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TEA1113 Datasheet(PDF) 6 Page - NXP Semiconductors

Part No. TEA1113
Description  Low voltage versatile telephone transmission circuit with dialler interface
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Maker  PHILIPS [NXP Semiconductors]
Homepage  http://www.nxp.com
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TEA1113 Datasheet(HTML) 6 Page - NXP Semiconductors

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1997 Mar 27
6
Philips Semiconductors
Product specification
Low voltage versatile telephone
transmission circuit with dialler interface
TEA1113
The internal circuitry of the TEA1113 is supplied from
pin VCC. This voltage supply is derived from the line
voltage by means of a resistor (RCC) and must be
decoupled by a capacitor CVCC. It may also be used to
supply peripheral circuits such as dialling or control
circuits. The VCC voltage depends on the current
consumed by the IC and the peripheral circuits as shown
by the formula (see also Figs 5 and 6). RCCint is the internal
impedance of the voltage supply point, and Irec is the
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 (Vexch), the feeding bridge
resistance (Rexch), the DC resistance of the telephone line
(Rline) and the reference voltage (Vref). With line currents
below 8 mA, the internal reference voltage (generating
Vref) is automatically adjusted to a lower value. This means
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.
V
CC
V
CCO
R
CCint
I
p
I
rec
()
×
=
V
CCO
V
LN
R
CC
I
CC
×
=
handbook, halfpage
PERIPHERAL
CIRCUIT
IP
Irec
RCCint
VCC
VEE
VCCO
MBE792
Fig.5 VCC voltage supply for peripherals.
Set impedance
In the audio frequency range, the dynamic impedance is
mainly determined by the RCC resistor. The equivalent
impedance of the circuits is illustrated in Fig.7.
LED supply (pin ILED)
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 ILED and LN. In the low
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 ILED current
increases proportionally to the line current (with a ratio of
one third).The ILED current is internally limited to 19.5 mA
(see Fig.8).
For 17 mA < Iline < 77 mA:
This LED driver is referenced to SLPE. Consequently, all
the ILED supply current will flow through the RSLPE resistor.
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
Ω (2 × 32 kΩ). The voltage gain from pins MIC+/MIC−
to pin LN is set to 51.8 dB (typ). The gain can be
decreased by connecting an external resistor RGAS
between pins GAS and REG. The adjustment range is
13 dB. A capacitor CGAS connected between pins GAS
and REG can be used to provide a first-order low-pass
filter. The cut-off frequency corresponds to the time
constant CGAS × (RGASint // RGAS). RGASint is the internal
resistor which sets the gain with a typical value of 69 k
Ω.
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
I
line
17
3
----------------------
=


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