TEA1113 Philips Semiconductors, TEA1113 Datasheet - Page 6

• Manufacturer Part Number: TEA1113
• Description: Low voltage versatile telephone transmission circuit with dialler interface
• Manufacturer: Philips Semiconductors

Philips Semiconductors
The internal circuitry of the TEA1113 is supplied from
pin V
voltage by means of a resistor (R
decoupled by a capacitor C
supply peripheral circuits such as dialling or control
circuits. The V
consumed by the IC and the peripheral circuits as shown
by the formula (see also Figs 5 and 6). R
impedance of the voltage supply point, and I
current consumed by the output stage of the earpiece
amplifier.
The DC line current flowing into the set is determined by
the exchange supply voltage (V
resistance (R
(R
below 8 mA, the internal reference voltage (generating
V
that more sets can operate in parallel with DC line voltages
(excluding the polarity guard) down to an absolute
minimum voltage of 1.6 V. At currents below 8 mA, the
circuit has limited sending and receiving levels. This is
called the low voltage area.
1997 Mar 27
V
V
handbook, halfpage
ref
CC
CCO
line
Low voltage versatile telephone
transmission circuit with dialler interface
) is automatically adjusted to a lower value. This means
) and the reference voltage (V
CC
=
=
. This voltage supply is derived from the line
V
Fig.5 V
V CCO
V
CCO
R CCint
LN
exch
–
–
CC
R
R
CC
), the DC resistance of the telephone line
CC
voltage depends on the current
CCint
V CC
voltage supply for peripherals.
V EE
I
I rec
CC
I
p
VCC
–
I
rec
. It may also be used to
exch
PERIPHERAL
CC
CIRCUIT
ref
), the feeding bridge
) and must be
). With line currents
CCint
is the internal
rec
MBE792
I P
is the
6
Set impedance
In the audio frequency range, the dynamic impedance is
mainly determined by the R
impedance of the circuits is illustrated in Fig.7.
LED supply (pin I
The TEA1113 gives an on-hook/off-hook status indication.
This is achieved by a current made available to drive an
LED connected between pins I
voltage area, which corresponds to low line current
conditions, no current is available for this LED. For line
currents higher than a threshold current, the I
increases proportionally to the line current (with a ratio of
one third).The I
(see Fig.8).
For 17 mA < I
This LED driver is referenced to SLPE. Consequently, all
the I
The AGC characteristics are not disturbed (see Fig.3 for
the supply configuration).
Microphone amplifier (pins MIC , MIC and GAS)
The TEA1113 has symmetrical microphone inputs.
The input impedance between pins MIC and MIC is
64 k (2
to pin LN is set to 51.8 dB (typ). The gain can be
decreased by connecting an external resistor R
between pins GAS and REG. The adjustment range is
13 dB. A capacitor C
and REG can be used to provide a first-order low-pass
filter. The cut-off frequency corresponds to the time
constant C
resistor which sets the gain with a typical value of 69 k .
Automatic gain control is provided on this amplifier for line
loss compensation.
Dynamic limiter and microphone mute
(pin DLS/MMUTE)
The dynamic limiter only acts on the microphone channel,
this is to prevent clipping of the line signal. To prevent
distortion, the microphone gain is rapidly reduced when
peaks on the line signal exceed an internally determined
threshold level or when the current in the transmit output
stage is insufficient. The time in which the gain reduction
is realized is very short (attack time). The microphone
channel stays in the reduced gain condition until the peaks
I
LED
LED
=
I
--------------------- -
supply current will flow through the R
line
GAS
32 k ). The voltage gain from pins MIC /MIC
3
–
line
17
LED
(R
< 77 mA:
LED
current is internally limited to 19.5 mA
GASint
GAS
)
connected between pins GAS
// R
CC
GAS
resistor. The equivalent
LED
). R
and LN. In the low
GASint
Product specification
TEA1113
is the internal
SLPE
LED
GAS
current
resistor.