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s ilicore shaoxing silicore technology co.,ltd www. silicore. com. cn chmc 1/15 low voltage transm ission circuits with dialler interface SC1062/SC1062a general description outline drawing the SC1062/SC1062a are integrated circuits that perform all speech and line interface functions required in fully electronic telephone sets. they perform electronic switching between dialing and speech. the ics operate at line voltage down to 1.6v dc (with reduced performance) to facilitate the use of more telephone sets connected in parallel. all statements and values refer to a ll versions unless otherwise specified. features z low dc line voltage: operates down to 1.6v (excluding polarity guard) z voltage regulator with adjustable static resistance z provides a supply for external circuits z symmetrical high-impedance inputs (64k ? ) for dynamic, magnetic or piezoelectric microphones z asymmetrical high-impedance input (32k ? ) for electret microphones z dtmf signal input with confidence tone z mute input for pulse or dtmf dialing - SC1062: active high (mute) - SC1062a: active low (mute) z receiving amplifier for dynamic, magnetic or piezoelectric earpieces z large gain setting ranges on microphone and earpiece amplifiers z line loss compensation (line current dependent) for microphone and earpiece amplifiers z gain control curve adaptable to exchange supply z dc line voltage adjustment facility
silicore SC1062/SC1062a shaoxing silicore technology co.,ltd www. silicore. com. cn chmc 2/15 block diagram pin connection note: pin 12 is active high (mute) for SC1062 pin description pin symbol description pin symbol description 1 ln positive line terminal 9 v ee negative line terminal 2 gas1 gain adjustment; transmitting amplifier 10 ir receiving amplifier input 3 gas2 gain adjustment; transmitting amplifier 11 dtmf dual-tone multi-frequency input 4 qr non-inverting output; receiving amplifier 12 mute mute input (see note) 5 gar gain adjustment; receiving amplifier 13 vcc positive supply decoupling 6 mic- inverting microphone input 14 reg voltage regulator decoupling 7 mic+ non- inverting microphone input 15 agc automatic gain control input 8 stab current stabilizer 16 slpe slope (dc resistance) adjustment note: pin 12 is active high(mute) for SC1062
silicore SC1062/SC1062a shaoxing silicore technology co.,ltd www. silicore. com. cn chmc 3/15 maximum values parameter symbol conditions min max. unit positive continuous line voltage v ln 12 v repetitive line voltage during switch-on or line interruption v ln(r) 13.2 v repetitive peak line voltage for a 1ms pulse per 5s v ln(rm) r9=20 ? ;r10=13 ? 28 v line current iline r9=20 ? ; note 1 140 ma positive input voltage vcc+0.7 v input voltage on all other pins v i negative input voltage -0.7 v total power dissipation p d r9=20 ? ; note 2 666 mw operating ambient temperature tamb -25 +75 c storage temperature tstg -40 +125 c junction temperature tj 125 c notes: 1. mostly dependent on the maximu m required tamb and on the vo ltage between ln and slpe 2. calculated for the maximum ambient temper ature specified (tamb=75c) and a maximum junction temperature of 125c electric characteristics unless otherwise specified: iline=11 to 140ma; v ee =0v; f=800hz; tamb=25c. characteristic symbol condition min. typ. max. unit microphone inputs mic- and mic+(pins 6 and 7) input impedance differential |zis| between mic- and mic+ 64 k ? input impedance single-ended |zis| mic- or mic+ to v ee 32 k ? common mode rejection ratio cmrr 82 db voltage gain mic+ or mic- to ln gv iline=15ma;r7=68 k ? 50 52 54 db gain variation with frequency referenced to 800hz | gvf f=300~ 3400hz ? 0.2 db gain variation with temperature referenced to 25c | gvt without r6;iline=50m a tamb=-25~+75c ? 0.2 db gain adjustment inputs gas1 and gas2 (pins 2 and 3) transmitting amplifier gain variation by adjustment of r7 between gas1 and gas2 | gv -8 0 db
