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order this document by MC33219A/d device operating temperature range package semiconductor technical data dw suffix plastic package case 751e voice switched speakerphone circuit pin connections ordering information MC33219Adw MC33219Ap t a = 40 to +85 c soic plastic dip 24 1 p suffix plastic package case 724 24 1 cp2 1 24 (top view) v cc 2 3 4 5 6 7 8 9 10 11 12 23 22 21 20 19 18 17 16 15 14 13 xdi cpt tli tlo v b c t cd nc cpr rli rlo tao tai mco mci vlc mute rxi rxo rai rao gnd simplified block diagram this device contains 384 active transistors. microphone transmit out mute vol cont v b v b v b v b v b bnm reg. r x attenuator MC33219A v cc t x attenuator attenuator control dtd speaker amplifier speaker cd receive in bnm 1 motorola analog ic device data
the m otorola m c33219 a v oic e s witche d s peakerphon e c ircuit incorporates the necessary amplifiers, attenuators, level detectors, and control a lgorith m t o f or m t h e h ear t o f a h ig h q ualit y h andsfree speakerphone system. included are a microphone amplifier with mute, transmit and receive attenuators, a background monitoring system for both the transmit and receive paths, and level detectors for each path. an agc system reduces the receive gain on long lines where loop current and power are in short supply . a dial tone detector prevents fading of dial tone. a chip disable pin permits conserving power when the circuit is not in use. the volume control can be implemented with a potentiometer. the MC33219A can be operated from a power supply , or from the telephone line, requiring typically 3.2 ma. it can be used in conjunction with a variety of speech networks. applications include not only speakerphones, but intercoms and other voice switched devices. the MC33219A is available in a 24 pin narrow body dip , and a wide body soic package. ? supply voltage range: 2.7 to 6.5 v ? attenuator range: 53 db ? background noise monitor for each path ? 2 point signal sensing ? volume control range: typically 40 db ? microphone and receive amplifiers pinned out for flexibility ? microphone amplifier can be muted ? mute and chip disable are logic level inputs ? chip deselect pin powers down the entire ic ? ambient operating temperature: 40 to + 85 c ? 24 pin narrow body (300 mil) dip and 24 pin soic ? motorola, inc. 1995
MC33219A 2 motorola analog ic device data maximum ratings rating symbol min max unit supply voltage v cc 0.5 7.0 vdc any input v in 0.4 v cc + 0.4 vdc maximum junction temperature t j +150 c storage temperature range t stg 65 +150 c note: devices should not be operated at or outside these values. the arecommended operating conditionso provide for actual device operation. recommended operating conditions characteristic symbol min typ max unit supply voltage (nonagc range) v cc 3.5 6.5 vdc (agc range) 2.7 3.5 maximum attenuator input signal v in(max) 300 mvrms volume control input (pin 19) v invlc v b 1.1 v b vdc logic input voltage (pins 8, 18) v inl vdc low 0 0.8 high 2.0 v cc operating temperature range t a 40 85 c v b output current (v cc = 5.0 v) i vb see figure 12 ma electrical characteristics (t a = 25 c, v cc = 5.0 v, cd 0.8 v, unless noted. see figure 2.) characteristic symbol min typ max unit power supply supply current (enabled, cd 0.8, v b open) i cce ma idle mode 2.0 3.2 5.0 t x mode 4.2 r x mode 4.0 supply current (disabled, cd = 2.0 v, v b open) i ccd m a v cc = 3.0 v 65 v cc = 5.0 v 50 110 170 v cc = 6.5 v 145 v b output voltage (i vb = 0, cd = 0) v b vdc v cc = 2.7 v 0.9 v cc = 5.0 v 2.1 2.2 2.3 v cc = 6.5 v 3.0 v b output resistance (i vb 1.0 ma) r ovb 600 w psrr @ v b versus v cc , f = 1.0 khz, c vb = 100 m f psrr 57 db attenuator control c t voltage (with respect to v b ) v ct v b mv r x mode (vlc = v b ) 150 idle mode 0 t x mode 100 c t source current (switching to r x mode) i ctr 110 90 70 m a c t sink current (switching to t x mode) i ctt 35 50 65 m a c t idle current i cti 3.0 0 3.0 m a dial tone detector threshold (with respect to v b at rai) v dt 40 20 8.0 mv vlc input current @ i vlc m a vlc = v b 0 vlc = v b 1.0 v 8.0 6.0 3.0 vlc input resistance r vlc 167 k w
MC33219A 3 motorola analog ic device data electrical characteristics (t a = 25 c, v cc = 5.0 v, cd 0.8 v, unless noted. see figure 2.) characteristic symbol min typ max unit attenuators receive attenuator gain (f = 1.0 khz) db full volume r x mode g rx 3.0 6.7 9.0 t x mode g rxt 49 46 43 idle mode g rxi 28 25 22 range (r x to t x mode) d g rx 50 53 56 volume control range (r x mode only, vlc varied from v b to (v b 1.0 v)) v cr 34 40 46 db agc attenuation range (v cc = 3.5 to 2.7 v, receive mode only, vlc = v b ) g agc 20 26 36 db transmit attenuator gain (f = 1.0 khz) db t x mode g tx 3.0 6.7 9.0 r x mode g txr 49 46 43 idle mode g txi 19 16 13 range (t x to r x mode) d g tx 50 53 56 rao, tao output current capability v cc 3.0 v v cc < 3.0 v i oatt 2.5 0.7 ma peak rao offset voltage with respect to v b v rao mvdc r x mode 120 idle mode 0 t x mode 10 tao offset voltage with respect to v b v tao mvdc r x mode 0 