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application note tea7092 - telephone set integrated circuit AN848/1096 contents pages i. tea7092 general information ...................................... 3 i.1. setting the tea7092 application . . . . . . . . . . . . . . . . . ................... 3 i.2. pinout. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................. 4 i.3. block diagram . . . . . . . . . . . . . . . . . . . . . . . . ............................. 5 i.4. input/ouput configurations . . . . . . . . . . . . . .......... ................ 6 ii. speech feature ................................. ................... 14 ii.1. dc characteristics . . . . . . . ......................................... 14 ii.1.1. tea7092 dc voltage . . . . . . . . . . ......................................... 14 ii.1.2. telephone set dc voltage . . .......................... ................... 14 ii.1.3. start up characteristics . . . . . . . . ......................................... 15 ii.1.4. further information (v cc /v ref /i ref /v mc /v rmc /v ls/ v refl ) ....... ................ 17 ii.2. impedance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ................... 18 ii.3. transmit channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ................... 19 ii.3.1. general information - maximum gain adjustment . . . . . . . . . . . . . . . . . . . . . . ....... 19 ii.3.2. softclipping threshold (maximum line level). . . . . . . . . . . . . . ................... 20 ii.3.3. line loss compensation a.g.c. adjustment . . . . ............................. 21 ii.3.4. a.g.c. inhibition . . . . . . . . . . . . . . ......................................... 21 ii.3.5. transmit squelch / antiacoustic feedback stage. . . . .......... ................ 22 ii.4. sidetone . . . . . . . . . . . . . . . . . . ......................................... 23 ii.4.1. general information . ................................................... 23 ii.4.2. one sidetone network principle . . . . . . . . . . . . . . . . . . . . . . . . ................... 24 ii.4.3. line tracking sidetone network principle. . . . . . . . . . . . . . . . . ................... 24 ii.4.4. sidetone programming for pabx application ................................. 25 ii.5. receive channel . . . . . . . . . . ......................................... 26 ii.5.1. general information - maximum gain adjustment . . . . . . . . . . . . . . . . . . . . . . ....... 26 ii.5.2. maximum output level . . . . . .......................... ................... 27 ii.5.3. line loss compensation / a.g.c. adjustment . . . . . . . . . . . . . ................... 30 ii.5.4. a.g.c. inhibition . . . . . . . . . . . . . . ......................................... 30 ii.5.5. +6db mode . ................. ......................................... 30 ii.6. handsfree interface. . . . . . . . . . . . . . . . . . ............................. 30 iii. call progress monitor and group listening modes ............... 31 iii.1. general information. . . . . . . . ....................................... 31 iii.2. loudspeaking part supply . . ....................................... 32 iii.3. softclipping stage. . . . . . . . ......................................... 33 iii.4. antiacoustic feedback features . . . . . . ............................. 33 iii.5. maximum output power. . . . . . . . . . . . . . . . . . . . . . ....................... 35 iii.6. external power supply facility. . . . . . . ............................. 36 iii.7. ring melody control mode. . . . . . . . . . . . ............................. 37 iii.8. beep error generator . . . . . . . . . . . . . . . . . . . . . . . . . . ................... 38 1/57
contents (continued) pages iv. microcontroller interface ....................................... 39 iv.1. microcontroller power supply . . . . . . ............................. 39 iv.2. reset and pon signals . . . . . . ....................................... 39 iv.3. serial bus interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . ................... 41 iv.3.1. different codes . ....................................................... 41 iv.3.2. software example . . . . . . . . . . . . . ......................................... 45 iv.3.3. serial bus codes actions on switches . . . . . . . . . ............................. 46 iv.4. ring indicator / line current variation indicator . . . . . . . . . . . . . . . . . . 47 iv.5. oscillator . . . ............. ......................................... 47 iv.6. microcontroller signal control in the different modes. . . . . . . . . . 47 v. dialer features ............ ....................................... 48 v.1. dtmf dialer . ....................................................... 48 v.2. sine wave generator. . . . . . ......................................... 49 v.3. pulse dialer interface . . . . . . . . . . . . . . . . . . . . . . . . . . ................... 49 vi. ringer features ............ ....................................... 50 vi.1. ringer power supply. . . . . . . . ....................... ................ 50 vi.2. start up threshold level . . . . . . . . . . . . . ............................. 50 vi.3. ring frequency generator . ....................................... 51 vi.4. output power optimization . . . . . . . . . . . ............................. 51 vi.4.1. switch mode power supply concept . . . . . . . . . . . . . . . . . . . . . . . . . . ............. 51 vi.4.2. switch mode power supply losses . . . . . . . . . . . ............................. 52 vi.4.3. output power adjustment . . . . . . . . . ....................................... 53 vi.5. microcontroller management. . . . . . . . . . . . . . . . . . ................... 54 vi.6. ring software . . . . . . . . . . . . ......................................... 55 vii. application diagram ............................................... 56 tea7092 - telephone set integrated circuit 2/57
i - tea7092 general information i.1 - setting the tea7092 application tea7092 is a telephone set integrated circuit de- signed to meet various country's requirements. tea7092 is adapted to each country through ex- ternal component value modifications. tea7092 performs the following features : - speech (line interface & 2 wires / 4 wires) - call progress monitor (exchange tone heard in the loudpeaker & on-hook dialing) - group listening (handset & loudspeaker used simultaneously) - handfree interface - ring on loudspeaker - dtmf dialing - dc mask in pulse dialing mode (tip & ring voltage reduced during make period) - microcontroller interface - line current variation detector for transfer - waiting melody generator - beep error generator all these features can be programmed by the as- sociated microcontroller through the serial bus in- terface. make a copy of the last page of this document and keep it as a reference, when you read this application note, if you want to refer to the external component names. when setting the application, it is preferable to respect the following flow chart : speech part and dtmf dialing - start your application with the default component values given at the last page of this document (typical application). - adjust the dc and start-up characteristics . - adjust the impedance (return loss). - adjust the transmit parameters (softclipping level, gain, frequency response curve). - adjust the sidetone network(s) *. - adjust the receive parameters (gain, frequency response curve)*. - adjust the dtmf output level . * each of these two adjustments is influenced by the other one, for more information, see sections ii.4 & ii.5. call progress monitor and group listening - adjust the loudspeaking amplifier (gain, fre- quency response curve) without handsetconnec- tion in order to avoid influence of the handset microphone. - adjust the antiacoustic feedback efficiency . ringer part - choose the ring frequency melody . - adjust the ring start up level . - optimize the loudspeaker output power . further features - tip & ring dc value in the make period in pulse dialing mode, - line current variation detector for transfer, - waiting melody generator, - beep error generator, - microcontroller interface, are essentialy software programming. note : throughout the application note, i l is the current which power supplies the complete appli- cation (current is equivalent to the one delivered by an exchange to power a telephone set). for the entire application note, unless otherwise specified, the component values are those given at the last page of this document (typical application). tea7092 - telephone set integrated circuit 3/57
i.2 - pinout pin n name function 1v ls loudspeaker power supply 2v mc unregulated microcontroller power supply 3v l transmit output stage 4v refl loudspeaker reference voltage (v ls /2) 5 lsin loudspeaker amplifier input 6 lssof loudspeaker softclipping time constant 7 dtmf1 dtmf filter 1 8v rmc stabilized microcontroller power supply 9 osc oscillator input 10 ri/vi ring indicator/line current variation indicator output (*) 11 reset microcontroller reset output (*) 12 pon line current indicator output (*) 13 clk serial bus clock input (*) 14 data serial bus data input (*) 15 snsl short line sidetone network 16 snll long line sidetone network 17 asq anti-acoustic feedback and squelch time constant 18 asc dc offset anti-acoustic feedback and squelch amplifier suppression 19 recin receive input and positive line voltage 20 reout receive output for handfree interface and loudspeaker input 21 gtr transmit gain adjustment 22 hfin handfree microphone input referenced to v ref 23 mic1 microphone input 1 referenced to v ref 24 mic2 microphone input 2 referenced to v ref 25 v ref speech reference voltage (v cc /2) 26 v cc speech power supply 27 tsoft transmit softclipping time constant 28 softl transmit softclipping level adjustment 29 i ref resistor to set reference current 30 v s active inductor and dc characteristic adjustment 31 slpe dc mask slope adjustment 32 agnd analog ground and negative line voltage 33 i ll long line speech control gain adjustment (gmax) 34 i sl short line speech control gain adjustment (gmax - 6db) 35 ear+ positive earphone output 36 ear- negative earphone output 37 grec receive gain adjustment 38 v zp switch mode power supply internal zener 39 swp switch mode power supply output 40 rsu ring start up level 41 rco ring power output control 42 dtmf2 dtmf filter 2 43 gnd power ground and negative line voltage 44 lsout loudspeaker output * logic interface. i - tea7092 general information (continued) tea7092 - telephone set integrated circuit 4/57
29 1 3 4 6 15 16 19 26 30 dc caracteristic i&v references 25 31 5 20 37 ildc ildc sidetone mixer agc v ref mute earphone -1 amplifier 36 35 agc control versus line current 27 28 24 23 a=10 22 hand-free squelch anti-howling g=200 17 18 dc cut mute & dtmf 1/rgt 21 33 34 32 43 i-dac lf i-dac hf side code v ref beef 742 loudspeaker current supply & out tx ildc 82.ilac i(vls) ilac+dc ildc ilac+dc rx & tx dtmf hold i line sensing status ildc logic ctrl v ls /2 agc digital volume control 7 steps 4db mux gtl -10 -15 -20 -25db power agc inputs dc bias sat detect 200 m a loudhearing 44 power current extractor (3ma) serial dc regulator pon & reset control logic microcontroller serial interface 14 13 10 11 12 8 2 mute ildc 9 logic control output power ring signal optimisation ring indicator control switch mode power supply ring 39 40 41 38 v ls gmax-gtl tea7092 v ref i ref slpe lsin reout grec ear- ear+ earphone asq asc softl tsoft mic2 mic1 micro hfin gtr c21 rgt ill isl agnd gnd dtmf1 dtmf2 gnd 0v v mc v rmc v rmc pon resetn data clk ri/vi osc 3.58mhz v cc line v s recin v l snsl snll v cc zall zasl v ls v ls v refl lssof gnd 0v gnd 0v lsout loudspeaker v zp rco gnd 0v rsu +ring swp gnd 0v gnd 0v v ls v cc /2 ring melody generator oscillator tx amp softclipping v l agc AN848-01.eps i - tea7092 general information (continued) i.3 - block diagram tea7092 - telephone set integrated circuit 5/57
25 100k w 100k w ip internal amp-op current supply 26 c8 + c14 + 1ma v ref v cc 29 i ref r2 30k w internal i ref 300mv r10 r11a + r11b 3 v l from line the sum of all the currents on pin 26 (v cc ) is equal to 1.3ma (without ac receive signal) AN848-02.eps figure 1 : v ref (pin 25) : transmit and receive reference voltage (v cc /2) v cc (pin 26) : transmit and receive power supply i ref (pin 29) : internal reference current 30 c11 225k w v s v cc r3 31 slpe r12 3 v l mirror 1.5 1 i l /85 (to transmit channel) v cc 50 m a v cc 11 m a kil = i l - 5.6ma rslope = r3/55 v l = r12 x (40 + 0.5 x i l )e -6 + rslope (i l - 5.6) e -3 ;i l in ma (for i l < 20ma) v l =v l (at 20ma) + rslope x (i l -20) e -3 ;i l in ma (for i l > 20ma) 1016 kil = i l - 5.6ma 1016 AN848-03.eps figure 2 : slpe (pin 31) : dc mask slope v s (pin 30) : shunt regulator i - tea7092 general information (continued) i.4 - input / output configurations tea7092 - telephone set integrated circuit 6/57
