tea1083at NXP Semiconductors, tea1083at Datasheet - Page 6

• Manufacturer Part Number: tea1083at
• Description: Call Progress Monitor For Line Powered Telephone Sets
• Manufacturer: NXP Semiconductors

Philips Semiconductors
The circuit stabilizes its own supply voltage at V
Transistor TR1 provides the supplies for the internal
circuits. Transistor TR2 is used to minimize signal
distortion on the line by momentarily diverting the input
current to V
voltage at V
fixed to a typical value of 2.95 V.
The supply at V
220 F capacitor (C20).
The DC voltage (V
transmission IC and V
V
The reference voltage of the transmission IC has to be
adjusted to a level where V
400 mV. The minimum voltage space between SUP and
V
the internal supply for mean speech levels. V
specified maximum level.
The internal current consumption of the TEA1083/83A
(I
The current I
0.4 mA) for the circuitry connected to SUP and I
(approximately 2.1 mA) for the internal circuitry connected
to V
LOUDSPEAKER AMPLIFIER (LSI1/LSI2 and QLS)
The TEA1083/83A has symmetrical inputs at LSI1 and
LSI2. The input signal is normally taken from the earpiece
output of the transmission circuit (see Fig.5) and/or from
the signal output of the DTMF generator via a resistive
attenuator.
The attenuation factor must be chosen in accordance with
the output levels from the transmission IC and/or DTMF
generator and, in accordance with the required output
power and permitted signal distortion from the
loudspeaker signal.
The output QLS drives the loudspeaker as a single-ended
load. The output stage has been optimized for use with a
50
loudspeaker amplifier is enabled when the LSE input goes
HIGH. The gain of the amplifier is fixed at 35 dB.
Volume control of the loudspeaker signal can be obtained
by using a level control at the input (see Fig.5).
March 1994
SUP0
SUP
BB
Call progress monitor for line powered
telephone sets
BB
(400 mV) is required to maintain a 'high' efficiency of
loudspeaker (e.g. Philips type AD2071). The
) is typically 2.5 mA (where V
(see Fig.6).
V
SS
SUP
SS
= V
SUP0
whenever the instantaneous value of the
LN SLPE
drops below the supply voltage V
BB
consists of currents I
is decoupled with respect to V
SUP
int
; thus
V
V
SS
int
SUP
) is determined by the
.
V
SUP
BB (max)
BIAS
V
(approximately
is greater than
SS
BB (max)
= 3.6 V).
BB
BB0
BB
SS
.
. V
by a
is the
BB
is
6
The maximum voltage swing at the QLS output is
V
V
I
available voltage space (V
lower supply currents will result in an increase of the
harmonic distortion due to signal clipping.
With a limit of 2.5 V (p-p), the maximum output swing is
dependent on the supply current and loudspeaker
impedance. It can be approximated, for low distortions, by
the following equation:
V
Where;
POWER-DOWN INPUT (PD)
During pulse dialling or register recall (timed loop break)
the telephone line is interrupted, thereby breaking the
supply current to the transmission IC. The capacitor
connected to V
TEA1083/83A during the supply breaks.
By making the PD input HIGH during the loop break, the
requirement on the capacitor is eased and, consequently,
the internal current consumption I
reduced from 2.1 mA to 400 A typically. Transistors TR1
and TR2 are inhibited during power-down and the bias
current is reduced from approximately 400 A to
approximately 50 A with V
equation:
I
Where 3.6
2V
(approximately 1.3 V)
Ra is an internal resistor (typical 50 k )
LOUDSPEAKER ENABLE INPUT (LSE)
The LSE input has a pull-down structure. It switches the
loudspeaker amplifier, in the monitoring condition, by
applying a HIGH level at the input. The amplifier is in the
standby condition when LSE is LOW (input open-circuit or
connected to V
SUP
SUP(PD)
O(p-p)
LSI
O(p-p)
V
R
I
d
SUPO
O(p-p)
LS
is the voltage drop across 2 internal diodes
is approximately 16 mV(rms) and the supply current
= the loudspeaker impedance
= 2.5 V (typical with 50
= 2
11 mA. In this condition the signal is limited by the
= I
= 2.5 mA (typ.)
= the peak-to-peak level of the loudspeaker
BIAS(PD)
V
(I
BB
SUP
SS
SUP
).
provides the supply for the
= (V
I
V
SUPO
TEA1083; TEA1083A
SUP
BB
BB
)
SUP
). Higher input levels and/or
2V
3 V
= 3.6 V in the following
d
)/Ra
BB0
load). The input level
R
Product specification
(see Fig.5) is
LS