idle mode 8.0 t x mode 70 rai, tai input impedance (v in < 300 mvrms) r inatt 100 k w rai, tai input offset voltage with respect to v b v inatt 0 mvdc microphone amplifier (pins 20, 21) output offset with respect to v b (rf = 300 k w ) mco vos 9.0 mvdc input bias current (pin 20) i mbias 30 na open loop gain (f < 100 hz) v volm 70 db gain bandwidth gbw m 1.5 mhz maximum output voltage swing (1% thd) v omax 4.1 vpp maximum output current capability i omco 2.0 ma peak muting ( d gain) rf = 300 k w rf = 100 k w gmt 70 78 68 db receive amplifier (pins 16, 17) output offset with respect to v b (rf = 10 k w ) rxo vos 1.0 mvdc input bias current (pin 17) i rbias 30 na open loop gain (f < 100 hz) a volr 70 db gain bandwidth g bwr 1.5 mhz maximum output voltage swing (1% thd) v omax 4.1 vpp maximum output current capability i orxo 2.0 ma peak
MC33219A 4 motorola analog ic device data electrical characteristics (t a = 25 c, v cc = 5.0 v, cd 0.8 v, unless noted. see figure 2) characteristic symbol min typ max unit level detectors and background noise monitors t x r x switching threshold (pins 4, 11) i th 0.8 1.0 1.2 m a cpr, cpt output resistance (for pulldown) r cp 5.0 w cpr, cpt leakage current i cplk 0.2 m a cpr, cpt nominal dc voltage (no signal) v cp 1.9 vdc tlo, rlo, cp2 source current (@ v b 1.0 v) i ldoh 2.0 ma tlo, rlo, cp2 output resistance r ld 500 w tlo, rlo, cp2 sink current (@ v b + 1.0 v) i ldol 2.0 m a mute input (pin 18) switching threshold (see text) v thmt 1.01.4 vdc input resistance (v in = 0.85 v) r mt 70 115 160 k w input current (v in = 5.0 v) i mt 75 m a timing to mute to enable t mt t enm 1.5 5.0 m s cd input (pin 8) switching threshold v thcd 1.5 vdc input resistance (v in = 0.8 v) r cd 150 235 350 k w input current (v in = 5.0 v) i cd 40 m a timing to disable to enable t cd t enc 5.0 see figure 22 m s system distortion (see figure 1) microphone amplifier + t x attenuator distortion thd t 0.05 3.0 % receive amplifier + r x attenuator distortion thd r 0.05 3.0 % typical temperature performance characteristic 40 c 0 c 25 c 85 c unit power supply current enabled, v b open disabled, v b open 3.18 131 3.23 119 3.23 110 3.12 121 ma m a v b output voltage (i vb = 0) 2.09 2.17 2.22 2.31 vdc ct source current switching to r x mode 80 87 90 90 m a ct sink current switching to t x mode 43 47 50 51 m a attenuator aono gain 6.9 6.8 6.7 6.6 db attenuator range 53 53 53 53 db volume control range (r x mode only, v lc varied from v b to (v b 1.0 v)) 36 39 40 41 db agc attenuation range 32 24 26 30 db temperature data is typical performance only , based on sample characterization, and does not provide guaranteed limits over temperature.
MC33219A 5 motorola analog ic device data figure 1. system distortion test v out v in 3.5 mv 1.0 khz v b t x attenuator 23 tao tai 22 21 20 mci mco 3.0 k 300 k note: r x attenuator forced to receive mode. note: t x attenuator forced to transmit mode. v out v in 350 mv 1.0 khz v b r x attenuator 14 rao rai 15 16 17 rxi rxo 10 k 10 k
MC33219A 6 motorola analog ic device data pin function description pin symbol description 1 cp2 a capacitor at this pin stores voltage representing the transmit background noise and speech levels for the background noise monitor. 2 xdi input to the transmit background noise monitor. 3 cpt an rc sets the time constant for the transmit background noise monitor. 4 tli input to the transmit level detector. 5 tlo output of the transmit level detector. 6 v b a midsupply reference voltage, and analog ground for the amplifiers. this must be well bypassed for proper power supply rejection. 7 c t an rc sets the switching time between transmit, receive and idle modes. 8 cd chip disable (logic input). when low, the ic is active. when high, the entire ic is powered down and nonfunctional, except for v b . input impedance is nominally 125 k w . 9 nc no internal connection. 10 cpr an rc sets the time constant for the receive background noise monitor. 11 rli input to the receive level detector. 12 rlo output of the receive level detector. 13 gnd ground pin for the entire ic. 14 rao output of the receive attenuator. 15 rai input to the receive attenuator and the dial tone detector. input impedance is nominally 100 k w . 16 rxo output of the receive amplifier. 17 rxi inverting input of the receive amplifier. bias current flows out of the pin. 18 mute mute input (logic input). a logic low sets normal operation. a logic high mutes the microphone amplifier only. input impedance is nominally 67 k w . 19 vlc volume control. when vlc = v b , maximum receive gain is set when in the receive mode. when vlc = v b 1.0 v, receive gain is down 40 db. no effect in the transmit or idle mode. current flow is out of the pin. input impedance is nominally 167 k w . 20 mci inverting input of the microphone amplifier. bias current flows out of the pin. 21 mco output of the microphone amplifier. 22 tai input of the transmit attenuator. input impedance is nominally 100 k w . 23 tao output of the transmit attenuator. 24 v cc power supply pin. operating range is 2.7 v to 6.5 vdc. bypassing is required.
