic line loss
compensation. The automatic gain control varies the gain
of the microphone amplifier and the gain of the receive
amplifier in accordance with the DC line current.
The control range is 6.0 dB (which corresponds
approximately to a line length of 5 km for a 0.5 mm
diameter twisted-pair copper cable with a DC resistance of
176 /km and an average attenuation of 1.2 dB/km).
The IC can be used with different configurations of feeding
bridge (supply voltage and bridge resistance) by
connecting an external resistor R
AGC and V
currents to be increased (the ratio between I
not affected by the resistor). The AGC function is disabled
when pin AGC is left open-circuit.
Mute function (pin MUTE)
The mute function performs the switching between the
speech mode and the dialling mode.
When MUTE is LOW, the DTMF input is enabled and the
microphone and receive amplifier inputs are disabled.
In this mode, the DTMF tones are sent to the receive
output at a low level (confidence tone).
When MUTE is HIGH, the microphone and receiving
amplifiers inputs are enabled while the DTMF input is
disabled. The MUTE input is provided with an internal
pull-up current source to V
2000 Mar 21
Low voltage telephone transmission circuit with
dialler interface and regulated strong supply
EE
. This resistor enables the I
CC
.
AGC
between pins
start
start
and I
and I
stop
stop
line
is
10
Sidetone suppression
The TEA1114A anti-sidetone network comprising
R
suppresses the transmitted signal in the earpiece.
Maximum compensation is obtained when the following
conditions are fulfilled:
The scale factor k is chosen to meet the compatibility with
a standard capacitor from the E6 or E12 range for Z
In practice, Z
the line length. Therefore, the value of Z
average line length which gives satisfactory sidetone
suppression with short and long lines. The suppression
also depends on the accuracy of the match between Z
and the impedance of the average line.
The anti-sidetone network for the TEA1114A attenuates
the receiving signal from the line by 32 dB before it enters
the receiving amplifier. The attenuation is almost constant
over the whole audio frequency range.
A Wheatstone bridge configuration (see Fig.10) may also
be used.
More information on the balancing of an anti-sidetone
bridge can be obtained in our publication “Semiconductors
for Wired Telecom Systems; Application Handbook,
IC03b” . For ordering information please contact the Philips
Semiconductors sales office.
CC
R
k
Z
bal
SLPE
// Z
=
R
---------------------------------------------------------- -
=
line
ast2
k Z
, R
R
R
ast1
line
ast1
ast1
line
R
varies considerably with the line type and
, R
=
ast3
R
R
ast2
SLPE
+
CC
, R
R
SLPE
ast3
R
ast2
, R
SLPE
+
R
ast3
and Z
Product specification
TEA1114A
bal
should be for an
bal
(see Fig.9)
bal
.
bal