tea1110auh NXP Semiconductors, tea1110auh Datasheet - Page 6

• Manufacturer Part Number: tea1110auh
• Description: Low Voltage Versatile Telephone Transmission Circuit With Dialler Interface
• Manufacturer: NXP Semiconductors

Philips Semiconductors
The internal circuitry of the TEA1110A 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:
R
supply, and I
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 7.5 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 7.5 mA, the
circuit has limited sending and receiving levels. This is
called the low voltage area.
2000 Feb 15
V
handbook, halfpage
ref
CCint
CC0
line
Low voltage versatile telephone
transmission circuit with dialler interface
(1) Influence of R
(2) V
) is automatically adjusted to a lower value. This means
V ref
) and the reference voltage (V
CC
(V)
is the internal equivalent resistance of the voltage
Fig.4 Reference voltage adjustment by R
=
6.0
5.0
4.0
3.0
. This voltage supply is derived from the line
ref
10
V
without influence of R
4
LN
rec
exch
–
CC
R
is the current consumed by the output
V
), the DC resistance of the telephone line
CC
VA
voltage depends on the current
CC
on V
10
=
I
CC
ref
5
(1)
(2)
V
.
CC0
VA
(see also Figs 5 and 6).
VCC
.
–
. It may also be used to
R
exch
CC
CCint
10
ref
), the feeding bridge
) and must be
6
). With line currents
R VA ( )
I
P
–
MGD176
I
rec
10
VA
7
.
6
Set impedance
In the audio frequency range, the dynamic impedance is
mainly determined by the R
impedance of the circuit is illustrated in Fig.7.
Microphone amplifier (pins MIC+ and MIC )
The TEA1110A has symmetrical microphone inputs. The
input impedance between pins MIC+ and MIC is 64 k
(2
LN is set at 43.7 dB (typ).
Automatic gain control is provided on this amplifier for line
loss compensation.
Receiving amplifier (pins IR, GAR and QR)
The receiving amplifier has one input (IR) and one output
(QR). The input impedance between pin IR and pin V
20 k . The voltage gain from pin IR to pin QR is set at
33 dB (typ). The gain can be decreased by connecting an
external resistor R
adjustment range is 14 dB. Two external capacitors C
(connected between GAR and QR) and C
between GAR and V
capacitor provides a first-order low-pass filter. The cut-off
frequency corresponds to the time constant
C
which sets the gain with a typical value of 125 k . The
condition C
stability.
The output voltage of the receiving amplifier is specified for
continuous wave drive. The maximum output swing
depends on the DC line voltage, the R
current consumption of the circuit, the I
consumption of the peripheral circuits and the load
impedance.
Automatic gain control is provided on this amplifier for line
loss compensation.
Automatic gain control (pin AGC)
The TEA1110A performs automatic line loss
compensation. The automatic gain control varies the gain
of the microphone amplifier and the gain of the receiving
amplifier in accordance with the DC line current. The
control range is 5.9 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
GAR
32 k ). The voltage gain from pins MIC+/MIC to pin
(R
AGC
GARint
GARS
between pins AGC and V
// R
= 10
GAR
GAR
EE
between pins GAR and QR; the
) ensure stability. The C
). R
C
GAR
GARint
CC
must be fulfilled to ensure
resistor. The equivalent
is the internal resistor
Product specification
CC
TEA1110A
P
EE
current
GARS
resistor, the I
.
(connected
GAR
EE
GAR
CC
is