MC33219A 7 motorola analog ic device data cpr figure 2. MC33219A block diagram and test circuit notes: 1. all capacitors are in m f unless otherwise noted. 2. v alues shown are suggested initial values only . see applications information for circuit adjustments. mc34119 speaker amplifier receive input from 24 wire converter r x attenuator attenuator control circuit t x attenuator bias agc t x bnm dial tone detector r x bnm 0.1 5.1 k r 2 10 k 10 k 0.1 1.0 47 100 k v cc 100 15 15 k 1.0 100 v b v b v th 0.1 volume control (see figure 28) v b normal normal mute mute disable vlc cd gnd v cc 0.47 from microphone transmit output to 24 wire converter 47 0.1 4.7 k 0.1 5.1 k 300 k 1.0 100 k v cc v b c t tlo rxi 6 7 5 17 16 rxo 15 rai 14 rao 11 rli 12 rlo 10 13 24 8 19 18 20 22 21 tai mco 3.0 k v b 3 cpt 4 tli 2 xdi 23 tao 1 cp2 t x r x comp. MC33219A v b v b v cc v b mci r 1
MC33219A 8 motorola analog ic device data 1.4 10 100 10 vlc voltage, with respect to v b (v) attenuator gain (db) figure 3. attenuator gain versus v ct (pin 7) v ct v b (mv) figure 4. receive attenuator versus volume control receive attenuator gain (db) 0 50 50 150 100 1.2 0.8 1.0 0 0.6 0 10 20 30 40 0 10 20 30 40 50 50 transmit attenuator receive attenuator circuit in receive mode 0.4 0.2 v cc 3.5 v v cc = 3.3 v v cc 2.9 v 2.0 m a v out 1.0 m f 500 tli rli xdi tlo rlo cp2 i in figure 5. receive gain versus v cc 0 200 2.7 10 v out b , output vol tage (mv) figure 6. level detector dc transfer characteristics 2.9 3.1 3.5 3.3 10 20 30 50 40 100 50 100 150 receive attenuator gain (db) i in , dc input current ( m a) 40 80 120 160 200 v v cc (v) circuit in receive mode 0 0 50 v out b , output vol tage (mv) v 100 100 0 100 f, frequency (hz) v in , input signal (mvrms) figure 7. level detector ac transfer characteristics figure 8. level detector ac transfer characteristics versus frequency 300 1.0 k 10 k 20 20 60 0 60 20 0 60 20 100 r = 5.1 k, c = 0.1 m f 2.0 m a v out 1.0 m f 500 tli rli xdi tlo rlo cp2 v in @ 1.0 khz 40 80 120 160 200 c r v in = 100 mvrms 2.0 m a v out 1.0 m f 500 tli rli xdi tlo rlo cp2 v in c 5.1 k 0.1 m f r = 10 k, c = 0.047 m f r = 10 k, c = 0.1 m f v out b , output vol tage (mv) v
MC33219A 9 motorola analog ic device data input current ( a) m input voltage (v) 120 0 60 input current ( a) m figure 9. cd input characteristics (pin 8) input voltage (v) figure 10. mute input characteristics (pin 18) 40 20 0 80 40 0 1.0 2.0 3.0 4.0 5.0 6.0 0 1.0 2.0 3.0 5.0 7.0 4.0 valid for v in v cc 7.0 6.0 valid for v in v cc v b (v) 0 4.0 0 6.0 i b , output current (ma) i cc (ma) v cc (v) figure 11. power supply current figure 12. v b output characteristics 3.0 2.0 1.0 5.0 3.0 2.0 0 0.5 1.0 1.5 1.0 2.0 3.0 4.0 5.0 6.5 1.0 0 4.0 v cc = 5.0 v v cc = 6.5 v v cc = 3.0 v cd 0.8 v idle mode cd 2.0 v 145 m a 2.0 v cc = 4.0 v 2.5 6.0 200 100 v cc (v) psrr (db) f, frequency (hz) figure 13. v b power supply rejection versus frequency and v b capacitor figure 14. receive amp and microphone amp output swing 80 60 20 0 4.0 2.0 0 1.0 k 10 k 20 k 3.5 4.5 5.5 6.5 pp output swing (v) 40 c vb = 1000 m f c vb = 33 m f c vb = 100 m f thd 1.0% thd = 5.0 %
MC33219A 10 motorola analog ic device data input current ( a) m 1.4 0 1.0 k 100 vlc voltage, with respect to v b (v) d gain, muting (db) figure 15. microphone amplifier muting versus feedback resistor rf, feedback resistor ( w ) figure 16. vlc input current (pin 19) 80 60 40 20 0 2.0 4.0 6.0 8.0 10 10 k 100 k 300 k 1.2 1.0 0.8 0 0.6 2.7 v v cc 6.5 v 2.7 v v cc 6.5 v 0.4 0.2 figure 17. idle transmit timing note: refer to figure 2 for component values. t iming and output amplitudes shown are nominal, and are for the indicated input signal and component values. actual timing and outputs will vary with the application. ????????????? ????????????? ????????????? ????????????? ???? ???? ???? ???? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ???? ???? ???? ???? ???? ???? ???? ????????????? ????????????? ????????????? ????????????? ????????????? ????????????? ????????????? tai input cpt c t tlo tao output 30 ms 360 ms 36 mv 100 mv 120 mv 170 mv 270 mv 85 ms 420 mvrms 37 mvrms 5.0 mvrms 1.0 s 200 mvrms, 1.0 khz idle 225 ms time constant t x
MC33219A 11 motorola analog ic device data ????????????? ????????????? ????????????? ????????????? ????????????? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ????????????? ????????????? ????????????? ????????????? ????????????? ????????????? figure 18. idle receive timing note: refer to figure 2 for component values. t iming and output amplitudes shown are nominal, and are for the indicated input signal and component values. actual timing and outputs will vary with the application. rai input cpr c t rlo rao output 30 ms 450 ms 100 mv 270 mv 85 ms 420 mvrms 5.0 mvrms 1.0 s 200 mvrms, 1.0 khz r x idle 225 ms time constant 150 mv
MC33219A 12 motorola analog ic device data 72 ms ?????????? ?????????? ?????????? ?????????? ????????? ????????? ????????? ????????? ?????????? ?????????? ?????????? ?????????? ??? ??? ??? ??? ??? ??? ??? ??? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ????????? ????????? ????????? ????????? ????????? ?? ?? ?? ?? ?? ??? ??? ??? ??? ??? figure 19. transmit receive timing (short cycle timing) note: 1. external component values are those shown in figure 2. 2. t iming and output amplitudes shown are nominal, and are for the indicated input signal and component values. actual timing and outputs will vary with the application. tai input tlo rlo c t rai input 93 ms 300 ms 200 mvrms, 1.0 khz r x 250 mv tao output rao output 300 ms 200 mvrms, 1.0 khz 200 mv 18 ms 42 ms 430 mvrms 430 mvrms 200 mv idle t x