3 v l 10 w 400w itx/41 (see transmit channel) 1 v ls + c1 i start switch on if : reset low & kil info for pon & reset v bandgap 470k w 8 v rmc c15 + 3 v l 50 w 2k w 30 to 75 m a 2 v mc + c10 0.8ma (il = 4ma) to 3ma (il > 20ma) 6v 6v AN848-04.eps figure 3 : v ls (pin 1) : loudspeaker part power supply v mc (pin 2) : unregulated microcontroller power supply v rmc (pin 8) : stabilized microcontroller supply for agc control v cc i ll (pin 33) or i sl (pin 34) r18 or r19 300mv r19 = 300 i sl - 5.6 r18 = 300 i ll - 5.6 r18 and r19 in k w ;i ll and i sl in ma r18 and r19 should be connected as close to the ground pin (agnd) as possible. AN848-05.eps figure 4 : ill (pin 33) : line current regulation start-up value isl (pin 34) : line current regulation stop value i - tea7092 general information (continued) i.4 - input / output configurations (continued) tea7092 - telephone set integrated circuit 7/57
kvlacpeak 28 softl r1 26 v cc 10 m a kvldc 2.5v 27 tsoft r4 c3 25 v ref 20 m a20 m a 23 mic1 24 mic2 25 v ref 20k w 20k w 2k w 18k w 22 hfin 0db 0db 1k w 0db 9k w earcmf 42 dtmf2 10k w 7 dtmf1 i dtmf microphone choice to anti-acoustic feedback agc 0 to -6db from anti-acoustic feedback (-9db) mute 45k w v ref 5k w i l /85 from dc path 12 21 25 v ref gtr r8 loudspeaker power supply mirror 1/40 itx/41 1 v ls c1 + itx 3 v l zb = zt//cr1//zl r1 = 5 4 x r12 - (vacpeak + 0.6) 40e -6 gtl = v mic1 (pin 23) - v mic2 (pin 24) = 20 log (820 x ) zb r8//50k w v l (pin 3) 8k w AN848-06.eps figure 5 : tsoft (pin 27) : transmit softclipping time constant softl (pin 28) : maximum ac signal (softclipping threshold) mic1/mic2 (pin 23/24) : microphone inputs hfin (pin 22) : handsfree microphone input dtmf1 (pin 7) : dtmf input and filter dtmf2 (pin 42) : dtmf filter gtr (pin 21) : transmit gain adjustment i - tea7092 general information (continued) i.4 - input / output configurations (continued) tea7092 - telephone set integrated circuit 8/57
60k w 60k w 0db kil kil = 0 for i l = isl kil = 1 for i l = ill 1 - kil agc 21 to 15db (code +6db not activated) +6db code 20 reout zal = k x zall + (1 - k) x zasl 19 recin itx 3 v l 15 snsl 16 snll c12 c27 26 v cc zasl r5+r6//c5 zall r29+r28//c28 r13 r27 r11b r11a zb r14 r17 32 grec 35 ear+ mute v cc mute v cc 36 ear- 20k w 20k w 40k w 10k w 25 v ref mute earcmf 0.6v AN848-07.eps figure 6 : snsl (pin 15) : short line length sidetone network input snll (pin 16) : long line length sidetone network input recin (pin 19) : receive input reout (pin 20) : receive output for handsfree device grec (pin 37) : receive gain adjustment ear+ (pin 35) : positive earphone output ear- (pin 36) : negative earphone output i - tea7092 general information (continued) i.4 - input / output configurations (continued) tea7092 - telephone set integrated circuit 9/57
20k w ring in 10k w volume control dc translator ls agc 40k w 5 lsin 10k w 50k w 10k w 44 lsout + c2 ls vp(lsout) v ls /2 22k w 22k w 4 v refl c20 + c1 1 v ls ri AN848-08.eps figure 7 : lsin (pin 5) : loudspeaker signal input lsout (pin 44) : loudspeaker output v refl (pin 4) : loudspeakerpart reference voltage i - tea7092 general information (continued) i.4 - input / output configurations (continued) tea7092 - telephone set integrated circuit 10/57
100k w from microphone preamplifier 0.5k w v cc 10 m a to transmit agc 0.8k w v ref 60mv attenuation programmable from 10 to 25db 17 asq r16 c16 25 v ref c25 18 asc 60mv ls agc r31 c19 6 lssof v ls vp(lsout) gnd + 0.2 v ls - 0.2 vp(lsout) 4 m a AN848-09.eps figure 8 : asq (pin 17) : anti-acoustic feedback and squelch peak voltage asc (pin 18) : anti-acoustic feedback and squelch filter lssof (pin 6) : loudspeaker softclipping time constant i - tea7092 general information (continued) i.4 - input / output configurations (continued) tea7092 - telephone set integrated circuit 11/57
r37 r35 + c6 d2 r38 c30 i(v zp ) r32 r36 v ring d3 r33 d7 t1 t2 l1 + c1 38 40 1 rsu v ls v zp 11.2v 24v 5.6v 150k w 2.6v 150k w 26khz logic control ivzp info 1.2v logic control ri v ls > 2.6v v rmc > 2.6v serial regulator 8 v rmc + c15 135k w 90k w 100 m a i/17.5k w 40k w ri 6 lssof r31 c19 ls amp (v ls - vlsout) < 0.2v 44 lsout + c2 fi ring v in ia = f{(ivzp)} 41 rco r40 c4 gain = 16 39 swp AN848-10.eps figure 9 : v zp (pin 38) : switch mode power supply internal zener swp (pin 39) : switch mode power supply output rsu (pin 40) : ring start-up level rco (pin 41) : ring power output control i - tea7092 general information (continued) i.4 - input / output configurations (continued) tea7092 - telephone set integrated circuit 12/57
internal logic ri hold v rmc 10 ri/vi i out = 1ma max AN848-11.eps figure 10 : ri/vi (pin 10) : ring indicator/line current variation clk (pin 13) or data (pin 14) v rmc f max. = 1mhz t min. between 2 bytes : 2 m s v rmc 120k w AN848-12.eps figure 11 : clk (pin 13) : clock data input data (pin 14) : data input 300k w v rmc 30pf 9 osc 30 m a 30pf AN848-13.eps figure 12 : osc (pin 9) : oscillator input internal logic information for pon/reset v rmc 12 pon v rmc 11 reset i out = 1ma max AN848-14.eps figure 13 : reset (pin 11) : m controller reset pon (pin 12) : power on output i - tea7092 general information (continued) i.4 - input / output configurations (continued) tea7092 - telephone set integrated circuit 13/57
ii - speech features ii.1 - dc characteristics ii.1.1 - tea7092 dc voltage the voltage at pin v l (pin 3) of the tea7092 is fixed by 2 external components : - r3 connectedbetween pin slpe (pin 31) and the ground which fixes the dc slope. - r12 connected betweenpin v l (pin 3) and pin v s (pin 30) which fixes the dc voltage at i l = 20ma and a part of the dc slope for i l < 20ma. the voltage at pin v l (pin 3) is equal to : for i l < 20ma : v l = r12 ? ( 40 + 0.5 ? i l ) ? 10 - 6 + r3 ? ( i l - 5.6 ) 55 ? 10 - 3 with i l in ma. for i l > 20ma : v l = v l ( 20ma ) + r3 ? ( i l - 20 ) 55 ? 10 - 3 with i l in ma, v l (20ma) is the pin v l (pin 3) dc value for i l = 20ma. ii.1.2 - telephone set dc voltage the telephone set dc voltage at line terminal is equal to (see figure 14) : v(la/lb) = v l +(r11a+r11b)xi l +v swi +v bri with : -v l : dc voltage on pin v l (pin 3) of the tea7092. -v swi : voltage across the pulse dialing switch and its protection. -v bri : voltage across the input rectifier bridge. the figures 15 to 18 give dc typical value at pin v l (pin 3) and at line terminal (la/lb) for dif- ferent value of r3 and r12. note : at the maximum line current use, the voltage at pin recin (pin 19) should be less than 11v dc , the following curves stop at the line current where they reach 11v dc at pin recin (pin 19), depend- ing of the country's application, use this information to optimize the values of r3 and r12. 3 19 30 31 32 43 agnd gnd slpe v s v l recin tea7092 r3 c11 r12 r11b r11a la lb v bri v swi AN848-15.eps figure 14 tea7092 - telephone set integrated circuit 14/57
0 20 40 60 80 100 120 i l (ma) r3 = 1.5k w 2 4 6 8 10 12 v la/lb (v) r12 = 68k w r12 = 82k w r12 = 110k w 14 AN848-18.eps figure 17 : telephone set (dc mask) ii - speech features (continued) ii.1.2 - telephone set dc voltage (continued) ii.1.3 - start-up characteristics when tea7092 goes from iddle state (on-hook) to speech mode (off-hook) the capacitor c10 connected on pin v mc (pin 2) and the capacitor c15 connected on pin v rmc (pin 8) are charged in priority, with the main part of the line current. the capacitorc10 is used to supply, through a serial regulator, the microcontroller connected on the regulated 3.5v supply, pin v rmc (pin 8). in pulse dialing, flash or earth button mode the capacitor c10 is used to supply the microcontroller, depending on the power consumption of the micro- controller and on the country's requirements for these different signal durations, it is necessary to adapt the value of c10. typical capacitor values, with a current consump- tion of 500 m a for the microcontroller : c10 = 470 m f , c15 = 4.7 m f. i l (ma) r3 = 2.7k w 0 2 4 6 8 10 12 v recin (v) r12 = 68k w r12 = 82k w r12 = 110k w 0 20 40 60 80 100 120 AN848-17.eps figure 16 : v recin (pin 19) i l (ma) r3 = 2.7k w 2 4 6 8 10 12 v la/lb (v) r12 = 68k w r12 = 82k w r12 = 110k w 14 0 20 40 60 80 100 120 AN848-16.eps figure 15 : telephone set (dc mask) i l (ma) r3 = 1.5k w 0 2 4 6 8 10 12 v recin (v) r12 = 68k w r12 = 82k w r12 = 110k w 0 20406080100120 AN848-19.eps figure 18 : v recin (pin 19) tea7092 - telephone set integrated circuit 15/57
10 w 400 w itx/41 transmit amplifier 3 19 on if reset = 0 & il present 6v 1 6v 2 istart-up = ivls 470k w 8 50 w 2 w 75 m a 3ma 19 21 20 3.5v tea7092 c1 + v ls c10 + v mc c15 + v rmc reset pon ri r11a + r11b v l recin i l mic pins 23 & 24 loudspeaker current supply vbandgap serial regulator logic block AN848-20.eps figure 19 ii - speech features (continued) v l v mc reset v rmc start-up t t t t speech AN848-21.eps figure 20 ii.1.3 - start-up characteristics (continued) figure 19 describes the start-up principle. when v rmc reaches 2.6v, the reset goes to high level, the start-up current source is inhibited and only connected to pin v ls (pin 1), to power supply the loudspeaker amplifier. the pin v rmc (pin 8) reaches its final value, 3.5v by charging the c10 on pin v mc (pin 2) and c15 on pin v rmc (pin 8) with 3ma current source and finally the voltage on pin v mc (pin 2) increases until its final value which is equal to pin v l (pin 3) minus 0.4v. figure 20 gives the start up characteristic timing. when tea7092 goes from iddle state (on-hook) to ring mode, only the 4.7 m f capacitor c15 on pin v rmc (pin 8) is charged, with iring current source, and a fast start up delay could be achieved in ring mode. tea7092 - telephone set integrated circuit 16/57
i l (ma) 0 20 40 60 80 100 i ls (ma) i ls ip ivmc 0 20 40 60 80 100 120 0 2 4 6 8 10 10 30 50 70 90 AN848-22.eps figure 21 ii - speech features (continued) ii.1.4 - further information (v cc /v ref /i ref /v mc /v rmc /v ls /v refl ) for more information on these pins see section i.4 - input/output configurations. v cc (pin 26) , v ref (pin 25) , i ref (pin 29) the v cc supplies the transmit path, handset and handfree microphone amplifiers, the receive path, earphone amplifier and the transmit squelch/antia- coustic feedback stage. the current consumption on this pin, i p , is 1.3ma at a 20ma line current (see figure 21). from the v cc supply, the v ref stage is built. v ref is used as an ac ground for all the stages powered from v cc . the output current compliance of v ref is : 1ma. the reference voltage at v ref is : v cc /2. i ref pin is used as an internal current reference. the r2 value is fixed and should not be modified. it is recommended to connect a 1% resistor value on this pin. the voltage at i ref pin has a 300mv constant value. v mc (pin 2) , v rmc (pin 8) these 2 pins supply the microcontroller. these 2 pins are connected through a serial regulator. on v mc a 470 m f capacitor is connected, this ca- pacitor is charged only when tea7092 is powered from pin v l (pin 3) (off-hook state) and is used to power supply the microcontroller during pulse dialing, flash and earth button, when the line loop is open. as described in section ii.1.3, this capacitor is quickly charged during the ostart upo condition. the dc value at v mc is : v mc =v l - 0.4v and is internally limited at 6v max. v rmc is powered from the highest dc value be- tween pin v ls (pin 1) and pin v mc (pin 2) in off-hook state or from pin v ls (pin 1) in ring mode. v rmc is a 3.5v stabilized power supply. v rmc supplies the oscillator, the logic part (micro- controller interface, error beep, and ring frequency generators) and the logic part of the d.a.c. used for the waiting melody and the dtmf generators. the current consumption on this pin is 250 m a when the oscillator is on and 50 m a when the oscillator is off code (0111010) is sent. note : to reduce the c10 value connected at pin v mc (pin 2), it is recommended to inhibit the oscillator during the pulse dialing and flash signali- zations. in ring mode only the 4.7 m f capacitor connected on pin v rmc (pin 8) is charged to achieve a short delay to generate the ring signal on the loud- speaker. v ls (pin 1) , v refl (pin 4) the v ls supplies the loudspeaker amplifier part. the current source, i ls , between the pin v l (pin 3) and the pin v ls (pin 1) gives the main part of the line current to supply the loudspeaker amplifier (see figure 21) : i ls = 0.74 x i l - 1.8ma ; for i l < 15ma i ls = 0.92 x i l - 4.5ma ; for i l > 15ma the internal current consumption on v ls is 1ma, so the current i ls1 available for the loudspeaker and other peripherals is : i ls1 =i ls - 1ma the dc value at v ls depends of the dc value at pin v l (pin 3) and is equal to : v ls (pin 1) = v l (pin 3) - (0.95 + 10 x i ls ) volts from the v ls supply, the v refl stage is built. the v refl is buffered in order to be used as an ac ground for all the stages powered from v ls . the reference voltage at v refl is : v ls /2. tea7092 - telephone set integrated circuit 17/57
