technical data 1 low voltage transmission circuit with dialler interface the ila1062a is an integrated circuit that perform all speech and line interface functions required in fully electronic telephone sets. they perform electronic switching between dialling and speech. the ics operate at line voltage down to 1.6 v dc (with reduced performance) to facilitate the use of more telephone sets connected in parallel. ? low dc line voltage: operates down to 1.6 v (excluding polarity guard) ? voltage regulator with adjustable static resistance ? provides a supply for external circuits ? symmertical high-impedance inputs (64 k ? ) for dynamic, magnetic or piezo-electric microphones ? asymmetrical high-impedance input (32 k ? ) for electret microphones ? dtmf signal input with confidence tone ? mute input for pulse or dtmf dialing: active low (mute) ? receiving amplifier for dynamic, magnetic or piezo-electric earpieces ? large gain setting ranges on microphone and earpiece amplifiers ? line loss compensation (line current dependent) for microphone and earpiece amplifiers ? gain control curve adaptable to exchange supply ? dc line voltage adjustment facility ila1062a ordering information ILA1062AN plastic t a = -25 to 75 c for package pin assignment block diagram
ila1062a 2 pin description pin no designation description 1 ln positive line terminal 2 gas1 gain adjustment; transmitting amplifier 3 gas2 gain adjustment; transmitting amplifier 4 qr non-inverting output; receiving amplifier 5 gar gain adjustment; receiving amplifier 6 mic- inverting microphone input 7 mic+ non-inverting microphone input 8 stab current stabilizer 9v ee negative line terminal 10 ir receiving amplifier input 11 dtmf dual-tone multi-frequency input 12 mute mute input 13 v cc possitive supply decoupling 14 reg voltage regulator decoupling 15 agc automatic gain control input 16 slpe slope (dc resistance) adjustment 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 derived 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. dialling 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 an internal current stabilizer operating at a level determined by a 3.6 k ? resistor connected between stab and v ee (see fig.1). figure 1. supply arrengement when the line current (i line ) is more than 0.5 ma greater than the sum of the ic supply current (i cc ) and the current draw 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 -3 a)-i p ) x r9
ila1062a 3 v ref is an internally generated temperature compensated reference voltage of 3.7 v 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). under normal conditions, when i slpe >>i cc + 0.5 ma + i p , the static behaviour of the circuit is that of a 3.7 v 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.2 shows the equivalent impedance of the circuit. l eq = c3 x r9 x r p r p = 16.2 k ? figure 2. equivalent impedance circuit at line currents below 9 ma the internal reference voltage is automatically adjusted to a lower value (typically 1.6 v at 1 ma) this means that more sets can be operated in parallel with dc line voltages (excluding the polarity guard) down to an absolute minimum voltage of 1.6 v. at line currents below 9 ma 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 32 k ? ) and its voltage gain is typically 52 db (when r7 = 68 k ? , see figure 3). 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 v ee . the value of c6 is 100 pf but this may be increased to obtain a first- order low-pass filter. the value of c8 is 10 limes the value of c6. the cut-off frequency corresponds to the time constant r7 x c6. input mute when mute is low or open circuit, the dtmf input is enabled and the microphone and receiving amplifier inputs are inhibited. the reverse is true when mute is high, mute switching causes only negligible clicking on the line and earpiece output. if the number of parallel sets in use causes a drop in line current to below 6 ma the dtmf amplifier becomes active independent to the dc level applied to the mute input. dial-tone multi-frequency input dtmf when the dtmf input is enabled dialling tones may be sent on to the line. the voltage gain from dtmf to ln is typically 25.5 db (when r7 = 68 k ? ) 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). the ir to qr gain is typically 31 db (when r4 = 100 k ? ). it can be adjusted between 20 and 31 db 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 (32 db) from the amplifier gain. two external capacitors, c4 and c7, ensure stability. c4 is normally 100 pf 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.
