TEA7063 ST Microelectronics, Inc., TEA7063 Datasheet - Page 6

• Manufacturer Part Number: TEA7063
• Description: Speech Circuit With Power Management
• Manufacturer: ST Microelectronics, Inc.

TEA7063
2. TRANSMISSION CHAIN
2.1 A.G.C. In Transmission
The transmission gain between Microphone Input
(pin 7) and Vline (pin 16) is internally decreased
of 6dB when the line current varies from ILL to
ILS with a constant AC load of 600 .
The values of ILL (long line current) and ILS (short
line current) are programmable through I-start (pin
9) and I-slope (pin 15) (see also paragr. 4).
2.2 Sending Impedance
The impedance of the Output Stage Amplifier, Z
is determined by the impedance Z4 (at pin 3).
The total AC impedance shown to the line is the
parallel
Z
where:
Figure 3
6/15
par
= Z
out
//Z
int
//Z
Z
ext
out
= 10.65 xZ4
out
,
2.3 Sending Mute
In normal speech operation (V
0.8V), the signal at Microphone Input (pin 7) is
amplified to V
line) or 6dB lower (shorter lines) depending on
AGC control (see paragr. 4).
In sending mute condition (V 14 > 1.6V) these
gains are reduced of at least 60dB. In the same
condition, DTMF input (pin 6) is activated, with
gain Gmf to the line independent from I
2.4 Antisidetone Buffer
The signal coming from the sending preamplifier
is internally presented at pin 4 and than buffered
to pins 1 and 2 for sidetone cancellation (see
paragraph 3.2).
- Z
- Z
int
line
ext
= 10K //8.5 nF (internal)
= R6//C4 (at pin 16)
(pin 16) with the gain Gs (long
mute
at pin 14 <
line
lenght.