ii - speech features (continued) ii.2 - impedance rpc cpc 32 26 zsh 31 30 3 19 16 15 tea7092 r3 slpe agnd v cc r12 c11 v s r11a r11b recin v l snll snsl c27 c12 cr1 r9 c9 r10 c8 v ldc +v lac r6 c5 r5 r28 c28 r29 zt zasl zall r13 r27 zimp = v lac i lac i ldc +i lac AN848-23.eps figure 22 : tea7092 application impedance zt allows the user to adjust the set impedance by changing the value of r10, r9 and c9 ; in this way the impedance can be adjusted as a real one (only r10) or as a complex one (r10, r9, c9). zall zals sidetone networks which are in parallel with zt, if the ratio : r13/r11a>>1 and r27/(r11a+r11b)>>1, zall and zasl are negligible for the impedance calculation. zic is the internal impedance of tea7092. it includes the impedance of the transmit path which is equivalent to a current source in parallel with cpc (3nf), the impedance of all the other stages which are equivalent to rpc (15k w ) and the impedance of the shunt regulator stage (ac/dc decoupling stage) made on pin 30 (v s ). tea7092 application impedance is : zimp = zt//zic//(zall + r11a + r11b) //(zasl + r11a)//cr1 as it will be describe in section ii.4, the sidetone networks are equal to : zall = r27 r11a + r11b ? ( zt//cr1// zll ) zasl = r13 r11a ? ( zt// cr1 //zsl ) where zll is the long line impedance, and zsl is the short line impedance. if r27/(r11a+r11b) and r13/r11a are higher than 100 (r27 and r13 = 3.3k w ): zall and zasl >> zt and : zimp = zt//zic//cr1 figure 24 and the table 1 give the tea7092 appli- cation characteristics at i l = 40ma. table 1 ( ri = 20 ? log [zimp + 600] [zimp - 600] ) frequency (hz) real part () imaginary part () module () phase (deg) return loss [rl] (db) 200 550 80 556 8 21.7 300 573 67 577 7 24.2 800 604 22 605 2 34.6 1 000 606 12 607 1 38.8 1 500 608 -5 608 0 42.1 2 500 606 -28 607 -3 32.6 3 500 603 -43 605 -4 28.8 5 000 597 -67 601 -6 25 7 000 589 -94 596 -9 22 9 000 579 -119 591 -12 19.8 12 000 560 -154 581 -15 17.3 8 12 16 20 24 28 32 36 40 0.1 0.2 0.3 0.5 1 2 3 5 10 f (khz) ri (db) i l = 20ma i l = 100ma country limit request AN848-25.eps figure 24 : return loss rslp lsh zsh = r3 + (j x 2 x p x f x r3 x r12 x c11) 55 regulator shunt impedance AN848-24.eps figure 23 : zsh impedance tea7092 - telephone set integrated circuit 18/57
ii - speech features (continued) ii.3 - transmit channel ii.3.1 - general information (maximum gain adjustment) the transmit path amplifies several signals : - the handset microphone. - the handfree microphone. - the dtmf sinewave. - the waiting melody sinewave. at one time, only one of these signals is amplified, the choice is made through the serial bus intercon- nected with the microcontroller. figure 25 gives the transmit channel block dia- gram. the first switch selects the microphone used. the signal coming from the handset microphone, pins mic1 & mic2 (pins 23 & 24) is limited by the softclipping stage, more details are given in sec- tion ii.3.2 osoftclipping thresholdo on this stage. its gain depends on the gain control stage program- ming, more details are given in section ii.3.3 oline loss compensation a.g.c. adjustmento. its abso- lute value is adjusted on the final stage with pin gtr (pin 21). the output signal of the handset microphone pre- amplifier is used for the squelch feature. c32 23 mic1 24 mic2 25 v ref 20k w 20k w 2k w 18k w 22 hfin 0db 0db 1k w 0db 9k w 42 dtmf2 10k w 7 dtmf1 i dtmf or i sinwave microphone choice agc 0 to -6db mute 45k w v ref 5k w i l /85 from dc path 12 21 25 v ref gtr r8 loudspeaker current source mirror 1/40 itx/41 v ls c1 + itx gtl = 20 log (820 x ) zb r8//50k w c13 1 c14 + to loudspeaker amplifier 17 18 c25 c16 r16 asq asc 27 28 r4 tsoft softl r1 c3 softclipping stage 3 v l 19 recin r11a + r11b zb = zt//cr1//zl i l tea7092 anti-acoustic feedback stage AN848-26.eps figure 25 : transmit channel block diagram tea7092 - telephone set integrated circuit 19/57
ii - speech features (continued) ii.3 - transmit channel (continued) the second switch selects the microphone signal, the mute mode, the dtmf mode or the sinewave mode (waiting frequency). the maximum transmit gain, gtl is fixed by r8 connected on pin gtr (pin 21) and is equal, on pin v l (pin 3) to : gtl = 20 ? log ? ? ? 820 ? zt// cr1 //zl + ( r11a + r11b ) r8//50k w ? ? ? zimp is the complete telephone set application and zl is the line impedance. 50k w is the value of the integrated resistor connected between the pin gtr (pin 21) and the pin v ref (pin 25). if it is necessary, to have a steady gain over the frequency range 300hz to 3.4khz, r8 can be re- placed by a complex network : r8 + r7//c7. the final amplifier stage is the louspeaker current source supply, which is modulated by the transmit signal, therefore no significatif line current is used for the transmit path, and the current source supply for the loudspeaker part versus the line current is always optimized. ii.3.2 - softclipping threshold (maximum line level) the softclipping stage limits the transmit level on line. this level is limited in two ways : the transmit negative part of the sinewave is com- 25 v ref 20k w 20k w 24 23 microphone preamplifier mic1 mic2 20 m a v cc 27 tsoft v l(dc) -v l(acp) v l(dc) - 2.5v 20 m a v cc kv l(acp) 28 softl v cc 10 m a 3 v l rest of the transmit channel r4 c3 c14 + r1 u/i converter tea7092 AN848-27.eps figure 26 : softclipping stage pared to 2.5v dc . this limitation is useful for low line current when the dc level at pin v l (pin 3) is low. this limitation is useful when two telephone sets are off-hook in parallel on the same line. on an absolute line level, this level is fixed by r1 connected on pin softl (pin 28) and depends on r12 value : vacpeak = (5 x r12 - 4 x r1) x 10 -5 - 0.6 figure 26 describes the sofclipping stage. figure 27 gives an example of the v acpeak transmit level versus line current for r12 = 82k w and r1 = 47k w . i l (ma) .5 4 6 8 10 v l (v) (pin 3) 0 20406080100 1.6v p 0.9v p AN848-28.eps figure 27 tea7092 - telephone set integrated circuit 20/57
ii - speech features (continued) ii.3 - transmit channel (continued) figure 28 gives the transmit line level at pin v l (pin 3) and the transmit distortion versus the input microphone level (pin mic1 (pin 23) & pin mic2 (pin 24)) for r12 = 82k w , r1 = 47k w & r8 = 1.62k w . i l (ma) dgtx (db) 0 20406080100 -6 -4 -2 0 r18 = 18k w r18 = 10k w r18 = 8.2k w r18 = 6.8k w r18 = 5.6k w AN848-32.eps figure 31 : dgtx = f(i l ) 0.2 0.5 1 2 5 10 20 50 100 v mic (mv rms ) 0.05 0.1 0.2 0.5 1 2 0 2 4 6 8 10 12 v la/lb (vrms) d[v la/lb ] (%) v line distortion AN848-29.eps figure 28 : tx output level & distortion (i l =20ma) figure 29 gives the maximum transmit level at pin v l (pin 3) versus r1, for r3 = 2.7k w & for different values of r12, at i l = 40ma. ii.3.3 - line loss compensation/ a.g.c. adjustment the tea7092 uses a line current information to control the transmit and receive gains variation versus the line current. the automaticgaincontrol (a.g.c.)versus line length works in the same way for transmit and receive paths. through two external resistors the line current vari- ation, where the a.g.c. occurs, is programmable : - r18 connected on pin ill (pin 33) sets up the start up line current value, i ll , for the a.g.c. r18 = 300 i ll - 5.6 in k w ;i ll in ma - r19 connected on pin isl (pin 34) sets up the slope and the line current value, i sl , where the transmit and receive gains are equal to the maxi- mum gain value minus 6db. r19 = 300 i sl - 5.6 in k w ;i sl in ma for line current values lower than i ll , the transmit and receive gains stay at their maximum values. for line current values upper than i sl , the transmit and receive gains stay at their minimum values. figure 30 gives a.g.c. with a constant start value (i l = 20ma) and different values of r19. figure 31 gives a.g.c. with a constant stop value (i l = 100ma) and different values of r18. r1 (k w ) 0 0.25 0.5 0.75 1 1.25 v la/lb (v) 1.5 0 20406080100120 1.75 2 2.25 2.5 2.75 3 3.25 r12 = 68k w r12 = 82k w r12 = 110k w AN848-30.eps figure 29 : vac max on line ii.3.4 - a.g.c. inhibition the a.g.c. feature can be inhibited through the serial bus interface by sending the code 0010100. this code is a toggle one. when the no a.g.c. mode is selected the transmit and receive gains stay at their maximum values -2db over the line current range variation. this feature is used for a telephone set connected behind a pabx or in a country where the a.g.c. feature is not requested. i l (ma) dgtx (db) 0 20406080100 -6 -4 -2 0 r19 = 8.2k w r19 = 6.8k w r19 = 4.7k w r19 = 3.9k w r19 = 3.3k w AN848-31.eps figure 30 : dgtx = f(i l ) tea7092 - telephone set integrated circuit 21/57
ii - speech features (continued) 100k w 0.5k w from microphone preamplifier 0.8k w v ref 60mv to transmit agc ls agc 60mv 17 asq 25 v ref 18 asc r16 tea7092 c16 c25 10 m a v cc AN848-33.eps figure 32 : block diagram v mic (dbv) (pins 23 & 24) gtl (db) -56 -60 -64 38 40 44 -68 -72 -76 -80 36 42 c25 = 100nf c25 = 470nf c25 = 1 m f AN848-35.eps figure 34 : squelch threshold (i l = 20ma/f mic =1khz) ii.3.5 - transmit squelch / antiacoustic feedback stage the same stage is used for the transmit squelch and the antiacoustic feedback feature which is used in loudspeaking mode. figure 32 shows the block diagram of this stage. when there is no signal on the handset microphone inputs, the transmit gain is reduced by 9db, refer to the maximum gain, and the loudspeaker ampli- fier is at the gain value set by the volume control stage, (see section iii - call progress moni- tor and group listening modes). when the handset microphone signal is present and in- creases progressively, it describes the first curve in figure 33 and the loudspeaker amplifier describes the second curve in figure 33. the attenuationof the loudspeaker amplifier for the antiacoustic feature is programmable from 10db to 25db through the serial bus interface, the default value is 15db. the squelch thresholdfeature can be inhibited through the serial bus interface by sending the code (0011001) with- out affectingthe antiacousticfeedback control. this code is a toggle one. the squelch threshold level is adjustable through the c25 capacitor value con- nected at pin asq (pin 18). be aware that when the threshold level is modified, the cut-off frequency of the filter is also modified. the squelch threshold level is determined by the microphone level injected at pins mic1 & mic2 (pins 23 & 24). figure 34 gives the threshold level with a maximum transmit gain of 44db. normal speech x is programmable through the serial bus (10, 15, 20, 25db) (default value is 15db) low microphone level gmax gmax - 9.5db * 60mv at pin 17 * gls gls - xdb vsl vst vsoft gtx (db) gls is programmable through the volume control stage v mic high microphone signal softclipping mode v mic 9db 3db AN848-34.eps figure 33 tea7092 - telephone set integrated circuit 22/57
ii - speech features (continued) ii.4 - sidetone ii.4.1 - general information itx tea7092a v l rx zb = zt//cr1//zl zal to earphone i l v1 recin sn tea7092 v1 - v2 ry v1 = v2 if zal = x zb ry rx v2 AN848-36.eps figure 35 the sidetone uses the wheatstone bridge principle (see figure 35). figure 36 shows the block diagram of the sidetone stage. tea7092 integrates a line tracking sidetone net- work which uses two sidetone networks. one sidetone network, zall, is optimized for a long line length connection and the other one, zasl, is optimized for a short line length connec- tion. an internal mixer stage uses a line current information, kil, to smooth linearely from zall to zasl with the following equation : zal = k x zall + (1 - k) x zasl k = 1 for i l =i ll , k = 0 for i l =i sl and k varied linearly between 1 and 0 when the line current varied from i ll to i sl . like this, the sidetone is optimized for every line length. this concept can be suppressed by shortcircuiting the two sidetone inputs, pin snll (pin 16) and pin snsl (pin 15) and to connect only one side- tone network, in this case the sidetone is only optimized for one line length, as a standard one, and the efficiency of the sidetone is lower on all the other line length connections. 60k w 60k w 0db kil kil = 0 for i l =i sl kil = 1 for i l =i ll 1 - kil agc 21 to 15db (code +6db not activated) +6db code 20 reout zal = k x zall + (1 - k) x zasl 19 recin itx 3 v l 15 snsl 16 snll c27 c12 26 v cc zasl r5+r6//c5 zall r29+r28//c28 r13 r27 zbl or zbs tea7092 r11b r11a + c8 0.6v AN848-37.eps figure 36 tea7092 - telephone set integrated circuit 23/57