silicore SC1062/SC1062a shaoxing silicore technology co.,ltd www. silicore. com. cn chmc 4/15 electric characteristics continue characteristic symbol condition min. typ. max . unit supplies ln and vcc (pins 1 and 13) iline=1ma 1.6 iline=4ma 1.9 iline=15ma 3.55 4.0 4.25 iline=100ma 4.9 5.7 6.5 voltage drop over circuit between ln and v ee v ln mic inputs open- circuit iline=140ma 7.5 v variation with temperature | v ln/ | t iline=15ma -0.3 mv/k iline=15ma; r va (ln to reg)=68k ? 3.5 voltage drop over circuit between ln and v ee with external resistor r va v ln iline=15ma; r va (reg to slpe)=39k ? 4.5 v supply current icc vcc=2.8v 0.9 1.35 ma ip=1.2ma 2.2 2.7 supply voltage available for peripheral circuitry SC1062 vcc iline=15ma mute=high ip=0ma 3.4 v ip=1.2ma 2.2 2.7 supply voltage available for peripheral circuitry SC1062a vcc iline=15ma mute=low ip=0ma 3.4 v dtmf input (pin 11) input impedance |zis| 20.7 k ? voltage gain from dtmf to ln gv iline=15ma;r7=68k ? 24 25.5 27 db gain variation with frequency referenced to 800hz | gvf f=300~ 3400hz ? 0.2 db gain variation with temperature referenced to 25c | gvt iline=50ma tamb=-25~+75c ? 0.2 db sending amplifier output ln (pin 1) iline=4ma 0.8 output voltage (rms value) v ln (rms) thd=10% iline=15ma 1.7 2.3 v noise output voltage (rms value) vno(rms) iline=15ma;r7=68k ? ; 200 ? between mic- and mic+ -69 dbmp receiving amplifier input ir (pin 10) input impedance |zis| 20 k ? gain adjustment input gar (pin 5) receiving amplifier gain variation by adjustment of r4 between gar and qr | gv -11 0 db
silicore SC1062/SC1062a shaoxing silicore technology co.,ltd www. silicore. com. cn chmc 5/15 electric characteristics continue characteristic symbol condition min. typ. max.unit receiving amplifier output qr (pin 4) output impedance |zos| 4 ? voltage gain from ir to qr gv iline=15ma;r l =300 ? (from pin9 to pin4) 29.5 31 32.5 db gain variation with frequency referenced to 800hz | gvf f=300~ 3400hz ? 0.2 db gain variation with temperature referenced to 25 c | gvt without r6;iline=50ma tamb=-25~+75c ? 0.2 db r l =150 ? 0.22 0.33 output voltage (rms value) vo(rms) thd=2%; since wave drive; r4=100k ? iline=50ma; ip=0ma r l =450 ? 0.3 0.48 v output voltage (rms value) vo(rms) thd=10%; r4=100k ? ; r l =150 ? ; iline=4ma 15 mv noise output voltage (rms value) v no(rms) iline=15ma; r4=100k ? ir open-circuit r l =300 ? 50 v mute input (pin 2) high level input voltage v ih 1.5 vcc v low level input voltage v il 0.3 v input current i mute 8 15 a reduction of gain SC1062 mute=hig h 70 db mic+ or mic- to ln | gv SC1062a mute=low 70 db SC1062 mute=hig h r4=100 k ? ; r l =300 ? -17 db voltage gain from dtmf to qr gv SC1062a mute=low r4=100k ? ; r l =300 ? -17 db automatic gain control input agc (pin 5) controlling the gain from ir to qr and the gain from mic+, mic- to ln gain control range | gv r6=110k ? (between agc and v ee ) iline=70ma -5.8 db highest line current for maximum gain iline h 23 ma lowest line current for maximum gain iline l 61 ma
silicore SC1062/SC1062a shaoxing silicore technology co.,ltd www. silicore. com. cn chmc 6/15 function description supply: vcc, ln, slpe, reg and stab power for the SC1062 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 SC1062, the supply voltage vcc 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 vcc and v ee while the internal voltage regulator is decoupled by a capacitor between reg and v ee . the dc current drawn by the device will va ry in accordance with varying values of the exchange voltage(vexch), the feed ing bridge resistance(rexch) and the dc resistance of the telephone line(rline). the SC1062 has an internal current stabilizer operating at a level determined by a 3.6k ? resistor connected between stab and v ee (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 circuitr y connected to vcc (lp) 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 =vref+i slpe *r9 or; v ln =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 v ee . in normal use the value of r9 would be 20 ? . changing the value of r9 will also affect microphone gain, dtmf gain, in control characteristics, ide-tone level, maximum output swing on ln and the dc characteristics(espe cially at the lower voltages). under normal conditions, when i slpe >= icc+0.5ma +ip, the static behavior 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.
