ILA1062 Datasheet, PDF (3/9 Pages) Integral Corp. – TELEPHONE SPEECH NETWORK WITH DIALER INTERFACE

ILA1062/ILA1062A
FUNCTIONAL DESCRIPTION
Supplies V_CC, LN, SLPE, REG and STAB
Power for the IC and its peripheral circuits is usually obtained from the telephone line. The supply voltage is
delivered from the line via a dropping resistor and regulated by the IC. The supply voltage V_CC may also be
used to supply external circuits e.g. dialing and control circuits.
Decoupling of the supply voltage is performed by a capacitor between V_CC and V_EE . The internal voltage
regulator is decoupled by a capacitor between REG and V_EE.
The DC current flowing into the set is determined by the exchange supply voltage V_exch , the feeding bridge
resistance R_exch and the DC resistance of the telephone
line R_line .
The circuit has internal current stabilizer operating at a level determined by a 3.6 k? resistor connected
between STAB and V_EE (see Fig.6). When the line current (I_line) is more than 0.5mA greater than the sum of
the IC supply current (I_CC) and the current drawn by the peripheral circuitry connected to V_CC (I_p) the excess
current is shunted to V_EE via LN.
The regulated voltage on the line terminal (V_LN) can be calculated as:
V_LN = V_ref + I_SLPE x R9
V_LN = V_ref + {(I_line - I_CC - 0.5 x 10^-3A) - I_p} x R9
V_ref is an internally generated temperature compensated reference voltage of 3.7V and R9 is an external
resistor connected between SLPE and V_EE.
In normal use the value of R9 would be 20?.
Changing the value of R9 will also affect microphone gain, DTMF gain, gain control characteristics, sidetone
level, maximum output swing on LN and the DC characteristics (especially at the lower voltages).
Fig.2 Equivalent impedance circuit
LN
Under normal conditions, when I_SLPE >>I_CC + 0.5mA + I_p, the static
behaviour of the circuit is that of a 3.7V regulator diode with an
Leq
Rp
R1
internal resistance equal to that of R9. In the audio frequency
range the dynamic impedance is largely determined by R1. Fig.2
Vref
REG
show the equivalent impedance of the circuit.
VCC
At line currents below 9mA the internal reference voltage is
R9
automatically adjusted to a lower value (typically 1.6V at 1mA).
20Ω
C3
C1
This means that more sets can be operated in parallel with DC
4.7µF
100µF line voltage (excluding the polarity guard) down to an absolute
VEE
Leq = C3 x R9 x Rp
Rp = 16.2 kΩ
minimum voltage of 1.6V. At line currents below 9mA the circuit
has limited sending and receiving levels. The internal reference
voltage can be adjusted by means of an external resistor (R_VA).
This resistor when connected between LN and REG will decrease
the internal reference voltage and when connected between REG
and SLPE will increase the internal reference voltage.
Microphone inputs MIC+ and MIC- and gain pins GAS1 and GAS2
The circuit has symmetrical microphone inputs. Its input impedance is 64 k? (2 x 32k?) and its voltage gain is
typically 52 dB (when R7 = 68k?; see Fig.6).
Dynamic, magnetic, piezo-electric or electret (with built-in FET source followers) can be used.
The gain of the microphone amplifier can be adjusted between 44 dB and 52 dB 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 two 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
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