MC33219A 13 motorola analog ic device data ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?????????? ?????????? ?????????? ?????????? ?????????? ?? ?? ?? ?? ?? ?????????? ?????????? ?????????? ?????????? ?????????? figure 20. transmit receive timing (long cycle timing) note: 1. external component values are those shown in figure 2. 2. t iming and output amplitudes shown are nominal, and are for the indicated input signal and component values. actual timing and outputs will vary with the application. 3. time t 1 depends on the ratio of the onof f amplitude of the signal at t ai. tai input tlo rlo c t rai input 1.0 s 200 mvrms, 1.0 khz tao output rao output 200 mvrms, 1.0 khz 200 mv 430 mvrms 430 mvrms 32 mvrms 250 mv t 1 ?????????? ?????????? ?????????? ?????????? ?????????? 40 ms 72 ms 1.0 s 130 ms 200 mv 225 ms time constant r x idle t x
MC33219A 14 motorola analog ic device data ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?????????? ?????????? ?????????? ?????????? ?????????? ?? ?? ?? ?? ?? ?????????? ?????????? ?????????? ?????????? ?????????? figure 21. transmit receive timing (long cycle timing) note: 1. external component values are those shown in figure 2, except the capacitor at c t is 6.8 m f. 2. t iming and output amplitudes shown are nominal, and are for the indicated input signal and component values. actual timing and outputs will vary with the application. 3. time t 1 depends on the ratio of the onof f amplitude of the signal at t ai. tai input tlo rlo c t rai input 1.0 s 200 mvrms, 1.0 khz tao output rao output 200 mvrms, 1.0 khz 200 mv 430 mvrms 430 mvrms 32 mvrms 250 mv t 1 ?????????? ?????????? ?????????? ?????????? ?????????? 20 ms 32 ms 1.0 s 90 ms 200 mv 100 ms time constant r x idle t x
MC33219A 15 motorola analog ic device data figure 22. chip disable timing note: enable time t 1 depends on the length of t off according to the following chart: cd input (pin 8) t off 5.0 m s ?????????????? ?????????????? ?????????????? ?????????????? ???? ???? ???? ???? ?????????????? ?????????????? ?????????????? ?????????????? ???? ???? ???? ???? figure 23. mute timing output at rao, tao mute input (pin 18) output at mco t 1 1.5 m s 5.0 m s 50 ms 100 ms 500 ms 5.0 s t off 5.0 m s 64 ms 80 ms to 60% 5.0 m s 14 ms 72 ms 100 ms to 100% t 1
MC33219A 16 motorola analog ic device data functional description introduction the fundamental dif ference between the operation of a speakerphone a n d a t elephon e h andse t i s t ha t o f halfduplex versus fullduplex. the handset is full duplex, meaning conversation can occur in both directions (transmit and receive) simultaneously . this is possible due to both the low sound level at the receiver , and the fact that the acoustic coupling from the earpiece to the mouthpiece is almost nonexistent (the receiver is normally held against a person's ear). the loop gain from the receiver to the microphone and through the circuit is well below that needed to sustain oscillations. a speakerphone, on the other hand, has higher gain levels in both the transmit and receive paths, and attempting to converse full duplex results in oscillatory problems due to the loop that exists within the speakerphone circuit. the loop is formed by the hybrid, the acoustic coupling (speaker to microphone), and the transmit and receive paths (between the hybrid and the speaker/microphone). the only practical and economical method used to date is to design the speakerphone to function in a half duplex mode; i.e., only one person speaks at a time, while the other listens. t o achieve this requires a circuit which can detect who is talking (in reality, who is talking louder), switch on the appropriate path (transmit or receive), and switch of f (attenuate) the other path. in this way , the loop gain is maintained less than unity . when the talkers exchange function, the circuit must quickly detect this, and switch the circuit appropriately . by providing speech level detectors, the circuit operates in a ahandsfreeo mode, eliminating the need for a apushtotalko switch. the m c33219 a p rovide s t h e n ecessar y c ircuitr y t o perfor m a v oic e s witched , h al f d uplex , s peakerphone function. the ic includes transmit and receive attenuators, preamplifiers, l eve l d etector s a n d b ackgroun d n oise monitors f o r e ach p ath . a n a ttenuato r c ontro l c ircuit automatically adjusts the gain of the transmit and receive attenuators based on the relative strengths of the voice signals present, the volume control, and the supply voltage (when l ow) . t h e d etectio n s ensitivit y a n d t imin g a re externally controllable. please refer to the block diagram (figure 2) when reading the following sections. transmit and receive attenuators the transmit and receive attenuators are complementary , performing a logantilog function. when one is at maximum gain ( 6.7 db), the other is at maximum attenuation ( 46 db); they are never both fully on or fully of f. both attenuators are controlled by a single output from the attenuator control circuit which ensures the sum of their gains will remain constant at a typical value of 40 db. their p urpos e i s t o p rovid e t h e h alfduple x o peration required in a speakerphone. the attenuators are noninverting, and have a usable bandwidth o f 5 0 k hz . t h e i npu t i mpedanc e o f e ach attenuator (txi and rxi) is nominally 100 k w (see figure 24), and the input signal should be limited to 300 mv rms (850 mv pp) to prevent