ii - speech features (continued) 60k w 60k w 0db kil kil = 0 for i l =i sl kil = 1 for i l =i ll 1 - kil agc 21 to 15db (code +6db not activated) +6db code 20 reout zal = k x zall + (1 - k) x zasl 19 recin itx 3 v l 15 snsl 16 snll c12 26 v cc zasl r5+r6//c5 r13 zb tea7092 r11 + c8 0.6v AN848-38.eps figure 37 ii.4.2 - one sidetone network principle figure 37 gives the sidetone connection. the sidetone is optimized if : v1 - v2 = v recin(19) -v snsl/snll (15/16) =0 zal = r27 r11 ? zb with zb = zt//cr1//zl. figure 38 gives the sidetone efficiency versus the line length. in receive mode the signal v1-v2 is amplified through the receive path. the attenuationdue to the external components of the sidetone stage is : gsid = v1 - v2 v1 = r11 + r27 r11 + r27 + zal if, r27 = k1 x r11 and k1 >> 1 : gsid = v1 - v2 v1 = r11 r11 + zb the sidetoneattenuationis proportionalto r11 andzb. ii.4.3 - line tracking sidetone principle figure 39 gives the sidetone connection. the sidetone are optimized if : v1 - v2 = 0 - on long line connection : v1 - v2 = v recin (19) -v snll (16) =0 ? zall = r27 r11a + r11b ? zbl with zbl = zt//cr1//zll. - on short line connection : v1 - v2 = v recin (19) -v snsl (15) =0 ? zasl = r13 r11a ? zbs with zbs = zt//cr1//zsl. zll is the long line length impedance and zsl is the short line length impedance. figure 40 gives the sidetone efficiency versus the line length for a one sidetone network principle and a tracking sidetone network principle. vear high low 01234 line (km) AN848-39.eps figure 38 tea7092 - telephone set integrated circuit 24/57
ii - speech features (continued) ii.4 - sidetone (continued) 60k w 60k w 0db kil kil = 0 for i l =i sl kil = 1 for i l =i ll 1 - kil agc 21 to 15db (code +6db not activated) +6db code 20 reout zal = k x zall + (1 - k) x zasl 19 recin itx 3 v l 15 snsl 16 snll c27 c12 26 v cc zasl r5+r6//c5 zall r29+r28//c28 r13 r27 zbl or zbs tea7092 r11b r11a + c8 0.6v AN848-40.eps figure 39 in receive mode the signal v1-v2 is amplified through the receive path. the attenuationdue to the external components of the sidetone stages are : - for a line current equivalent to a long line con- nection : gsid ( l )= v1 - v2 v1 = r11a + r11b + r27 r11a + r11b + r27 + zall if, r27 = k1 x (r11a + r11b) and k1 >> 1 : gsid ( l )= v1 - v2 v1 = r11a + r11b r11a + r11b + zbl the sidetone attenuation is proportional to (r11a + r11b) and zbl. - for a line current equivalent to a short line con- nection : gsid ( s )= v1 - v2 v1 = r11a + r13 r11a + r13 + zasl if, r13 = k1 x r11a and k1 >> 1 : gsid ( s )= v1 - v2 v1 = r11a r11a + zbs the sidetone attenuation is proportionnal to r11a and zbs. r11a and r11b should be calculated to have the same attenuation due to the two sidetone net- works. in this way the complete receive channel gain is fixed on pin grec (pin 43) and in a.g.c. mode the receive gain is reduced by 6db between i ll , line current for a long line connection, and i sl , line current for a short line connection. if an application requests less or more than 6db on the complete receive channel,the values of r11a and r11b will be adapted to it. ii.4.4 - sidetone programmating for pabx application when the tracking sidetone network is used, it is possible to inhibit it through the serial bus interface. this principle suppresses the switches existing in a telephone set, when this one can be indifferently connected to a public exchange or a private ex- change. when it is connected on a publicexchange the tracking sidetone network is used. when it is connected on a private exchange the tracking side- tone network is inhibited, internally the kil informa- tion which controls the sidetone mixer stage is fixed independently of the line current value, and can take two values : - by sending the code 0011000, the sidetone net- work is equivalent to : zal = 3 4 ? zall + 1 4 ? zasl - by sending the code 0011011, the sidetone net- work is equivalent to : zal = zasl vear high low 01234 line (km) one sidetone network tracking sidetone AN848-41.eps figure 40 tea7092 - telephone set integrated circuit 25/57
ii.5 - receive channel ii.5.1 - general information (maximum gain adjustment) ii - speech features (continued) 60k w 60k w reout 19 recin 15 snsl 16 snll c12 c27 26 v cc zasl r5+r6//c5 zall r29+r28//c28 r13 r27 v l tea7092 r11b r11a + c8 r14 r17 32 grec 35 ear+ mute v cc mute v cc 36 ear- 20k w 20k w 40k w 10k w mute i l 20 21 to 15db sidetone mixer & agc stages a2 25 v ref c14 a3 a1 37 dtmf c13 idtmf or isinwave vear 0.6v AN848-42.eps figure 41 the receive path amplifies several signals : - the line signal to the earphone with an interme- diate output, pin reout (pin 20) so as to use this signal as an input for the loudspeaker ampli- fier or for a handfree circuit such as tea7540. - the dtmf sinewave as a confidence tone level. - the waiting melody sinewave as an earphone level control. at one time, only one of these signals is amplified, the choice is made through the serial bus interface with the microcontroller. figure 41 shows the receive channel block dia- gram. the signal vrecin - vsnll or vrecin - vsnsl or a combination of both is amplified to the ear- phone outputs. as described in section ii.4.2 and section ii.4.3 the signal v1 is attenuated through the sidetone net- work. after this attenuation, the received signal is amplified by the sidetone mixer and a.g.c. stages with an amplification, of 21db on a long line length, i ll , which is the maximum receive gain, and of 15db on a short line length, i sl , when the a.g.c. feature is used. the final gain adjustment is done on pin grec (pin 20) by adjusting r14 and r17 values. tea7092 - telephone set integrated circuit 26/57
ii - speech features (continued) ii.5 - receive channel (continued) the gain between pin recin (pin 19) and the earphone outputs, pin ear+ (pin 35) and pin ear- (pin 36) is : - with tracking sidetone and a.g.c. features, ear- phone connected in symmetric mode : ? on long line, i l =i ll , maximum gain grl ( db )= 20 ? log vear v l = 20 ? log ( gsid ( l )) + 21db + 20 ? log ? ? ? 2 ? r17 r14 ? ? ? ? on short line, i l =i sl , minimum gain grs ( db )= 20 ? log vear v l = 20 ? log ( gsid ( s )) + 15db + 20 ? log ? ? ? 2 ? r17 r14 ? ? ? - with one sidetone network and a.g.c. features, earphone connected in symmetric mode : ? on long line, i l =i ll , maximum gain grl1 ( db )= 20 ? log vear v l = 20 ? log ( gsid )+ 21db + 20 ? log ? ? ? 2 ? r17 r14 ? ? ? ? on short line, i l =i sl , minimum gain grsl ( db )= grl1 - 6db it is possible to use only one output, asymmetric mode, in this case all the receive gain are reduced by 6db. figure 42 shows the asymmetric connection. note : due to the concept used to power supply the earphone through the impedance network (r10) and with the v cc supply, it is preferable to connect the earphone in asymmetric mode if the earphone impedance is less than 300 w , and in symmetric mode if the earphone impedance is more than 300 w . more details are given in the following paragraph. ii.5.2 - maximum output level the maximum output level depends on several parameters : - the dc level on pin v l (pin 3). - the impedance network value connected be- tween pin recin (pin 19) and pin v cc (pin 26). - the earphone impedance value. figure 43 shows the earphone amplifier supply principle. without ac signal the voltage at pin v cc (pin 26) is : v cc =v l + r11a/b x i l - (r10 + r11a/b) x i p the value at pin v l (pin 3) depends on r12 (see section ii.1.1). when an ac signal is amplified, the current driving the earphone, iear, flows through r10 and the dc voltage at pin v cc (pin 26) is reduced. 20 grec v ref a2 35 ear+ a3 -1 26 36 ear- + c8 v cc 37 reout from sidetone mixer r17 r14 + c24 tea7092 receive amplifier earphone AN848-43.eps figure 42 tea7092 - telephone set integrated circuit 27/57
35 36 -1 26 19 ip 330 tea7092 iear c24 iear ear+ ear- rear symmetric or asymmetric use c11 recin v cc r10 ip + iear i l + c8 i l - (ip + iear) v l v s r12 r11a/b v l (3) AN848-44.eps figure 43 ii - speech features (continued) ii.5 - receive channel (continued) with this principle the maximum output voltage at pin ear+ (pin 35) and pin ear- (pin 36), depending on the application, is limited in current and in voltage in the following way : r11 = r11a + r11b i p = 1.3ma at i l = 20ma i p = 1.7ma at i l = 60ma (see figure 21). v recin =v l (3) + r11 x (i l -i p -i ear ) and v cc =v recin -r10x(i p +i ear ) - in asymmetric use; earphone (r ear ) connected on pin ear+ (pin 35). v cc =2xv ear(peak)(max.) + 0.4 v ear ( rms ) = p ? r ear ? i ear `` 2 v ear(rms) (max.) in v rms : v ear(rms) (max.) = p ? r ear ` ` 2 ? ( 2 p ? r ear + r10 + r11 ) ? [v l + r11 ? i l - ( r10 + r11 ) ? i p - 0.4] - in symmetric use; earphone (r ear ) connected between pin ear+ (pin 35) & pin ear- (pin 36). v cc =v ear (peak)(max.) + 0.2 v ear ( rms ) = p ? r ear ? i ear 2 ? ` ` 2 v ear(rms) (max.) in v rms : v ear(rms) (max.) = p ? r ear `` 2 ? (p ? r ear + 2 ? ( r10 + r11 )) ? [v l + r11 ? i l -( r10 + r11 ) ? i p - 0.2] notes : 1. in few applications, at low line current (i l < 20ma) and depending on the dc voltage at pin v l (pin 3), the absolute minimum value of v cc , 2v, should be taken into account in the calculation of v ear(rms)(max.) . this limitation happens if : i l = 20ma, r12 = 68k w and r10 = 1200 w (complex impedance dc value). 2. usually, when the impedance of a transducer, rear, increases, the efficiency of the transducer in dbspl/v decreases. the receive gain is adapted to the earphone impedance to offset this transducer'sefficiency change, so that the complete acoustical gain of the receive path remains constant. tea7092 - telephone set integrated circuit 28/57
table 2 asymmetric symmetric r ear = 150 w r ear = 300 w r ear = 600 w r ear =1k w r17 33k w 68kw 68k w 120k w c17 680pf 330pf 330pf 220pf the table 3 gives the value of v ear(rms) (max.), at i l = 20ma & i l = 60ma, for different values of, r12 (68k w , 82k w , 110k w ), r10 (680 w , 1200 w to simulate a complex impedance), r ear (150 w , 300 w in asymmetric mode ; 600 w ,1k w in symmetric mode) and a distortion level at 2% and 10%. table 3 earphone output level ( vrms ) i l r10 r12 d (%) 150 w (a) 300 w (a) 600 w (s) 1k w (s) 20ma 680 w 68k w 2 0.45 0.77 1.2 1.5 10 0.51 0.85 1.3 1.6 82k w 2 0.45 0.9 1.4 1.8 10 0.51 0.96 1.52 1.92 110k w 2 0.46 0.98 1.91 2.4 10 0.51 1.1 2 2.56 1200 w 68k w 2 0.26 0.52 0.59 0.95 10 0.29 0.57 0.61 0.97 82k w 2 0.39 0.64 0.87 1.25 10 0.42 0.69 0.89 1.33 110k w 2 0.46 0.89 1.32 1.65 10 0.5 0.95 1.37 1.8 60ma 680 w 68k w 2 0.28 0.6 1.2 2.3 10 0.32 0.69 1.4 2.5 82k w 2 0.28 0.6 1.25 2.3 10 0.32 0.69 1.42 2.5 110k w 2 0.29 0.62 1.27 2.3 10 0.32 0.7 1.44 2.6 1200 w 68k w 2 0.28 0.6 1.23 1.9 10 0.32 0.69 1.4 1.98 82k w 2 0.28 0.6 1.25 2.15 10 0.32 0.69 1.33 2.3 110k w 2 0.29 0.62 1.28 2.3 10 0.33 0.7 1.45 2.6 the sidetone mixer stage has a limiter to avoid acoustic signal higher than 120 dbspl on the earphone. example : electrodynamic transducer : 150 w / 122 dbspl/v - r10 = 680 w ; ? at i l = 20ma : v ear(max.) = 0.51v rms ? 116.2 dbspl ? at i l = 60ma : v ear(max.) = 0.33v rms ? 112.4 dbspl if this acoustic limitation is too low, it is possible to modify it by : - decreasing the gain of the sidetone attenuation = decrease r11a & r11b. (r13 & r27 should also be modified). - increasing the gain on pin grec (pin 37), to maintain the same total receiving gain ? increase r17. ii - speech features (continued) ii.5 - receive channel (continued) tea7092 - telephone set integrated circuit 29/57
