ILA1062A データシートの表示（PDF） - IK Semicon Co., Ltd
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ILA1062A Datasheet PDF : 11 Pages
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Dual-tone multi-frequency input DTMF
When the DTMF input is enable dialing tones may be
sent on to the line. The voltage gain from DTMF to LN
is typically 25.5 dB (when R7=68kΩ) and varies with
R7 in the same way as the microphone gain. The
signaling 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). 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 x
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
Automatic line loss compensation is achieved by
connecting a resistor (R6) between AGC and VEE.
The automatic gain control varies the gain of the
microphone amplifier and the receiving amplifier in
accordance with the DC line current. The control range
is 5.8 dB which corresponds to a line length of 5 km for
a 0.5mm diameter twisted-pair copper cable with a DC
resistance of 176 dB/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. The ratio of start and stop currents of the
AGC curve is independent of the value of R6. If no
ILA1062/1062A
automatic line-loss compensation is required the AGC
pin may be left open-circuit. The amplifiers, in this
condition, will give their maximum specified gain.
Sidetone suppression
The anti-sidetone network, R1//Zline, R2, R3, R8, R9
and Zbal suppresses the transmitted signal in the
earpiece. Maximum compensation is obtained when the
following conditions are fulfilled:
R 8 x Zbal
R9 x R2 = R1 x R 3 + R 8 + Zbal
(1)
Zbal
Zline
=
(2)
Zbal + R 8 Zline+ R 1
If fixed values are chosen for R1, R2, R3 and R9, then
condition (1) will always be fulfilled when
To obtain optimum sidetone suppression, condition (2)
has to be fulfilled which results in:
R8
Zbal =
x Zline = k x Zline
R1
R8
Where k is scale factor; k =
R1
The scale factor k, dependent on the value of R8, is
chosen to meet the following criteria:
- compatibility with a standard capacitor from the E6 or
E12 range for Zbal
- |Zbal//R8|<<R8 fulfilling condition (a) and thus
ensuring correct
anti-sidetone bridge operation
- |Zbal + R8|>>R9 to avoid influencing the transmit gain.
In practise Zline varies considerably with the line type
and length. The value chosen for Zbal should therefore
be for an average line thus giving optimum setting for
short or long lines.
2011, March, ver.01
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