distortion. that maximum recommended input signal is independent of the volume control setting. both the i npu t a n d o utpu t a r e b iase d a t v b . t h e o utput impedance is <10 w until the output current limit (see specs) is reached. figure 24. attenuator input stage v b tai (rai) v b 90 k 10 k the attenuators are controlled by the single output of the attenuator control circuit, which is measurable at c t (pin 7). when the circuit detects speech signals directing it to the receive mode (by means of the level detectors described below), an internal current source of 90 m a will charge the c t capacitor to a voltage positive with respect to v b (see figure 25). at the maximum volume control setting, this voltage will be approximately 150 mv , and the receive attenuator will have a gain of 6.7 db. when the circuit detects speech signals directing it to the transmit mode, an internal current s ourc e o f 5 0 m a w il l t ak e t h e c apacito r t o approximately 100 mv with respect to v b (the transmit attenuator will have a gain of 6.7 db). when there is no speech present in either path, the current sources are shut off, and the voltage at c t will decay to be equal to v b . this is the idle mode, and the attenuators' gains are nearly halfway between their fully on and fully off positions ( 25 db for the r x attenuator , 16 db for the t x attenuator). monitoring the c t voltage (with respect to v b ) is the most direct method of monitoring the circuit's mode, and its response. the inputs to the attenuator control section are six: the t x r x comparator operated by the level detectors, two background noise monitors, the volume control, the dialtone detector, and the agc circuit. these six functions are described as follows.
MC33219A 17 motorola analog ic device data figure 25. c t attenuator control circuit v b i 1 90 m a to attenuators r t c t t x t x r x comp. vol. control dial tone det. voltage clamps control circuit i 2 50 m a c t MC33219A r x background monitors agc level detectors there are two identical level detectors: one on the receive side and one on the transmit side (refer to figure 26). each level detector is a high gain amplifier with backtoback diodes in the feedback path, resulting in nonlinear gain, which permits operation over a wide dynamic range of speech levels. refer to the graphs of figures 6, 7 and 8 for their dc and ac transfer characteristics. the sensitivity of each level detector is determined by the external resistor and capacitor at their input (tli and rli). the output charges an external capacitor through a diode and limiting resistor , thus providing a dc representation of the input ac signal level. the outputs have a quick rise time (determined by the capacitor and an internal 500 w resistor), and a slow decay time set by an internal current source and the capacitor. the capacitors on the two outputs should have the same value ( 10%) to prevent timing problems. referring to figure 2, the outputs of the two level detectors drive the t x r x comparator . the comparator ' s output state depends on whether the transmit or receive speech signal is stronger, as sensed by the level detectors. the attenuator control circuit uses this signal, along with the background noise monitors, to determine which mode to set. figure 26. level detector tlo (rlo) 1.0 m f 500 w 2.0 m a tli (rli) v b r c signal input external component values are application dependent. background noise monitors the purpose of the background noise monitors is to distinguish s peec h ( whic h c onsists o f b ursts ) f rom background noise (a relatively constant signal). there are two background noise monitors: one for the receive path and one for the transmit path. refering to figure 27, each is operated on by a level detector , which provides a dc voltage representative of the combined speech and noise level. however , the peaks, valleys, and bursts, which are characteristic of speech, will cause the dc voltage (at cp2 or rlo) to increase relatively quickly , causing the output of the next amplifier to also rise quickly . if that increase exceeds the 36 mv of fset, and at a speed faster than the time c onstan t a t c p t ( cpr) , t h e o utpu t o f t h e l ast comparator will change, indicating the presence of speech to the attenuator control circuit. this will keep the circuit in either the transmit or the receive mode, depending on which side has the stronger signals. when a new continuous signal is applied, the time constant at cpt (cpr) determines how long it takes the circuit to decide that the new sound is continuous, and is therefore background noise. the system requires that the average speech signal be stronger than the background noise level (by 6.07.0 db) for proper speech detection. when only background noise is present in both paths, the output of the monitors will indicate the absence of speech, allowing the circuit to go to the idle mode. agc circuit in the receive mode only , the agc circuit decreases the gain of the receive attenuator when the supply voltage at v cc falls below 3.5 v , according to the graph of figure 5. the gain of the transmit path changes in a complementary manner. the purpose of this feature is to reduce the power (and current) used by the speaker when the speakerphone is powered by the phone line, and is connected to a long telephone l ine , w her e t h e a vailable p owe r i s l imited. reducing the speaker power controls the voltage sag at v cc, reduces clipping and distortion at the speaker output, and prevents possible erratic operation.