ii.5.3 - line loss compensation / a.g.c. adjustment the characteristics of the a.g.c. stage in the re- ceive path are the same as those in the transmit path. for more information see section ii.3.3. ii.5.4 - a.g.c. inhibition the characteristics of the a.g.c. inhibition stage in the receive path are the same as those in the transmit path. for more information see section ii.3.4. ii.5.5 - +6db mode through the serial bus interface, it is possible to increase the receive gain amplifier by 6db. this code (0010110) is a toggle code. ii.6 - handsfree interface figure 44 shows the interconnection between tea7092 and handsfree circuit such as tea7540. tea7092 should be in handsfree mode (0110010). the handsfree circuit is supplied through the pin v ls (pin 1) in this mode the signal injected on pin hfin (pin 22) is amplified, the antiacoustic feedback stage is inhibited and the loudspeaker amplifier is activated. the receive path of the handsfreecircuit is inserted between pin reout (pin 20) and pin lsin (pin 5). 5 lsin 20 reout 22 hfin 43 gnd 1 vls 6 lsout tea7092 26 15 3 outr inr oute 1 gnd 13 ine 28 v+ tea7540 l handfree microphone AN848-45.eps figure 44 ii - speech features (continued) tea7092 - telephone set integrated circuit 30/57
ring in 10k w ri 20k w volume control dc translator 40k w 5 ls agc 10k w 50k w 44 10k w vp(lsout) tea7092 sin lsout + c2 l AN848-46.eps figure 45 iii - call progress monitor and group listening modes iii.1 - general information the call progress monitor and group listening modes are off-hook modes with the loud- speaker being used. the call progress monitor, or oon-hook dialingo is an off-hook mode where the line is taken through a dedicated key which closes the line without using the handset. in this mode only the loudspeaker is enabled, to hear the different tones coming from the exchange. as soon as the handset is off-hook the loudspeaker is disabled and no longer used. in call progress monitor, the handset microphone is muted and the anti-acoustic feature is disabled. the group listening mode is an off-hook mode where the handset and the loudspeaker are simul- taneously used. the receive signal can be heard in the earphone and in the loudspeaker. in group listening mode, the anti-acoustic or anti-howling feature is enabledto prevent any feedbackfrom the handset microphone to the loudspeaker which can cause howling effect. figure 45 shows the loudspeaker amplifier path. the signal coming from pin reout (pin 20), inter- mediate receive output, is injected into the loud- speaker amplifier on pin lsin (pin 5). between pin reout (pin 20) and pin lsin (pin 5) a filter can be added to offset the loudspeaker frequency re- sponse curve. the loudpeaker is connected on pin lsout (pin 44). the maximum gain between pin lsin (pin 5) and pin lsout (pin 44) is 34db. when a handsfree circuit is used, its receive path is connected between pin reout (pin 20) and pin lsin (pin 5). the loudspeaker amplifier, as described in fig- ure 45, is controlled by the following signals : - ls agc from the anti-acoustic feedback stage which attenuates the loudspeaker amplifier gain when the handset microphone level goes upper the threshold to avoid howling effect. - pin lssoft (pin 6) which attenuates the loud- speaker amplifier gain, to drive properly the loud- speaker when the lsout output reaches the saturation of the output stage compared to v ls or the ground, through v pp (lsout) information. this information acts as a softclipping stage, so the gain is reduced without any distortion. - the volume control stage adjusts, by 4db step, the loudspeaker amplifier gain, with a maximum depth of 28db. note : in default mode, the gain of the volume control stage is egal to gmax -28db. tea7092 - telephone set integrated circuit 31/57
iii.2 - loudspeaking part supply the loudspeaking part is powered on pin v ls (pin 1). the final stage of the transmit path is simultane- ously used to amplify the transmit signal and to power supply the loudspeaking part. figure 46 shows the loudspeaking part supply. after an off-hook action, during the start-up period and still the microcontroller reset is low, the current power supply of the loudspeaking part is used to charge quickly the capacitor c10 on pin v mc (pin 2), capacitor which is used to power supply the microcontroller. figure 47 shows the line current, i l , partition in the different paths of the tea7092. -i ls : current available for the loudspeaker part and other peripherals. i l (ma) 0 20 40 60 80 100 i ls (ma) i ls i p i vmc 0 20406080100120 0 2 4 6 8 10 10 30 50 70 90 i p /v mc (ma AN848-48.eps figure 47 10 w 400 w itx/41 (see transmit channel) 3 v l i l istart-up switch close, if reset low and il present 12 v mc v ls + c1 + c10 tea7092 AN848-47.eps figure 46 iii - call progress monitor and group listening modes (continued) -i vmc : current for the microcontroller power supply. -i vcc : speech part current consumption. other peripherals like a handsfree circuit or discret cmos logic can be powered on pin v ls (pin 1). tea7092 - telephone set integrated circuit 32/57
ls agc r31 c19 6 lssof v ls vp(lsout) gnd + 0.2 v ls - 0.2 vp(lsout) 4 m a tea7092 AN848-49.eps figure 48 iii - call progress monitor and group listening modes (continued) iii.3 - softclipping stage the softclippingstage avoids distortion on the loud- speaker output lsout (pin 44) over a range of input signals on pin lsin (pin 5). figure 48 shows the loudspeaker softclipping stage. the softclipping stage avoids distortion when there is not enough dc supply voltage on pin v ls (pin 1). this is done by detecting the satu- ration on the pin lsout (pin 44) compared to pin v ls (pin 1) - 0.2v and gnd + 0.2v. when one of these two voltages is reached, the dc voltage on pin lssof (pin 6) increases and the loud- speaker amplifier gain is reduced through the v pp (lsout) signal control. iii.4 - antiacoustic feedback features the same stage is used to control the antiacoustic feedback stage, to avoid howling effect, than to control the squelch stage. figure 49 shows the antiacoustic feedback and squelch stage. in group listening mode, when the handset and the loudspeaker are simultaneously used, it is necces- sary to avoid howling effect between the handset microphone and the loudspeaker. the antiacousticfeedback stage detects the micro- phone signal and, if this one is higher than the fixed threshold (60mv), the gain of the loudspeaker is reduced through ls agc information. by default the loudspeaker amplifier gain reduction is fixed at 15db, this one can be modified through the serial bus interface with the following values : - 10db : code (0111100). - 15db : code (0111101), equivalent to default mode. - 20db : code (01 11110). - 25db : code (01 11111). these different values allow the adaption of the antiacoustic feedback stage to different telephone sets. figure 50 shows the behaviour of the antiacoustic feedback stage (coupled with the squelch feature, if this one is enabled). the signal microphone is amplified by the first stage with a gain close to 200, and filtering on pin asc (pin 18), the cut off frequency is fixed by c25 and the internal 0.5k w . recommended values : c25 = 470nf or 1 m f ? f c = 677hz or 318hz on pin asq (pin 17), the rise and decay times are fixed by r16, c16 and the 10 m a internal current source. - rise time : t r = c16 x 60 x 10 - 3 10 x 10 - 6 , with c16 = 1 m f ? t r = 6ms. - decay time : t d = r16 x c16, with r16 = 330k w andc16 = 1.5 m f ? t d =330ms. tea7092 - telephone set integrated circuit 33/57
normal speech x is programmable through the serial bus (10, 15, 20, 25db) (default value is 15db) low microphone level gmax gmax - 9.5db * 60mv at pin 17 * gls gls - xdb vsl vst vsoft gtx (db) gls is programmable through the volume control stage v mic high microphone signal softclipping mode v mic 9db 3db AN848-51.eps figure 50 iii - call progress monitor and group listening modes (continued) iii.4 - antiacoustic feedback feature (continued) 100k w from microphone preamplifier 0.5k w v cc 10 m a to transmit agc 0.8k w v ref 60mv attenuation programmable from 10 to 25db 17 asq c16 c25 18 asc 60mv ls agc v ref tea7092 25 v ref r16 AN848-50.eps figure 49 tea7092 - telephone set integrated circuit 34/57
iii.5 - maximum output power the loudspeaker part is powered through the pin v ls (pin 1). the v ls power could come from the line, pin v l (pin 3) or an external power supply, +5v for example. when it is powered from the line, pin v l (pin 3), the available current, i ls and the voltage at pin v ls (pin 1) depend on the line current i l . -v ls (pin 1) = v l (pin 3) - (0.95 + 10 x i ls ) -i ls = 0.74 x i l - 1.8ma ; if i l < 15ma -i ls = 0.92 x i l - 4.5ma ; if i l > 15ma the current consumption of the loudspeaker am- plifier is 1ma, so the current available for the loud- speaker is : i ls1 =i ls -1ma figures 51, 52 and 53 give the maximum power available on the loudspeaker for different loud- speaker impedances (25, 32, 50 w ) and different values of r12 (r12 sets up the dc voltage at pin v l (pin 3) and the dc voltage at pin v ls (pin 1), thus it has an influence on the maximum power available on the loudspeaker). i l (ma) (r12 = 82k w ) 0 20 40 60 80 100 p (mw) ls = 25 w ls = 32 w ls = 50 w 110 100 90 80 70 60 50 10 30 50 70 90 40 30 20 10 0 AN848-53.eps figure 52 : output power on lsout i l (ma) (r12 = 110k w ) 0 20 30 40 50 60 p (mw) ls = 25 w ls = 32 w ls = 50 w 110 100 90 80 70 60 50 70 80 90 100 110 40 30 20 10 0 120 130 10 AN848-54.eps figure 53 : output power on lsout iii - call progress monitor and group listening modes (continued) when there is enough line current to drive properly the charge on the loudspeaker output, the maxi- mum peak to peak dynamic is : - on rloudspeaker = 25 w :v pp =v ls - 1.1v - on rloudspeaker = 32 w :v pp =v ls -1v - on rloudspeaker = 50 w :v pp =v ls - 0.9v i l (ma) (r12 = 68k w ) 0 20 40 60 80 100 p (mw) ls = 25 w ls = 32 w ls = 50 w 110 100 90 80 70 60 50 10 30 50 70 90 40 30 20 10 0 AN848-52.eps figure 51 : output power on lsout tea7092 - telephone set integrated circuit 35/57
iii - call progress monitor and group listening modes (continued) sw1 sw2 line interface - ehks interface - pulse dialing interface - rc ring interface reset data clk pon ri tkl ehks microcontroller 1 application tea7092 application v rmc hfin lsin v ls reout 3 2 la lb line keyboard ear ls mic 1 telephone set vspeech v ring recorder +5v microcontroller 2 main power isolation and supplies main answering machine dp hks 4 AN848-55.eps figure 54 iii.6 - external power supply facility the loudspeaker amplifier can be powered through an external power supply, such as a +5v one. this external power supply facility allows the use of tea7092 in a terminal such as an answering machine, a cordless or others, with a direct inter- face with the +5v external power supply. figure 54 shows how to connect the tea7092 in an answering machine. the different inputs/outputs are : - line interface : ? la/lb : line wire terminal - line interface / tea7092 : ? v ring : tea7092 supply in ring mode ? v speech : tea7092 supply in off-hook mode - line interface / microcontoller 1 : ? dp : pulse interface control ? hks : hook switch information ? ehks : on-hookdialing or handsfree information ? tkl : m p line seizure feedback in ehks mode - tea7092 / microcontroller 1 / 2 : ? reset ? pon : line current presence ? ri : ring information ? data / clk : serial bus interface - tea7092 / answering machine : ? 1) outgoing message registration ; the line is open, tea7092 is powered from the +5v and the switch sw1 is closed. ? 2) outgoing message is sent to the line ; tea7092 is powered from the line and the outgoing message is sent on pin hfin (pin 22), amplified through tea7092 and sent to the line. ? 3) incoming message registration ; tea7092 is powered from the line and the incoming message is sent to the answering machine through the intermediate receive output, pin reout (pin 20). ? 4) incoming message playback ; the line is open, tea7092 is powered from the +5v and the incoming message is sent from the answering machine to tea7092 through the pin lsin (pin 5) and amplified in tea7092 loudspeaker amplifier to be heard in the loudspeaker. when tea7092 is powered with +5v on pin v ls (pin 1), the maximum power on the loud- speaker is : -onr ls =25 w : 100mw -onr ls =32 w :80mw -onr ls =50 w :50mw tea7092 - telephone set integrated circuit 36/57