ila1062a 4 automatic gain control input agc automatic line loss compensation is achieved by connecting a resistor (r6) between agc and v ee . 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 0.5 mm diameter twisted-pair copper cable with a dc resistance of 176 ? /km and average attenuation of 1.2 db/km. resistor r6 should be chosen in accordance with the exchange supply voltage and its feeding bridge resistance (see table 1). table 1 values of resistor r6 for optimum line-loss compensation at various values of exchange supply voltage (v exch ) and exchange feeding bridge resistance (r exch ); r9 = 20 ? . v exch (v) 400 r exch ( ? ) 600 r exch ( ? ) 800 r exch ( ? ) 1000 r exch ( ? ) r6(k ? ) 36 100 78.7 - - 48 140 110 93.1 82 60 - - 120 102 the ratio of start and stop currents of the ags curve is independent of the value of r6. if no automatic line-loss compensation is required the ags pin may be left open-circuit. the amplifiers, in this condition, will give their maximum specified gain. sidetone suppression the anti-sidetone network, r1//z line , r2, r3, r8, r9 and z bal (see fig4) suppresses the transmitted signal in the earpiece. maximum compensation is obtained when the following conditions are fulfilled: r9 x r2 = r1 x ( r3 + ) (1) = (2) it fixed values are chosen for r1, r2, r3 and r9, then condition (1) will always be fulfilled when ? r8//z bal ? <>r9 to avoid influencing the transmit gain. in practise z line varies considerably with the line type and length. the value chosen for z bal should therefore be for an average line length thus giving optimum setting for short or long lines. maximum ratings * symbol parameter condition min max unit v ln positive continuous line voltage - 12 v v ln(r) repetitive line voltage during switch-on or line interruption - 13.2 v v ln(rm) repetitive peak line voltage for a 1 ms pulse per 5 s r9 = 20 ? ; r10 = 13 ? ; see fig.5 -28 v i line line current r9 = 20 ? - 140 ma v in positive input voltage - v cc +0.7 v negative input voltage - -0.7 v p d total power dissipation r9 = 20 ? ; note 1 - 666 mw tstg storage temperature -40 +125 c * maximum ratings are those values beyond which damage to the device may occur. functional operation should be restricted to the recommended operating conditions. note 1. calculated for the maximum operating temperature specified (t amb = 75 c) and a maximum junction temperature of 125 c. r8 x z bal r8 +z bal r8 r1 z bal z bal + r8 r8 r1 z line z line + r1 input voltage on all other pins
ila1062a 5 recommended operating conditions symbol parameter conditions min typ max unit i line operating line current normal operation with reduced performance 11 1 - - 140 11 ma ma v cc supply voltage for peripherals i line = 15 ma i p = 1.2 ma; mute = low i p = 0 ma; mute = low 2.2 - - 3.4 - - v v g v voltage gain microphone amplifier receiving amplifier 44 20 - - 52 31 db db t amb operating ambient temperature -25 - +75 c line loss compensation ? g v gain control - 5.8 - db v exch exchange supply voltage 36 - 60 v r exch exchange feeding bridge resistance 0.4 - 1 k ? this device contains protection circuitry to guard against damage due to high static voltages or electric fields. however, precautions must be taken to avoid applications of any voltage higher than maximum rated voltages to this high-impedance circuit. for proper operation, v in and v out should be constrained to the range gnd (v in or v out ) v cc . unused inputs must always be tied to an appropriate logic voltage level (e.g., either gnd or v cc ). unused outputs must be left open. electrical characteristics (i line = 11 to 140 ma; v ee = 0 v; f = 800 hz;t amb = 25 c; unless other specified) symbol parameter test conditions guaranteed limits unit min typ max supplies ln and v cc (pins 1 and 13) v ln voltage drop over circuit between ln and v ee mic inputs open-circuit i line = 1 ma i line = 4 ma i line = 15 ma i line = 100 ma i line = 140 ma - - 3.56 4.9 - 1.6 1.9 - - - - - 4.25 6.5 7.5 v ? v ln / ? t variation with temperature i line = 15 ma - -0.3 - mv/k v ln voltage drop over circuit between ln and v ee with external resistor r va i line = 15 ma r va (ln to reg)=68k ? r va (ln to slpe)=39k ? 3.5 4.5 v i cc supply current v cc = 2.8 v 1.35 ma (continued)