MC33219A 18 motorola analog ic device data figure 27. background noise monitor 18.6 k 500 w xdi (rli) v b r c signal input 31.7 k v b cp2 (rlo) cpt (cpr) 2.0 m a 36 mv 47 m f 100 k to attenuator control circuit background noise monitor v cc 1.0 m f external component values are application dependent. volume control the volume control input at vlc (pin 19) is sensed as a voltage with respect to v b . the volume control af fects the attenuators in the receive mode only . it has no ef fect in the idle or transmit modes. by varying the voltage at the vlc pin (pin 19), the volume control varies the gain of the attenuators. maximum receive attenuator gain (6.7 db) occurs when vlc = v b . as vlc is reduced below v b , the gain of the receive attenuator is reduced, and the transmit attenuator gain increases in a complementary manner . the usable range of the vlc pin is 1.1 v for v cc 3.5 v , providing a range of 40 db (see figure 4). at v cc < 3.5 v , the range is reduced due to the lower v b voltage, and the agc function. the c onfiguratio n o f t h e e xterna l v olum e c ontrol potentiometer circuit depends on whether the v cc supply voltage is regulated or if it varies, such as in a phone line powered circuit (see figure 28). if the supply voltage is regulated, the circuit on the left can be used. the value of the lower resistor (r 1 ) depends on the value of v cc , so that pin 19 can be varied from v b to 1.1 v below v b . in a phone line powered circuit, the value of v cc , and consequently v b , will vary with line length and with the amount of sound at the speaker . in this case, the circuit on the right side of figure 28 must be used to provide a fixed reference voltage for the potentiometer . with this circuit, the volume setting will not vary when v cc is 3.5 v . as v cc falls below 3.5 v , the zener diode will drop out of regulation, but the agc circuit will ensure that instabilities do not occur. the bias current at vlc flows out of the pin and depends on the voltage at the pin (see figure 16). the capacitor from vlc to v b helps reduce any ef fects of ripple or noise on v b . figure 28. volume control 50 k 50 k r 1 3160 to vlc (pin 19) 0.1 v b volume control to vlc (pin 19) 0.1 volume control v b 6.5 v 6.0 v 5.0 v 4.0 v v cc 86 k 72 k 50 k 25 k r 1 regulated supply unregulated supply lm385-1.2 dial tone detector when the speakerphone is initially taken of fhook, the dial tone signal will switch the circuit to the receive mode. however, since the dial tone is a continuous signal, the MC33219A would consider it as background noise rather than speech, and would therefore switch from receive to idle, causing the dial tone sound level to fade. the dial tone detector prevents the fading by disabling the background noise monitor. the dial tone detector is a comparator with one side connected to the receive attenuator input (rai), and the other input connected to v b with a 20 mv offset (see figure 29). if the circuit is in the receive mode and the incoming signal has peaks greater than 20 mv (14 mv rms), the comparator 's output will change, disabling the receive idle mode. the receive attenuator will then be at a setting determined solely by the volume control. note: the dial tone detector is not a frequency discriminating circuit. figure 29. dial tone detector to attenuator control circuit to r x attenuator v b 20 mv rai microphone amplifier, mute the m icrophon e a mplifier ( pin s 2 0 , 2 1 ) h a s t he noninverting input internally connected to v b , while the inverting input and the output are pinned out. unlike most op amps, the amplifier has an all npn output stage, which maximizes phase margin and gainbandwidth. this feature ensures stability at gains less than unity , as well as with a wide range of reactive loads. the open loop gain is typically 70 db (f < 100 hz), and the gainbandwidth is typically 1.5 mhz. the maximum pp output swing, for 1.0% or less distortion, is shown in figure 14. the output impedance is <10 w until current limiting is reached (typically 2.0 ma peak). the input bias current at mci is typically 30 na out of the pin. the mute function (pin 18), when activated, will reduce the gain of the amplifier by shorting the external feedback resistor (rmf in figure 30). the amplifier is not disabled in this mode; mco remains a low impedance output, and mci remains a virtual ground at v b . the amount of muting (the
MC33219A 19 motorola analog ic device data change in gain) depends on the value of the external feedback resistor , according to the graph of figure 15. muting occurs as the mute input pin is taken from 1.0 v to 1.4 v. the voltage on this pin must be 0.8 v for normal operation, and 2.0 v for muting. see figure 10 for input current requirements. the input must be kept within the range of v cc and gnd. if the input is taken more than 0.4 v above v cc or below gnd excessive currents will flow , and the device' s operation will be distorted. if the mute function is not used, the pin should be grounded. figure 30. microphone amplifier and mute v cc v b r mi from microphone 50 k 50 k mute r mf mco mci receive amplifier the receive amplifier (pins 16, 17) has the noninverting input internally connected to v b , while the inverting input and the output are pinned out. unlike most op amps, the amplifier has an all npn output stage, which maximizes phase margin and gainbandwidth. this feature ensures stability at gains less than unity , as well as with a wide range of reactive loads. the open loop gain is typically 70 db (f < 100 hz), and the gainbandwidth is typically 1.5 mhz. the maximum pp output swing for 1.0% or less distortion is shown in figure 14. the output impedance is <10 w until current limiting is reached (typically 2.0 ma peak). the input bias current at rxi is typically 30 na out of the pin. power supply, v b and chip disable the power supply voltage at pin 24 is to be between 3.5 and 6.5 v for normal operation, and down to 2.7 v with the agc in ef fect (see agc section). the supply current required is typically 3.2 ma in the idle mode, and 4.0 ma in the transmit and receive modes. figure 1 1 shows the supply current for both the normal and disabled modes. the output voltage at v b (pin 6) is approximately equal to (v cc 0.7)/2, and provides an ac ground for the internal amplifiers and the system. the output impedance at v b is approximately 600 w , and in conjunction with the external capacitor at v b forms a low pass filter for power supply noise rejection. the choice of the v b capacitor size is application dependent based on whether the circuit is powered by the telephone line or a regulated supply . see figure 13 for psrr information. since v b biases the microphone and receive amplifiers, the amount of supply rejection at their outputs is a function of the rejection at v b , as well as the gains of the amplifiers. the amount of current which can be sourced out of the v b pin depends on the v cc voltage (see figure 12). drawing current in excess of that shown in figure 12 will cause v b to drop low enough to disrupt the circuit' s operation. this pin can sink 100 m a when enabled, and 0 m a when disabled. the chip disable (pin 8) permits powering down the ic for power conservation. with cd between 0 and 0.8 v , normal operation is in ef fect. with cd between 2.0 v and v cc , the ic is powered down, and the supply current drops to about 1 10 m a (at v cc = 5.0 v , see figure 1 1). when cd is high, the microphone and receive amplifiers, the level detectors, a n d t h e t w o a ttenuator s a r e d isable d ( their outputs go to a high impedance). the background noise monitors are disabled, and pins 3 and 10 will go to v cc . the v b output, however , remains active, except that it cannot sink any current. the cd input must be kept within the range of v cc and gnd. see figure 9 for input current requirements. if the input is taken more than 0.4 v above v cc or below gnd excessive currents will flow , and the device' s operation will be distorted. if the disable function is not used, the pin should be connected to ground.