handsfree mode with the last operating code used before ring melody control and configuration codes still stored handset mode with the last operating code used before ring melody control and configuration codes still stored handsfree mode 0110010 or handset mode 0110000 fin code 000xxxx divider n code 1xxxxxx + + fi2 code 000xxxx divider 2 code 1xxxxxx + + fi1 code 000xxxx divider 1 code 1xxxxxx + + ring melody control 0110011 operating codes configuration codes setting handsfree mode handsfree mode 0110010 off-hook off-hook handset mode on-hook or the ring melody is made of n frequencies, the duration of each frequency is determined by the microcontroller - speech - dialing sequence - mutes - error beep - sine wave sequence - agc on or off - sidetone configuration - squelch on or off - decay pon current value - antiacoustic feed back value AN848-56.eps figure 55 : flow chart iii - call progress monitor and group listening modes (continued) iii.7 - ring melody control mode note : for complementary information, see section iv.3 - serial bus interface. in off-hook mode it is possible to control the ring melody using the loudspeaker. the ring melody is audible only in the loud- speaker. this feature is enabled by the serial code : 0110011. tea7092 - telephone set integrated circuit 37/57
fi code 000xxxx divider code 1xxxxxx + + error beep 0011100 beep sent in the earphone off-hook handset mode on-hook speech code 0010000 new beep handset mode no yes off-hook handset mode on-hook volume control 0100xxx group listening code 0110001 group listening mode fi code 000xxxx divider code 1xxxxxx + + error beep 0011100 beep sent in the earphone and in the loudspeaker speech code 0010000 new beep group listening mode no yes AN848-57.eps figure 56 : flow chart iii - call progress monitor and group listening modes (continued) iii.8 - beep error generator note : for complementary information, see sec- tion iv.3 - serial bus interface. in off-hook mode it is possible to send a square wave signal in the earphone and in the loudspeaker by using the ring frequency generator, all frequen- cies available in ring mode are available in beep error mode. this feature is enabled by the serial code : 0 0 1 1 1 0 0 , which sent the square wave in the earphone. to send the beep error on the loudspeaker it is necessary to complete the previous sequence with the group listening code : 0 1 1 0 0 0 1. tea7092 - telephone set integrated circuit 38/57
iv - microcontroller interface iv.1 - microcontroller power supply the microcontroller is used in every modes, speech, dialing and ring. it is requested to start quickly in ring mode, less than 200ms and to maintain the supply on the microcontroller in pulse dialing mode, with a low voltage across the telephoneset, or during an earth loop connection, in these two modes the microcon- troller is supplied through the energy previously stocked in a capacitor and this capacitor should be able to maintain the power on the microcontroller during one second. this compromise between the different modes is carried out through the microcontroller power man- agement which is connectedon pin v mc (pin 2) and on pin v rmc (pin 8). figure 57 shows the microcontroller power supply management. in off-hook mode : - c10 on pin v mc (pin 2) is charged in priority with the istartup (i ls ) currentsource and is, after reset high, powered with i vmc (see section ii.1.3 - start up characteristics). - the voltage on pin v mc (pin 2) is equal to : v l (pin 3) - 0.4v - in pulse dialing mode the microcontroller connected on the 3.5v regulated voltage, pin v rmc (pin 8), is powered through the serial regulator. in ring mode : - for the microcontroller power supply only the capacitor c15 of 4.7 m f connected on pin v rmc (pin 8) has to be charged, so the start- up time in ring mode can be less than 200ms. iv.2 - reset and pon signals these two pieces of information give the status of the pin v rmc (pin 8) and of the line current, i l . in off-hook mode : - pin reset (pin 11) goes at high level when v rmc reaches 2.6v and then remains at high level until v rmc reaches the decay threshold fixed at 2.5v, or the reset code (0 0 1 0 1 1 1) is received through the serial bus interface when pon is at low level. if the reset code has been previously sent pin reset (pin 11) goes back to an high level, if v rmc is higher than the rise threshold, on a rise edge of pon signal. note : when pon is at high level, the reset code is inhibited. - pin pon (pin 12) goes at high level when the voltage at pin v rmc (pin 8) reaches 2.6v and the line current (i l ) reaches the value of 12ma, and then remains at high level until the line current (i l ) goes below the threshold level fixed through the configuration code sent on the serial bus inter- face. ? decay threshold level : i l = 12ma by default configuration. ? decay threshold level : i l = 4ma if the code (0 1 1 1 0 0 1) is sent. i vmc info for pon & reset v bandgap 470k w 8 v rmc c15 4.7 m f + 3 v l 2 v mc + c10 470 m f i start =i ls close if reset low and i l present tea7092 m f + lcd 3.5v 1 v ls battery AN848-58.eps figure 57 tea7092 - telephone set integrated circuit 39/57
i l t v mc 5.6v 2.7v t 2.6v v rmc 3.5v 2.6v 2.5v t pon t d t d t reset t b acdedfda a : on-hook b : start-up + speech c : pulse dialing d : speech or dtmf e : line break exchange duration f : line break exchang duration > td td : delay fixed by the microcontroller reset code (0010111) sent by the microcontroller AN848-59.eps figure 58 iv - microcontroller interface (continued) iv.2 - reset and pon signals (continued) figure 58 shows the reset and pon signals in different modes. different modes : - a : on-hook mode reset and pon stay at low level - b : start up, as soon as the voltage on v rmc reaches the rising threshold and the line current, il is higher than 12ma, reset and pon go at high level. - c : pulse dialing, pon follows the line cur- rent, i l and reset stays at high level. - d : speech or dtmf, reset and pon stay at high level - e : line break exchange duration less than td, as soon as the line current, i l , goes lower than the programmed threshold level (12 or 4ma), the pon signal goes to low level, the microcontroller detects it and starts an internal counter, if the feeding break is less than a prefixed td value (200ms for example), pon goes back to high level with the line current, il and the feedingbreak is ignored by the kit tea7092 and microcontroller. - f : line break exchange duration more than td, as soon as the line current, i l , goes lower than the programmed threshold level (12 or 4ma), the pon signal goes to low level, the microcontroller detects it and starts an internal counter, if the feeding break is more than a prefixed td value (200ms for example), when the counter reaches 200ms is sent the reset code (0 0 1 0 1 1 1) to the tea7092 and the pin reset (pin 11) goes to low level, on this signal the microcontroller goes in reset condition. in ring mode : - pin reset (pin 11) goes at high level when the voltage at pin v rmc (pin 8) reaches the rise threshold and then remains at high level until pin v rmc (pin 8) reaches, when the ring input voltage disappears, the decay threshold. - pin pon (pin 12) stays at low level. tea7092 - telephone set integrated circuit 40/57
a0 a1 a2 a3 a4 a5 a6 t1 t1 t2 t1 t1 t1 > 1 m s;t2>2 m s synchro datas should change during clk = 1 a standard 8-bit code can be sent, the last one is ignored clk pin 13 data pin 14 AN848-60.eps figure 59 iv - microcontroller interface (continued) iv.3 - serial bus interface iv.3.1 - different codes the serial bus interface works with 7 significant bits, a standard 8 bit code can be used, tea7092 only takes care of the seven first bits. figure 59 shows the timing of the pin clk (pin 19) and of the pin data (pin 20). tea7092 initialization after pin reset (pin 11) goes high, tea7092 is initialized, the internal default programmed codes are given in bold in the following code tables. codes programming tea7092 are : - the mode codes : the mode codes are the upper level of codes. codes remarks a6 a5 a4 a3 a2 a1 a0 0110000 handset mode 0110001 group listening mode 0110010 handsfree mode - the operating codes which are related to the mode codes : each operating code can be used under each mode code. when an operating code is sent, the previous one is cancelled. codes remarks a6 a5 a4 a3 a2 a1 a0 0010000 speech 0010001 dialing 0010010muteintransmitand receive paths 0010011 mute in transmit path 0011100 error beep 0011101 sine wave high frequency group 0011110 sine wave low frequency group tea7092 - telephone set integrated circuit 41/57
iv - microcontroller interface (continued) iv.3.1 - different codes (continued) - the flip-flop codes, each time they are sent, tea7092 returns to the previous configura- tion. each flip-flop code is an independent one, its configuration is not modified by any other code, excepted the oinitializationo code and the oreseto code. these codes are accessible through the tele- phone set user, for example : the +6db mode on the earphone which increases the earphone level is accessible through a dedicated key of the telephone set keyboard. codes remarks a6 a5 a4 a3 a2 a1 a0 0010101 v l (3) dc speech / v l (3) dc pulse dialing 0010110 normal receive gain / +6db receive gain 0011010 no transfer / transfer request 0110110 normal transmit gain / -6db transmit gain 0111010 oscillator on / oscillator in stand by mode - the configuration codes, which are gener- ally sent once to program a telephone set at each off-hook action, such as pabx connection or pon threshold level for example. are not acces- sible through the telephone set user. excepted the antiacoustic feedback stage attenuator value and the decay pon current threshold, each code is an independant one, its configuration is not modified by any other code, except for the oinitiali- zationo code and the oreseto code. except for the antiacoustic feedback stage at- tenuator programmation codes and the decay pon current threshold,all the other configuration codes are flip-flop codes. codes remarks a6 a5 a4 a3 a2 a1 a0 0010100 agc on tx & rx paths / no agc on tx & rx paths 0011000 line tracking sidetone network / single sidetone network = 3/4 x zall + 1/4 x zasl 0011011 line tracking sidetone network /single sidetone network = zasl 0011001 squelch feature on / squelch feature inhibited 0 0 1 1 1 1 1 1 0 0 0 0 0 1 decay pon current threshold = 12ma decay pon current threshold = 4ma 0 1 1 1 1 0 0 antiacoustic f eedback stage attenuator = 10db 0111101 antiacoustic feedback stage attenuator = 15db 0 1 1 1 1 1 0 antiacoustic f eedback stage attenuator = 20db 0 1 1 1 1 1 1 antiacoustic f eedback stage attenuator = 25db - the loudspeaker volume control codes. these codes are memorized, independtly from the mode or operating code. for example one of these codes can be sent in handset mode and when the group listening mode code is sent, the loudspeaker output volume will be the one pro- grammed in the handset mode. codes remarks a6 a5 a4 a3 a2 a1 a0 0100111 gmax 0100110 gmax - 4db 0100101 gmax - 8db 0100100 gmax - 12db 0100011 gmax - 16db 0100010 gmax - 20db 0100001 gmax - 24db 0100000 gmax - 28db 0111011 -21db attenuation adder in ring mode* * flip-flop code. tea7092 - telephone set integrated circuit 42/57
iv - microcontroller interface (continued) iv.3.1 - different codes (continued) - hfin input selection for answering machine or cordless connection, it can be requested to select hfin (pin 22) input, without enabling the loudspeaker, for this the following procedure should be sent : ? handsfree code : 0 1 1 0 0 1 0 ? tx & rx mutes : 0 0 1 0 0 1 0 ? hfin input select : 0 1 1 0 1 1 1 to go back to handsfree mode, send : ? speech mode : 0 0 1 0 0 0 0 or to go back to handset mode, send : ? speech mode : 0 0 1 0 0 0 0 ? handset code : 0 1 1 0 0 0 0 - the dtmf and sine wave codes. these codes are memorized, independtly from the mode or operating code. for example one of these code can be sent in handset mode and when the dialing mode code is sent, the dtmf frequencies sent on the line are those previously programmed in the handset mode. codes key in dtmf dialing dtmf dialing (code 0010001 sent before) sine wave (code 0011101 or 0011110 sent before) a6 a5 a4 a3 a2 a1 a0 0000000 o2o 697hz + 1336hz 0000001 o1o 697hz + 1209hz 348hz or 604hz 0000010 oao 697hz + 1633hz 0000011 o3o 697hz + 1477hz 0000100 o8o 852hz + 1336hz 0000101 o7o 852hz + 1209hz 0000110 oco 852hz + 1633hz 0000111 o9o 852hz + 1477hz 426hz or 738hz 0001000 o5o 770hz + 1336hz 385hz or 668hz 0001001 o4o 770hz + 1209hz 0001010 obo 770hz + 1633hz 0001011 o6o 770hz + 1477hz 0001100 o0o 941hz + 1336hz 0001101 o*o 941hz + 1209hz 0001110 odo 941hz + 1633hz 470hz or 816hz 0001111 o#o 941hz + 1477hz - the other codes codes remarks a6 a5 a4 a3 a2 a1 a0 0010001 ring start 0010111 reset control (high to low level on pin 11 (reset)), internal tea7092 initialization and microprocessor serial bus connection inhibited 0110011 ring melody control, to listen the ring melody in the loudspeaker during off-hook mode. 0101000 tea7092 initialization (to go back to internal default programmation) tea7092 - telephone set integrated circuit 43/57