ila1062a 6 electrical characteristics (i line = 11 to 140 ma; v ee = 0 v; f = 800 hz;t amb = 25 c; unless other specified) symbol parameter test conditions guaranteed limits unit min typ max microphone inputs mic- and mic+ (pins 6 and 7) ? z i ? input impedance differential single-ended between mic- and mic+ mic- or mic+ to v ee - - 64 32 - - k ? cmrr common mode rejection ratio -82-db g v voltage gain mic+ or mic- to ln i line = 15 ma r7 = 68 k ? 50.5 53.5 db ? g vf gain variation with frequency reference to 800 hz f = 300 and 3400 hz - 0.2 -db ? g vt gain variation with temperature referenced to 25 c without r6; i line =50 ma; t amb = -25 and +75 c - 0.2 -db dtmf input (pin 11) ? z i ? input impedance - 20.7 - k ? g v voltage gain from dtmf to ln i line 15 ma; r7 = 68 k ? 24.0 - 27.0 db ? g vf gain variation with frequency reference to 800 hz f = 300 and 3400 hz - 0.2 -db ? g vt gain variation with temperature referenced to 25 c i line =50 ma; t amb = -25 and +75 c - 0.2 -db gain adjustment inputs gas1 and gas2 (pins 2 and 3) ? g v transmitting amplifier gain variation by adjustment of r7 between gas1 and gas2 -8 - 0 db sending amplifier output ln (pin 1) v ln(rms) output voltage (rms value) thd = 10% i line = 4 ma i line = 15 ma - 1.7 0.8 - - - v v no(rms) noise output voltage (rms value) i line = 15 ma; r7 =68k ? 200 ? between mic- and mic+ --69-dbmp receiving amplifier input ir (pin 10) ? z i ? input impedance - 21 - k ? receiving amplifier output qr (pin 4) ? z o ? output impedance - 4 - ? g v voltage gain from ir to qr i line 15 ma; r l = 300 ? (from pin 9 to pin 4) 29.5 - 32.5 db (continued)
ila1062a 7 electrical characteristics (i line = 11 to 140 ma; v ee = 0 v; f = 800 hz;t amb = 25 c; unless other specified) symbol parameter test conditions guaranteed limits unit min typ max ? g vf gain variation with frequency reference to 800 hz f = 300 and 3400 hz - 0.2 -db ? g vt gain variation with temperature referenced to 25 c without r6; i line =50 ma; t amb = -25 and +75 c - 0.2 -db v o(rms) output voltage (rms value) thd = 2%; sine wave drive: r4 = 100 k ? ; i line = 15 ma; i p = 0 ma r l = 150 ? r l = 450 ? 0.22 0.3 - - - - v v o(rms) output voltage (rms value) thd=10%; r4=100 k ? ; i line = 4 ma; r l = 150 ? -15-mv v no(rms) noise output voltage (rms value) i line = 15 ma; r4=100k ? ir open-circuit psophometrically weighted; r l =300 ? -50- v gain adjustment input gar (pin 5) ? g v receiving amplifier gain variation by adjustment of r4 between gar and or -11 - 0 db mute input (pin 12) v ih high level input voltage 1.5 - v cc v v il low level input voltage - - 0.3 v i mute input current - - 15 a raduction of gain ? g v mic+ or mic- to ln mute = low - 70 - db g v voltage gain from dtmf to qr r4 = 100 k ? r l = 300 ? --17-db automatic gain control input agc (pin 15) ? g v controlling the gain from ir to qr and the gain from mic+, mic- to ln gain control range r6 = 110 k ? (between agc and v ee ) i line = 70 ma - -5.8 - db i lineh highest line current for maximum gain -23-ma i linel lowest line current for minimum gain -61-ma
ila1062a 8 voltage gain is defined as g v = 20 log for measuring gain from mic+ and mic- the mute input should be high. for measuring the dtmf input, the mute input should be low or open-circuit. inputs not being tested should be open-circuit. figure 3. test circuit for defining ila1062a voltage gain of mic+, mic- and dtmf inputs. figure 4. equivalent circuit of ila1062a anti-sidetone bridge v o v i
ila1062a 9 the diode bridge, the zener diode and r10 limit the current into, and the voltage across, the circuit during line transients. a different protaction arrangement is required for pulse dialling or register recall. the dc line voltage can be set to a higher value by the resistor r va (reg to slpe). figure 5. typical application of ila1062a, with piezo-electric earpiece and dtmf dialling.
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