MC33219A 20 motorola analog ic device data applications information switching and response time theory the switching time of the MC33219A circuit is dominated first by the components at c t (pin 7, see figure 2), and second by the capacitors at the level detector outputs (rlo, tlo). the transition time to receive o r t o transmit mode from either idle or the other mode is determined by the capacitor at c t , a lon g w it h t h e i nterna l c urren t s ource s ( refe r t o figure 25). the switching time is: t v c t i when switching from idle to receive, d v = 150 mv , i = 90 m a, the c t capacitor is 15 m f , and d t calculates to 25 ms. when switching from idle to transmit, d v = 100 mv, i = 50 m a, the c t capacitor is 15 m f , and d t calculates to 30 ms. when the circuit switches to idle, the internal current sources are shut off, and the time constant is determined by the c t c apacito r a n d r t , t h e e xterna l r esistor ( see figure 25). with c t = 15 m f , and r t = 15 k w , the time constant is 225 ms, giving a total switching time of 0.68 s (for 95% change). the switching period to idle begins when both speakers have stopped talking. the switching time back to the original mode will depend on how soon that speaker begins speaking again. the sooner the speaking starts during the adecay to idleo period, the quicker the switching time, since a smaller voltage excursion is required. that switching time is determined by the internal current sources as described above. when t h e c ircui t s witche s d irectl y f ro m r eceiv e t o transmit (or vice versa), the total switching time depends not only on the components and currents at the c t pin, but also on the response of the level detectors, the relative amplitude of the two speech signals, and the mode of the circuit, s inc e t h e t w o l eve l d etector s a r e c onnected differently to the two attenuators. the rise time of the level detector ' s outputs (rlo, tlo) is not significant since it is so short. the decay time, however , provides a significant part of the ahold timeo necessary to hold the circuit (in transmit or receive) during the normal pauses in speech. the capacitors at the two outputs must be equal value ( 10%) to prevent problems in timing and level response. the components at the inputs of the level detectors (rli, tli) do not af fect the switching time, but rather af fect the relative signal levels required to switch the circuit, as well as the frequency response of the detectors. they must be adjusted for proper switching response as described later in this section. switching and response time measurements using burst of 1.0 khz sine waves to force the circuit to switch among its modes, the timing results were measured and are indicated in figures 1721. a) in figure 17, when a signal is applied to the transmit attenuator o nl y ( normall y v i a t h e m icrophon e a n d t he microphone a mplifier) , t h e t ransmi t b ackgroun d n oise monitor immediately indicates the apresence of speecho as evidenced by the fact that cpt begins rising. the slope of the rising cpt signal is determined by the external resistor and c apacito r o n t hat p in . e ve n t houg h t h e t ransmit attenuator is initially in the idle mode (16 db), there is sufficient signal at its output to cause tlo to increase. the attenuator control circuit then forces the circuit to the transmit mode, evidenced by the change at the c t pin. the attenuator output signal is then 6.7 db above the input. with the steady sine wave applied to the transmit input, the circuit will stay in the transmit mode until the cpt pin gets to within 36 mv of its final value. at that point, the internal comparator (see figure 27) switches, indicating to the attenuator control circuit that the signal is not speech, but rather it is a steady background noise. the circuit now begins to decay to idle, as evidenced by the change at c t and tlo, and the change in amplitude at tao. when the input signal at tai is removed (or reduced), the cpt pin drops quickly , allowing the circuit to quickly respond to any new speech which may appear afterwards. the voltage at c t decays according to the time constant of its external components, if not already at idle. the voltage change at cp2, cpt , and t ao depends on the input signal' s amplitude and the components at xdi and tli. the change at c t is internally fixed at the level shown. the timing numbers shown depend both on the signal amplitudes and the components at the c t and cpt pins. b) figure 18 indicates what happens when the same signal is applied to the receive side only . rlo and cpr react similarly to tlo and cpt . however , the circuit does not switch to idle when cpr finishes transitioning since the dial tone detector disables the background noise monitor , allowing the circuit to stay in the receive mode as long as there is a signal present. if the input signal amplitude had been less than the dial tone detector ' s threshold, the circuit response would have been similar to that shown in figure 17. the voltage change at c t depends on the setting of the volume control (pin 19). the 150 mv represent maximum volume setting. c) f igur e 1 9 i ndicate s t h e c ircuit r espons e w he n t ransmit and r eceiv e s ignal s a r e a lternatel y a pplied , w it h r elativel y s hort cycle times (300 ms each) so that neither attenuator will begin to go to idle during its aono time. figure 20 indicates the circuit response w it h l onge r c ycl e t ime s ( 1. 