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UTCTEA1062 Datasheet(PDF) 6 Page - Unisonic Technologies

Part No. UTCTEA1062
Description  LOW VOLTAGE TELEPHONE TRANSMISSION CIRCUIT WITH DIALLER INTERFACE
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Maker  UTC [Unisonic Technologies]
Homepage  http://www.utc-ic.com
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UTCTEA1062 Datasheet(HTML) 6 Page - Unisonic Technologies

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UTCTEA1062/1062A
LINEARINTEGRATEDCIRCUIT
UTC UNISONIC TECHNOLOGIES CO., LTD.
6
QW-R108-001,A
FUNCTIONAL DESCRIPTION
Supply: VCC, LN, SLPE, REG and STAB
Power
for
the
UTC
TEA1062/1062A
and
its
peripheral
circuits
is
usually
obtained
from
the
telephone line. The IC supply
voltage is derived from
the line via a dropping resistor and regulated by the
UTC TEA1062/1062A,The supply voltage
Vcc may
also be used to supply external circuits e.g. dialling and
control circuits. Decoupling of the supply voltage is
performed by a capacitor between Vcc
and VEE
while the internal voltage regulator is decoupled by a
capacitor between REG and VEE. The DC current
drawn by the device will vary in accordance with
varying values of the exchange voltage(Vexch), the
feeding bridge resistance(Rexch) and the DC resistance
of
the telephone line(Rline). The UTC TEA1062/1062A
has an internal current stabilizer operating at a level
determined by a 3.6k¦ ¸resistor connected between
STAB and VEE(
see Fig.8). When the line current(Iline)
is more than 0.5 mA greater than the sum of the IC
supply current ( Icc) and the current drawn by the
peripheral circuitry connected to VCC(lp) the excess
current is shunted to VEE via LN. The regulated voltage
on the line terminal(VLN) can be calculated as:
VLN=Vref+ISLPE*R9 or;
VLN=Vref+[(Iline – ICC - 0.5*10-
3
A)£ -
Ip]*R9
where:Vref is an internally generated temperature
compensated reference voltage of 3.7V and R9 is an
external resistor connected between SLPE and VEE. In
normal use the value of R9 would be 20
Ω. Changing
the value of R9 will also affect microphone gain, DTMF
gain,gain
control
characteristics,
side
tone
level,
maxmimum
output
swing
on
LN
and
the
DC
characteristics (especially at the lower voltages). Under
normal
conditions, when ISLPE>=ICC+0.5mA +Ip, the
static behaviour of the circuit is that of a 3.7V regulator
diode with an internal resistance equal
to that of R9.In
the audio frequency range the dynamic impedance is
largely determined by R1.Fig.3 shows the equivalent
impedance of the circuit.
Microphone inputs(MIC+ and MIC-) and
gain pins (GAS1 and GAS2)
The UTC TEA1062/1062A has symmetrical inputs.
Its input impedance is 64k
Ω (2*32kΩ) and its voltage
gain is typically 52 dB (when R7=68k
Ω.see Fig.13).
Dynamic, magnetic, piezoelectric or electret (with built-
in FET source followers) can be used. Microphone
arrangements are illustrated in Fig.10. The gain of the
microphone amplifier can be adjusted between 44dB
and 52dB to suit the sensitivity of the transducer in use.
The gain is proportional to the value of R7 which is
connected between GAS1 and GAS2. Stability is
ensured by the external capacitors, C6 connected
between GAS1 and SLPE and C8 connected between
GAS1 and VEE. The value of
C6 is 100pF but this
may be increased to obtain a first-order low-pass filter.
The value of C8 is 10 times the value of C6. The cut-off
frequency corresponds to the time constant R7*C6.
Mute input (MUTE)
A LOW(UTC TEA1062 is HIGH) level at MUTE
enables DTMF input
and inhibites the microphone
inputs and the receiving amplifier inputs; a HIGH(UTC
TEA1062 is LOW) level or an open circuit does the
reverse. Switching the mute input will cause negligible
clickis at the telephone outputs and on the line. In case
the line current drops below 6mA(parallal opration of
more sets) the circuit is always in speech condition
independant of the DC level applied to the MUTE input.
Dual-tone multi-frequency input (DTMF)
When the DTMF input is enabled dialling tones may
be sent onto the line. The voltage gain from DTMF to
LN is typically 25.5dB(when R7=68k
Ω) and varies with
R7 in the same way as the microphone gain. The
signalling tones can be heard in the earpiece at a low
level(confidence tone).
Receiving amplifier (IR,QR and GAR)
The receiving
amplifier has one input (IR) and a
non-inverting output (QR). Earpiece arrangements are
illustrated in Fig.11. The IR to QR gain is typically 31dB
(when R4=100k
Ω). It can be adjusted between 20 and
31dB to match the sensitivity of the transducer in use.
The gain is set with the value of R4 which is connected
between GAR and QR.The overall receive gain,
between LN and QR, is calculated by substracting the
anti-sidetone network attenuation (32dB) from the
amplifier gain.
Two external capacitors, C4 and C7,
ensure stability. C4 is normally 100pF and C7 is 10
times the value of C4. The value of C4 may be
increased to obtain a first-order low-pass filter.The cut-
off frequency will depend on the time constant R4*C4.
The output voltage of the receiving amplifier is specified
for
continuous-wave drive. The maximum output
voltage will be higher under speech conditions where
the peak to RMS ratio is higher.


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