iv - microcontroller interface (continued) iv.3.1 - different codes (continued) - the ring and error beep frequency codes ring frequencies (hz) (see note) fi codes (hz) divider codes n 26321 (000xx10) 23551 (000xx11) 21308 (000xx00) 19455 (000xx01) 1010000 1010001 1010010 1010011 1010100 1010101 1010110 1010111 1011000 1011001 1011010 1011011 1011100 1011101 1011110 1011111 1100000 1100001 1100010 1100011 1100100 1100101 1100110 1100111 1101000 1101001 1101010 1101011 1101100 1101101 1101110 1101111 1110000 1110001 1110010 1110011 1110100 1110101 1110110 1110111 1111000 1111001 1111010 1111011 1111100 1111101 1111110 1111111 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 1645.0 1548.3 1462.3 1385.3 1316.0 1253.4 1196.4 1144.4 1096.7 1052.8 1012.3 974.8 940.0 907.6 877.4 849.1 822.5 797.6 774.1 752.0 731.1 711.4 692.7 674.9 658.0 642.0 626.7 612.1 598.2 584.9 572.2 560.0 548.3 537.2 526.4 516.1 506.2 496.6 487.4 478.6 470.0 461.8 453.8 446.1 438.7 431.5 424.5 417.8 1471.9 1385.3 1308.4 1239.5 1177.5 1121.5 1070.5 1024.0 981.3 942.0 905.8 872.3 841.1 812.1 785.0 759.7 736.0 713.7 692.7 672.9 654.2 636.5 619.8 603.9 588.8 574.4 560.7 547.7 535.2 523.4 512.0 501.1 490.6 480.6 471.0 461.8 452.9 444.4 436.1 428.2 420.5 413.2 406.0 399.2 392.5 386.1 379.8 373.8 1331.7 1253.4 1183.8 1121.5 1065.4 1014.7 968.5 926.4 887.8 852.3 819.5 789.2 761.0 734.8 710.3 687.3 665.9 645.7 626.7 608.8 591.9 575.9 560.7 546.4 532.7 519.7 507.3 495.5 484.3 473.5 463.2 453.4 443.9 434.9 426.2 417.8 409.8 402.0 394.6 387.4 380.5 373.8 367.4 361.1 355.1 349.3 343.7 338.2 1215.9 1144.4 1080.8 1023.9 972.7 926.4 884.3 845.9 810.6 778.2 748.3 720.6 694.8 670.9 648.5 627.6 608.0 589.5 572.2 555.9 540.4 525.8 512.0 498.8 486.4 474.5 463.2 452.4 442.2 432.3 422.9 413.9 405.3 397.0 389.1 381.5 374.1 367.1 360.3 353.7 347.4 341.3 335.4 329.7 324.2 318.9 313.8 308.8 these codes are memorized, independtly from the mode or operating code. for example one of these code can be sent in handset mode and when the error beep code is sent, the square wave frequency sent on the earphone is the one previously programmed in the handset mode. note : it is possible to program n from 1 to 15, 1.0.0.0.0.0.0 to 1.0.0.1.1.1.1, the frequency values are not given in the previous table, but can be calculated in the same way. tea7092 - telephone set integrated circuit 44/57
agc off 0010100 off-hook handset mode on-hook numeric key pressed yes no fi code 000xxxx divider code 1xxxxxx + + key code 000xxxx dialing code 0010001 dtmf sent mute mic & ear 0010010 inter digit pause speech code 0010000 group listening code 0110001 group listening mode volume control 0100xxx up/down no yes error beep 0011100 beep sent in the earphone and in the loudspeaker speech code 0010000 new beep no yes group listening mode handset code 0110000 handset mode +6db on earphone 0010110 normal gain on earphone 0010110 on-hook tea7092 initializated in default mode pon = 1 & reset = 1 configuration code agc inhibited in tx & rx paths dtmf dialing group listening requested filp-flop code earphone level change handset mode requested operating code error beep mode loudspeaker output level adjustment AN848-61.eps figure 60 : flow chart iv - microcontroller interface (continued) iv.3.2 - software example sequence : on-hook ; off-hook ; agc off ; handset ; dtmf dialing ; group listening ; error beep ; +6db on earphone ; normal gain on earphone; on-hook. tea7092 - telephone set integrated circuit 45/57
sw1 1 2 0db or -6db sw2 1 2 to line output amp handset microphone handsfree microphone dtmf generator sinewave generator transmit channel sw3 1 2 0db or -6db dtmf generator sinewave generator receive channel from line earphone sw4 1 2 sw5 1 2 loudspeaker error beep generator ring generator ring melody control generator AN848-62.eps figure 61 iv - microcontroller interface (continued) iv.3.3 - serial bus code actions on switches figure 61, tables below give the switch positions and the generator status for the different serial codes sent on the serial bus interface. the mode codes, handset, group listening act only on switches sw1 and sw5. codes switches generators sw1 sw2 sw3 sw4 sw5 dtmf sinewave error beep ring melody control default 1 1 2 disabled disabled handset mode 0110000 1 2 disabled group listening mode 0110001 1 1 disabled handsfree mode 0110010 2 1 2 1 1 disabled ring melody control 0110011 1 2 2 1 2 enabled the operating codes act only on switches sw2, sw3 and sw4, the positions on the switches sw1 and sw5 are the ones previously determined by the mode codes. note : in ring melody control, the operating codes are not accessible. operating codes switches generators sw2 sw3 sw4 dtmf sinewave error beep speech 0010000 1 1/2* 1 disabled disabled disabled dialing 0010001 2 2 2 enabled disabled disabled mute in tx & rx 0010010 2 2 2 disabled disabled disabled mute in tx 0010011 2 1/2* 1 disabled disabled disabled error beep 0011100 1 2 2 disabled disabled enabled sinewave hf group 0011101 2 2 2 disabled enabled disabled sinewave lf group 0011110 2 2 2 disabled enabled disabled * 1 for handset and group listening modes, 2 for handsfree mode. tea7092 - telephone set integrated circuit 46/57
120 110 100 90 80 70 60 50 40 30 20 10 0 2 4 6 8 10 12 14 16 d i l (ma) i l (ma) AN848-63.eps figure 62 : current line variation to detect transfer iv - microcontroller interface (continued) iv.4 - ring indicator - line current variation indicator the pin ri/vi (pin 10) is used for different modes : - in ring mode, when the threshold level, pro- grammed on pin rsu (pin 40), is reached and the pin reset (pin 11) is high, the pin ri/vi (pin 10) goes to high logic level. - in off-hook mode the pin ri/vi (pin 10) gives an indication of the line current variation when the transfer feature is requested. the transfer feature happens when there are two telephone sets connected in parallel on the same line and the user wants to transfer the communica- tion from telephone o1o to telephone o2o and on- hook telephone o1o. with tea7092 in telephone o1o. telephone o1o is in speech mode, the user presses the otransfero key on telephone o1o. when the otransfero key is pressed, the microcontroller sends the transfert code (0 0 1 1 0 1 0) and tea7092 memorizes the line current value. the user on-hook telephone o1o, the line is main- tained closed by the microcontroller, through the pulse dialing high voltage stage. when the user off-hook telephone o2o, the line current value in telephoneo1o decreases, tea7092 detects this line current variation and the pin ri/vi goes to high logic level. when the microcontroller receives this signal it puts off the high voltage stage of telephone o1o. telephone o1o goes in off-hook mode. figure 62 gives the value of the line current vari- ation ( d i l ) which generates a high logic level on pin ri/vi (pin 10). iv.5 - oscillator the oscillator is powered on pin v rmc (pin 8). the oscillator is only used for dtmf, sine wave, beep error, ring frequency generator and transfer feature. in pulse dialing flash or earth button, it is preferable to reduce, the current consumption on pin v rmc (pin 8) as low as possible, in order to have the lowest possible value of capacitor on pin v mc (pin 2). the toggle code (0 1 1 1 0 1 0) puts the oscillator in stand by mode or not. the current consumption on pin v rmc (pin 8) is : - oscillator on : 250 m a - oscillator off : 50 m a the default condition is oscillator on. if the microcontroller has a 3.58mhz resonator, the oscillator output of the microcontroller can be con- nected, through a capacitor, to the pin osc (pin 9) so as to provide tea7092 with the 3.58mhz signal. iv.6 - microcontroller signal control in the different modes the following table lists the configuration of the signals given by tea7092 in the different modes : signals/modes reset pon ri/ivi on-hook 0 0 0 off-hoo k 1 1 0 ring 1 0 1 line current variation detected in transfer mode 111 external supply only 1 0 0 tea7092 - telephone set integrated circuit 47/57
zb mute 45k w 5k w loudspeaker current source mirror 1/40 v ls c1 + 1 tea7092 from microphone 1k w 9k w 10k w 0db 42 25 21 r8 gtr v ref c14 7 dtmf/sinewave dtmf1 dtmf2 c32 c13 10k w 40k w -1 35 36 3 ear+ ear- v l i l /85 from dc path AN848-64.eps figure 63 dialing code 0010001 key code 000xxxx speech mode numeric key pressed no yes speech code 0010000 numeric key pressed no yes dtmf mode mute 0010010 interdigit pause AN848-65.eps figure 64 v - dialer features v.1 - dtmf dialer the dtmf dialer generates the frequencies in order to drive a telephone set keyboard and complies with the recommandation q.23 of the ccitt-t/cs 46-02. it generates : - the low frequency group (697, 770, 852, 941hz) - the high frequency group (1209, 1336, 1477, 1633hz) figure 63 shows the dtmf amplifier path. the mute signal driven through the serial bus, selects the microphone signal or the dtmf signal and the confidence tone level for the earphone and the loudspeaker. the dtmf level is fixed by c13 on pin dtmf1 (pin 7) and by r8 on pin gtr (pin 21), c32 on pin dtmf2 (pin 42) fixes the cut off fre- quency of the second filter. - cut-off frequency on dtmf1 : f 1 = 1 2 ? p ? 20 ? 10 3 ? c13 with c13 = 47nf, f1 = 170hz. an internal twist between each dtmf frequency is programmed so as to take care to follow the t/cs46-02 recommended levels. - cut-off frequency on dtmf2 : f 2 = 1 2 ? p ? 10 ? 10 3 ? c32 with c32 = 2.7nf, f2 = 5.9khz. figure 64 shows the dtmf signaling. tea7092 - telephone set integrated circuit 48/57
t t v set (v) 0 5v max. 0 v l (v) 2 code (0 010101) sent pulse dialingmode other modes flash other modes dp ( m p output) AN848-66.eps figure 65 : mask / no mask mode v - dialer features (continued) v.2 - sinewave generator the sinewave generator is programmable like the dtmf generator. this one generates the dtmf frequencies divided by 2, in single tone mode in two groups : - codedtmf + code 0011101: 348,385,426, 470hz - codedtmf + code 0011110: 604,668, 738, 816hz the sinewave level on line is 8db lower than the dtmf dialing level. this sinewave generator can be used in mute mode to send on line a signal to advise the other party than you are in secret mode. v.3 - pulse dialer interface in pulse dialing mode, if the code (0 0 1 0 1 0 1) is used, the voltage across tea7092 is reduced to 2v on pin v l (pin 3), this way it is possible to achieve a low voltage across the telephone set during the make period of the pulse dialing sequence. figure 65 shows the dc voltage across tea7092 and across the telephone set in pulse dialing mode. note : it is possible to generatean acoustic control in the earphone in pulse dialing mode with the code (0010101). this code should be sent twice within the break period of the pulse dialing. for ex- ample, if the break period is 60ms, send the code (0010101) 10ms after the start of the break period and send it again 10ms before the end of the break period. this will generate a dc level change in the earphone which will be audible. tea7092 - telephone set integrated circuit 49/57
r37 r35 + c6 d2 r38 c30 i(v zp ) r32 r36 v ring d3 r33 d7 t1 t2 l1 + c1 38 40 1 rsu v ls v zp 11.2v 24v 5.6v 150k w 2.6v 150k w 26khz logic control i vzp info 1.2v logic control ri v ls > 2.6v v rmc > 2.6v serial regulator 8 vrmc + c15 135k w 90k w 100 m a i/17.5k w 40k w ri 6 lssof r31 c19 ls amp (v ls - vlsout) < 0.2v 44 lsout + c2 fi ring v in i a = f{(i vzp )} 41 rco r40 c4 gain = 16 tea7092 39 swp AN848-67.eps figure 66 vi - ringer features vi.1 - ringer power supply in ring mode only the ring part, the loudspeaker amplifier, the logic part and the microcontroller supply are powered. the supply is provided by a switch mode power supply. figure 66 shows the ring part. the switch mode power supply converts the high ac ring line voltage, 30 to 90v rms at 25 or 50hz, into a low dc voltage, 3 to 5.6v, which is used to supply the loudspeaker amplifier and the microcon- troller. the switch mode power supply made by t1, t2, l1, d7 and the resistors associated, is driven through the pin swp (pin 39). the control on swp is done by a 26khz oscillator. the coil l1 is 1mh, the diode d7 is a 1n4148. vi.2 - start-up threshold level by default, the ring threshold level is internally set up at 18.8vdc on pin rsu (pin 40) : (3 x 5.6v + v be (0.6v) + 2 x v thn (2 x 0.7v)), equivalent to an ac ring level of 13.3v rms . as soon as this threshold level is reached, is a 11.2v hysteresis is introduced to assurethe system's stability the v ring1 start up level is set up on pin rsu (pin 40) with r35 and if neccessary a zener diode d5 added in serial with r35, most of the countries don't request d5. v ring1 : start up level. v ring1 = 18.8 + ? ? ? r35 300k w ? 0.7 ? ? ? + v z ( d5 ) in v note : recommended value for r35 is 56k w . tea7092 - telephone set integrated circuit 50/57