silicore SC1062/SC1062a shaoxing silicore technology co.,ltd www. silicore. com. cn chmc 7/15 microphone inputs (mic+ and mic-) and gain pins (gas1 and gas2) the SC1062 has symmetrical inputs. its input impedance is 64k ? (2*32k ? ) and its voltage gain is typically 52db (when r7=68k ? . see fig.13). dynamic, magnetic, piezoelectric or electret (with built-in f et 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 tran sducer in use. the gain is proportional to the value of r7 which is connected between gas1 and gas2. stability is ensured by the external capaci tors, c6 connected between gas1 and slpe and c8 connected between gas1 and v ee . the value of c6 is 100pf but this may be increased to obtain a first-order low-pass f ilter. 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 high level at mute enables dtmf i nput and inhabits the microphone inputs and the receiving amplifier inputs; a low level or an open circuit does the reverse. switching the mute input will cause negligible click is at the telephone outputs and on the line. in case the line current drops belo w 6ma(parallel operation of more sets) the circuit is always in speech condition independent of the dc level applied to the mute input. (SC1062a pin12 is mute) dual-tone multi-frequency input (dtmf) when the dtmf input is enabled dialing tones may be sent onto the line. the voltage gain from dtmf to ln is typically 25.5db(when r7=68k ? ) and varies with r7 in the same way as the microphone gain. the signaling tones can be heard in the ear piece at a low level (confidence tone).
silicore SC1062/SC1062a shaoxing silicore technology co.,ltd www. silicore. com. cn chmc 8/15 receiving amplifier (ir, or and gar) the receiving amplifier has one input (ir) and a non-inverting output (or). ear piece arrangements are illustrated in fig.11 . the ir to or gain is typically 31db (when r4=100k ? ). it can be adjusted between 20 and 31db to match th e sensitivity of the transducer in use. the gain is set with the value of r4 which is connected between gar and or. the overall receive gain, between ln and or, is cal culated substracting the anti-sidetone network attenuation (32d b) 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 increas ed 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 amp lifier 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 5.8db which corresponds to a line length of 5km for a 0.5mm diameter twisted pair copper cable with a dc resistance of 176 ? /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 the anti-sidetone network, r1//zline, r2, r3, r8, r9 and zbal, (see fig.4) suppresses the transmitted signal in the ear piece. compensation is maximum when the following conditions are fulfilled: (a) r9*r2=r1[r3+(r8//zbal)]; (b) [zbal/(zbal+r8)]= [zline/(zline+r1)];
silicore SC1062/SC1062a shaoxing silicore technology co.,ltd www. silicore. com. cn chmc 9/15 if fixed values are chosen for r1, r2, r3 and r9 then condition (a) will always be fulfilled when r8/zball << r3. to obtain optimum side-tone suppression condition (b) has to be fulfilled which results in: zbal=(r8/r1) zline=k*zline where k is a scale factor; k=(r8/r1). the scale factor (k), dependent on the value of r8, is chosen to meet following criteria: (a) compatibility with a standard capac itor from the e6 or e12 range for zbal, (b) | zbal//r8 | << r3 fulfilling condition (a) and thus ensuring correct anti-sidetone bridge operation, (c) | zbal+r8 | >>r9 to avoid influencing the transmitter gain. in practice zline varies considerably with the type and length. the value chosen for zbal should therefore be for an averag e line length thus giving optimum setting for short or long lines. example the balance impedance zbal at which the optimum suppression is present can be calculated by: suppose zline =210 ? +(1265 ? //140nf) representing a 5km line of 0.5mm diameter, copper, twisted pair cable matched to 600 ? (176 ? /km; 38nf/km). when k=0.64 then r8=390 ? , zbal=130 ? +(820 ? //220nf). at line currents below 9ma the internal refere nce voltage is automatically adjusted to a lower value (typically 1.6v at 1ma). 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 1.6v. with line currents below 9ma the circuit has limited sending and receiving levels. the internal re ference 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 an d when connected between reg and slpe will increase the internal reference voltage. current (ip) available from v cc for peripheral circuits depends on the external components used. fig.9 shows this current for vcc > 2.2v. if mute is low when the receiving amplifier is driven the availa ble current is further reduced. current availability can be increased by connecting th e supply ic (1081) in parallel with r1, as shown in fig.16(c), or, by increasing the dc line voltage by means of an external resistor (r va ) connected between reg and slpe.
