TEA1062AN-D16-T UTC [Unisonic Technologies], TEA1062AN-D16-T Datasheet - Page 8

• Manufacturer Part Number: TEA1062AN-D16-T
• Description: LOW VOLTAGE TELEPHONE TRANSMISSION CIRCUIT WITH DIALLER INTERFACE
• Manufacturer: UTC [Unisonic Technologies]

TEA1062N/TEA1062AN
RECEIVING AMPLIFIER (IR,QR AND GAR)
in Fig.11. The IR to QR gain is typically 31dB (when R4=100kΩ). 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 subtracting 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.
AUTOMATIC GAIN CONTROL INPUT (AGC)
gain control varies the gain of the microphone amplifier and the receiving amplifier in accordance with the DC line
current. The control range is 5.8dB which corresponds to a line length of 5km for a 0.5mm diameter twisted pair
copper cable with a DC resistance of 176Ω/km and average attenuation of 1.2dB/km. Resistor R6 should be chosen
in accordance with the exchange supply voltage and its feeding bridge resistance(see Fig.12 and Table 1). The ratio
of start and stop currents of the AGC curve is independent of the value of R6. If no automatic line loss compensation
is required the AGC may be left open-circuit. The amplifier, in this condition, will give their maximum specified gain.
SIDE-TONE SUPPRESSION
earpiece. Compensation is maximum when the following conditions are fulfilled:
If fixed values are chosen for R1, R2, R3 and R9 then condition(a) will always be fulfilled when ︱R8//Z
To obtain optimum side-tone suppression condition(b) has to be fulfilled which results in:
(a) Compatibility with a standard capacitor from the
(b) ︱Z
(c) ︱Z
In practice Z
average line length thus giving optimum setting for short or long lines.
EXAMPLE:
210Ω+(1265Ω//140nF) representing a 5km line of 0.5 mm diameter, copper, twisted pair cable matched to
600Ω(176Ω/km;38nF/km). When k=0.64 then R8=390Ω, Z
The receiving amplifier has one input (IR) and a non-inverting output (QR). Earpiece arrangements are illustrated
Automatic line loss compensation is achieved by connecting a resistor(R6) between AGC and V
The anti-sidetone network, R1//Z
Z
K=(R8/R1).
The scale factor (k), dependent on the value of R8, is chosen to meet following criteria:
The balance impedance Z
E6 or E12 range for Z
BAL
FUNCTIONAL DESCRIPTION(Cont.)
=(R8/R1) Z
BAL
BAL
+R8︱>>R9 to avoid influencing the trans-mitter gain.
//R8︱<<R3 fulfilling condition (a) and thus ensuring correct anti-sidetone bridge operation,
UNISONIC TECHNOLOGIES CO., LTD
LINE
www.unisonic.com.tw
varies considerably with the type and length. The value chosen for Z
LINE
=k*Z
BAL
LINE
,
BAL
where k is a scale factor;
at which the optimum suppression is present can be calculated by: Suppose ZI
LINE
, R2, R3, R8, R9 and Z
BAL
=130Ω+(820Ω//220nF).
BAL
, (see Fig.4) suppresses the transmitted signal in the
LINEAR INTEGRATED CIRCUIT
BAL
should therefore be for an
EE
. The automatic
QW-R108-011.C
BAL
︱<<R3.
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LINE
=