i e0 rl1 l1 i e is rl i s0 v ls i srl c1 d7 v e1 c5 i et v e sw1 AN848-68.eps figure 67 vi - ringer features (continued) vi.3 - ring frequency generator the ring frequency values which can be generated are those given page 45 of this application note. on the table given at page 45, only the frequency values for n > 15 are given, the frequency values from n = 1 (1000000)to n = 15 (1001111) are also accessible, if it is neccessary to generate a fre- quency higher than 1645hz. vi.4 - output power optimization the power available on pin lsout (pin 44) de- pends on : - the country requires : ? minimum input ac level in test conditions. ? ring impedance. taking in account these main requests the power on pin lsout (pin 44) is optimized through the resistor r40 connected on pin rco (pin 41). - the yield of the switch mode power supply. the principal parameters which influence the yield are : ? d7 v be value. ? t1 v cesat and base current values (the maxi- mum i c peak value is 100ma). ? l1 serial resistor value. ? current consumption on pin v zp (pin 38) and on pin rsu (pin 40). ? bias current consumption on pin v ls this paragraph gives information on : - the switch mode power supply concept. - the switch mode power supply yield. - the ring output power optimization on pin lsout (pin 44). vi.4.1 - switch mode power supply concept after the ring bridge, the switch mode power supply concept is represented in figure 67. v e input voltage equivalent to v ring1 v e1 input voltage after the switch sw1 i e mean input current v s output voltage at pin v ls (pin 1) i s mean output current v d voltage across d7 when it is in forward mode i e0 primary bias current i s0 secondarybias current rl1 resistive part of the coil l1 switch sw1 - v cesat of t1 pnp -i b1 , t1 base current -t d , t1 desaturation time -v e1 =v e -v cesat(t1) figure 68 gives the voltage,v e1 , the current in the coil, i self , the current in d7, i diode and the current in the switch sw1 given by c6, i capa . the value of the maximum current in the coil is fixed by t on and t off depends on rl. when rl de- creases, t on increases. the coil value should be calculated so that the current in the coil reaches the zero value with the minimum charge. i max. = t on ? v e1 - v ls l (1) l is the value of the coil l1. the ratio between t on and t off is : t on t off = v d + v ls v e1 - v ls (2) the output current i s is : i s = i max. 2 ? t on + t off t (3) tea7092 - telephone set integrated circuit 51/57
t t t i diode i capa i coil t -v d v s v e1 t on t off t = 38.46 m s t is internally fixed by the 26khz oscillator AN848-69eps figure 68 vi - ringer features (continued) vi.4 - output power optimization (continued) vi.4.2 - switch mode power supply losses the sum of all the different losses gives the yield of the switch mode power supply. the final yield is : h final = pout pout +s pi where : pi are the different losses, pout is the power in the load rl : pout = 4 x rl x (i srl ) 2 . the output current i s is : i s =i srl +i s0 . using the equations (1), (2) and (3), the values of t on and t off can be found : t on t = ````````````` ` 2 ? l ? f ? i s ? v ls + v d ( v e1 - v ls ) ? ( v e1 + v d ) f = 26khz t off t = ````````````` 2 ? l ? f ? i s ? v e1 - v ls ( v ls + v d ) ? ( v e1 + v d ) i max. = ```````````` ` 2 l ? f ? i s ? ( v e1 - v ls ) ? ( v ls + v d ) v e1 + v d tea7092 - telephone set integrated circuit 52/57
vi - ringer features (continued) vi.4 - output power optimization (continued) the different losses are : - in the switch sw1 : ? v cesat :p vcesat = i max. ? t on 2 ? t ? v cesat = i s ? v cesat ? v ls + v d v e1 + v d ? t1 base current (i bt1 ): p ibt1 = v e ? i bt1 ? t on t = v e ? ib t1 ? ````````` ` 2 ? l ? f ? ( v ls + v d ) ( v e1 - v ls ) ? ( v e1 + v d ) ? t d , desaturationtime of t1 : p desat = v e ? i max. ? t d 25 ? t ? = v e ? t d ? ``````````` 2 ? f ? i s ? ( v e1 - v ls ) ? ( v ls + v d ) l ? ( v e1 + v d ) ? t2 base current (ibt2) : p ibt2 = ( v e - 8.2 ) 2 r32 - in the diode d7 : p diode = i max. ? t off 2 ? t ? v d ? = i s ? v d ? v e1 - v s v e1 + v d - at the primary ; the sum of these losses is equal to : v e xi e0 ? on pin v zp (pin 38) : v zp (pin 38) = 2.55v ; p vzp = ( v e - 2.55 ) 2 r34 + r37 ? on pin rsu (pin 40) : p rsu = ( v e - 5.6 ) r35 + 300k w ? v e - in the coil : p coil = r coil ? ? ? ? i max. 2 ? ? ? 2 ? t on 2 + t off 2 t 2 ? = r coil ? i s 2 ? ( v e1 - v ls ) 2 + ( v ls + v d ) 2 ( v e1 + v d ) 2 - at the secondary ; the sum of these losses is equal to : v ls xi s0 ? current consumption of all the part powered on pin v ls (pin 1) : p vls =v ls xi pls . ? current consumption of the microcontroller : p m p =v ls xi m p ;i s0 =i pls +i m p . ? v cesat of the loudspeakeramplifier output stage : p ols = 0.2 x i srl - the sum of the losses is : p total = s p i =pv cesat +p ibt1 +p desat +p ibt2 +p vzp +p rsu +p coil +p vls +p m p +p ols +p diode vi.4.3 - output power adjustment the optimization of the ouput power depends on the system environment. it is therefore neccessary to know the power which can be given by the system in the best and worst loop line. each country has a different loop line system. figure 69 shows the system configuration. the minimum power available, pe1 is for : v rgene(min.) and rl(max). the maximum power available, pe2 is for : v rgene(max.) and rl(min). figure 70 gives the power available at the input of the switch mode power supply. the output signal on pin lsout (pin 44) is con- trolled through the current information given on pin v zp (pin 38) (see figure 66). cr v e pe ring rc network fixed by the country requirement v rgene (20 to 60hz) rl telephone set AN848-70.eps figure 69 v e (v) pe (mw) pe2 pe1 v e2 v e1 v rgene (max.) rl (min.) v rgene (min.) rl (max.) AN848-71.eps figure 70 tea7092 - telephone set integrated circuit 53/57
v ring (v) 0 2 4 6 8 u (v) rco (pin 41) v pp (lsout) v ls (pin 1) 0 1020304050 1 3 5 7 no working area AN848-72.eps figure 71 vi - ringer features (continued) vi.4 - output power optimization (continued) the principle is : - from the current i(v zp ) in the resistor r37, a current ia is issued and equal to : i a = i ( v zp ) - 39 m a - 2.6 r38 9 (1) the 39 m a current is the bias current of the internal 2.6v zener connected on pin v zp (pin 38). i ( v zp ) = v ring - 2.6 r37 (2) - the current ia generates a voltage on pin rco (pin 41) equal to : v(rco) = r40 x ia (3) - this input voltage, mixed with the ring frequency is amplified to the loudspeaker connected on pin lsout (pin 44), and the peak to peak square output voltage v pp (lsout) is : v pp (lsout) = 16 x v(rco) (4) (1), (2), (3) & (4) ? v pp ( lsout )= 16 9 ? r40 ? ? ? ? v ring r37 - 39 m a - 2.6 r35 // r38 ? ? ? when the v ring input voltage is high enough to saturate the output stage on pin lsout (pin 44), compared to pin v ls (pin 1), (v ls (pin 1) - v pp (lsout) < 0.2v), the switch in serial with the current source on pin lssof (pin 6) is activated, and the input voltage on pin lssof (pin 6) is converted in current, with a 1/17.5k w transconductance. finally this current increases the voltage on pin v ls (pin 1) and al- lows the output voltage, v pp(lsout) on pin lsout (pin 44) to increase. at low v ring input voltage, pin v ls (pin 1) is clamped at a 3v minimum voltage, to maintain a proper supply to the microcontroller on pin v rmc (pin 8), and the output voltage on pin lsout(pin 44) is progressively reduced. when the v ring input voltage increases, the pin v ls (pin 1) increases up to 6v and is clamped to 6v by an internal zener. the figure 71 gives the voltage on pin v ls (pin 1), on pin rco (pin 41) and the v pp(lsout) on pin lsout (pin 44) versus the v ring input voltage with : r37 = 200k w , r38 = 150k w , r40 = 47k w the values of r37, r38 and r40 should be calcu- late to adapt the output power requested on pin lsout (pin 44) to the available power, during ring mode, on the terminal wire as described on figures 69 and 70 of this application note. the recommended values for a ring network of, c ring =1 m f, r ring = 1.5k w are : - r37 = 200k w , r38 = 150k w - p40 = 47k w , if f ring = 25 or 50hz / r loudspeaker =50 w - r40 = 39k w ,iff ring = 50hz / r loudspeaker =32 w - r40 = 33k w ,iff ring = 25hz / r loudspeaker =32 w vi.5 - microcontroller management (ri / reset) in ring mode, two pieces of information are given to control the microcontroller : - pin reset (pin 11) which goes at level o1o if pin v rmc (pin 8) > 2.6v. - pin ri/vi (pin 10) which goes at level o1o if : ? pin rsu (pin 40) > 19v ? pin v rmc (pin 8) > 2.6v ? current in pin v zp (pin 38) > 40 m a - after a ring mode, pin ri/vi (pin 10) goes back to level o0o, if pin rsu (pin 40) goes lower than 8v. tea7092 - telephone set integrated circuit 54/57
vi - ringer features (continued) vi.6 - ring software to generate the ring on the loudspeaker, the flowchart is in figure 72. on-hook ri = 1 yes no ring start 0010001 group listening code 0110001 fi1 code 000xxxx volume change no yes init code 0101000 default : gmax -28db (0 100000) ring mode volume control code 0100xxxor0111011 divider 1 code 1xxxxxx + + fi2 code 000xxxx divider 2 code 1xxxxxx + + fin code 000xxxx divider n code 1xxxxxx + + ri = 1 no yes pon = 1 yes no off-hook with default conditions on-hook steady state AN848-73.eps figure 72 tea7092 - telephone set integrated circuit 55/57
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 41 42 40 43 44 mic1 mic2 v ref vcc tsoft softl i ref v s slpe agnd i ll reset ri/vi osc v rmc dtmf1 lssof lsin v refl v l v mc v ls i sl ear- grec ear+ v zp swp rsu rco dtmf2 gnd lsout hfin reout recin gtr asc asq snll snsl data clk pon r18 r3 r2 r1 + c11 r19 r12 r4 c3 r37 r35 r38 c30 r40 c4 r36 t1 t2 r23 r32 d3 d2 c6 + d7 c32 + c2 l1 tea7092 r17 c17 r14 + c24 + c1 c20 r31 c19 c13 3.58mhz agnd c26 w1 r21 c31 r8 r15 c14 agnd c25 c27 c12 r16 c16 r13 r5 r6 c5 r27 r28 r29 c28 r11b r11a r10 r9 c8 agnd c9 v l1 cr1 d1 agnd ear- ear+ mic- mic+ hfin reout ring1 gnd + c10 v ref + c15 v mc v rmc agnd v ls ls1 lsin ri/vi reset pon clk data ring ls ampliflier v ref return loss sidetone rx gain AN848-74.eps vii - application diagram ref. part ref. part ref. part ref. part ref. part r1 56k w r15 2.2k w r36 4.7k w l1 1mh c14 47nf r2 30k w r16 330k w r37 200k w q1 3,58mhz c15 4.7 m f r3 2.7k w r17 75k w r38 150k w c1 100 m f c16 1 m f r4 820k w r18 18k w r40 47k w (50hz/50 w )* c2 47 m f c17 330pf r5 0 r19 6.8k w 47k w (25hz/50 w )* c3 150nf c19 470nf r6 39k w r21 1.5k w 39k w (50hz/32 w )* c4 220nf c20 47nf r8 1.62k w r27 3.3k w 33k w (25hz/32 w )* c5 560pf c25 470nf r10 680 w r28 33k w d1 13v c6 10 m f (63v) c26 47nf r11a 24 w r29 18k w d2 47v c8 47 m f c27 100nf r11b 6.2 w r31 560k w d3 8.2v c10 470 m f c28 1.8nf r12 100k w r32 220k w d7 1n4148 c11 1 m f c30 1.2nf r13 2.7k w r33 1.5k w t1 bc556b c12 100nf c31 10nf r14 47k w r35 56k w t2 bc546b c13 47nf c32 2.7nf cr1 10nf * (ring frequency / ls impedance) tea7092 - telephone set integrated circuit 56/57
information furnished is believed to be accurate and reliable. however, sgs-thomson microelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. no licence is granted by implication or otherwise under any patent or patent rights of sgs-thomson microelectronics. specifications mentioned in this publication are subject to change without noti ce. this publication supersedes and replaces all information previously supplied. sgs-thomson microelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of sgs-thomson microelectronics. ? 1996 sgs-thomson microelectronics - all rights reserved purchase of i 2 c components of sgs-thomson microelectronics, conveys a license under the philips i 2 c patent. rights to use these components in a i 2 c system, is granted provided that the system confo rms to the i 2 c standard specifications as defined by philips. sgs-thomson microelectronics group of companies australia - brazil - canada - china - france - germany - hong kong - italy - japan - korea - malaysia - malta - morocco the netherlands - singapore - spain - sweden - switzerland - taiwan - thailand - united kingdom - u.s.a. tea7092 - telephone set integrated circuit 57/57

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