silicore SC1062/SC1062a shaoxing silicore technology co.,ltd www. silicore. com. cn chmc 10/15 the anti-sidetone network for the SC1062 family shown in fig.4 attenuates the signal received from the line by 32db before it enters the receiving amplifier. the attenuation is almost constant over the whole audio frequency range. fig.5 shows a conventional wheat stone bridge anti-sidetone circuit that can be used as an alternative. both bridge types can be used with either resistive or complex set impedance. fig.4 equivalent circuit of SC1062 fig.5 equivalent circuit of an anti-sidetone anti-sidetone bridge network in a wheat stone bridge configuration fig.6 SC1062 safe operating area
silicore SC1062/SC1062a shaoxing silicore technology co.,ltd www. silicore. com. cn chmc 11/15 fig.9 typical current ip available from v cc peripheral circuitry with vcc>=2.2v. curve (a) is valid when the receiving amplifier is not driven or when mute =high .curve(b) is valid when mute=low and the receiving amplifier is driven; vo(rms)=150mv,r l =150 ? . the supply possibilities can be increased simply by setting the voltage drop over the circuit v ln to a high value by means of resistor r va connected between reg and slpe.
silicore SC1062/SC1062a shaoxing silicore technology co.,ltd www. silicore. com. cn chmc 12/15 (a) magnetic or dynamic microphone. the resistor marked (1) may be connected to decrease the terminating impedance. (b) electret microphone. (c) piezoelectric microphone. fig. 10 alternative microphone arrangement (a) dynamic ear piece. (b) magnetic ear piece. the resistor marked (1) may be connected to prevent distortion (inductive load) (c) piezoelectric ear piece. the ear piece marked (2) is required to increase the phase margin (capacitive load) fig.11 alternative receiver arrangement fig.12 variation of gain with lin e current, with r6 as a parameter
silicore SC1062/SC1062a shaoxing silicore technology co.,ltd www. silicore. com. cn chmc 13/15 . rexch ? ? ? 400 600 800 1000 r6 ? k ? ? 36 100 78.7 48 140 110 93.1 82 ve x c h ? v ? 60 120 102 table 1 values of resistor r6 for optimum line loss compensation, for various usual values of exchange supply voltage (vexch) and exchange feeding bridge resistance (rexch);r9=20 ? test circuit fig.13 test circuit defining voltage gain of mic+, mic- and dtmf inputs. voltage gain is defined as: gv=20*log (| vo/vi|). for measuring the gain from mic+ and mic- the mute input should be low or open-circuit, for measuring the dtmf input mute should be high .inputs not under test should be open-circuit. SC1062a pin12 is mute
silicore SC1062/SC1062a shaoxing silicore technology co.,ltd www. silicore. com. cn chmc 14/15 fig.14 test circuit for defining voltage gain of the receiving amplifier. voltage gain is defined as: gv=20*log(|vo/vi|). SC1062a pin12 is mute application circuit fig.15 typical application of the SC1062, shown here with a piezoelectric ear piece and dtmf dialing. the bridge to the left, the zener diode and r10 limit the current into the circuit and the voltage across the circuit during line transients. pulse dialing or register recall required a different protection arrangement. the dc line voltage can be set to a higher value by resistor r va (reg to slpe) . SC1062a pin12 is mute
silicore SC1062/SC1062a shaoxing silicore technology co.,ltd www. silicore. com. cn chmc 15/15 fig.16 typical applications of the SC1062 (simplified) the dashed lines show an optional flash (register recall by timed loop break). SC1062a pin12 is mute

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