0 s e ach) , w her e t he transmit side is allowed to go to idle. figure 21 is the same as figure 20, except the capacitor at c t has been reduced from 15 m f t o 6 .8 m f , p rovidin g a q uicke r s witchin g t ime . t he reactions a t t h e v ariou s p in s a r e s hown . t h e r espons e t ime s a t tao an d r a o a re different, and typicall y s lightl y l onger than what is shown in figures 17 and 18 due to: the larger transition required at the c t pin, the greater difference in the levels at rlo and tlo due to t h e p osition s o f t h e a ttenuator s a s w el l a s t hei r d ecay time, and response time of the background noise monitors. the timing responses shown in these three figures are representative for those input signal amplitudes and burst durations. actual response time will vary for dif ferent signal conditions. note: while it may seem desirable to decrease the switching time between modes by reducing the capacitor at c t , this should be done with caution for two reasons: 1) if th e s witching time i s t o o s hort, th e c ircui t r esponse may appear to be atoo quicko to the user, who may consider its operation erratic. the recommended values in this data sheet, a lon g w it h t h e a ccompanyin g t imings , p rovid e w hat
MC33219A 21 motorola analog ic device data experience h a s s how n t o b e a a comfortabl e r esponse o b y the circuit. 2) the distortion in the receive attenuator will increase as the c t capacitor value is decreased. the extra thd will be most noticeable at the lower frequencies and at the lower ampitudes. table 1 provides a guideline for this issue. table 1. thd versus c t capacitor c t capacitor idle r x transition input @ rai freq. thd @ rao 15 m f 25 ms 20 mvrms 300 hz 1.2% 1.0 khz 0.25% 100 mvrms 300 hz 0.5% 1.0 khz 0.2% 6.8 m f 12 ms 20 mvrms 300 hz 5.0% 1.0 khz 0.7% 100 mvrms 300 hz 1.3% 1.0 khz 0.35% 3.0 m f 5.0 ms 20 mvrms 300 hz 11% 1.0 khz 1.8% 100 mvrms 300 hz 2.6% 1.0 khz 0.7 % considerations in the design of a speakerphone the design and adjustment of a speakerphone involves human interface issues as well as proper signal levels. because of this fact, it is not practical to do all of the design mathematically. certain parts of the design must be done by trial and error , most notably the switching response and the ahow does it sound?o part of the testing. among the recommendations for a successful design are: 1) d esig n t h e e nclosure concurrently with t he electronics. do not leave the case design to the end as its properties are just as important (just as equally important) as the electronics. one of the major issues involved in a speakerphone design is the acoustic coupling of the speaker to t h e m icrophone , w hic h m ust b e m inimized . t his parameter is dependent entirely on the design of the enclosure, the mounting of the speaker and the microphone, and their characteristics. 2) ensure the speaker is optimally mounted. this fact alone can make a difference of several db in the sound level from the speaker , as well as the sound quality . the speaker manufacturer should be consulted for this information. 3) do not breadboard the circuit with the microphone and speaker hanging out in midair . it will not work. the speaker and microphone must be in a suitable enclosure, preferably one resembling the end product. if this is not feasible, temporarily use some other properly designed enclosure, such as one of the many speakerphones on the market. 4) do not breadboard the circuit on a wirewrapped board or a plugin prototyping board. use a pc board, preferably with a ground plane. proper filtering of the supply voltage at the v cc pin is essential. 5) the speakerphone must be tested with the intended hybrid and connected to a phone line or phone line simulator . the performance of the hybrid is just as important as the enclosure and the speakerphone ic. 6) when testing the speakerphone, be conscious of the environment. if the speakerphone is in a room with large windows and tile floors, it will sound dif ferent than if it is in a carpeted room with drapes. additionally, be conscious of the background noise in a room. 7) when testing the speakerphone on a phone line, make sure the person at the other end of the phone line is not in the same room as the speakerphone. design procedure a r ecommende d s equenc e f ollow s i n f igur e 31, assuming the end product enclosure is available, with the intended production microphone and speaker installed, and the pc boards or temporary substitutes installed. figure 31. basic block diagram for design purposes acoustic coupling control hybrid g st (g ac ) v 1 tip ring r 1 v 2 r 2 r x attenuator v m mci mike amp speaker amp rao mco rai tao tai i 1 i 2 rxo rxi tli rli t x attenuator speaker microphone
MC33219A 22 motorola analog ic device data 1) design the hybrid, ensuring proper interface with the phone line for both dc and ac characteristics. the return loss must be adjusted to comply with the appropriate regulatory agency . the sidetone should then be adjusted according to the intent of the product. if the product is a speakerphone only (without a handset), the sidetone gain (gst) should be adjusted for maximum loss. if a handset is part of the end product, the sidetone must be adjusted for the minimum a cceptabl e s ideton e l evels i n t h e h andset. generally, f o r t h e s peakerphon e i nterface , 1 02 0 d b sidetone loss is preferred for gst. 2) check the acoustic coupling of the enclosure (gac in figure 31). with a steady sound coming out of the speaker , measure the rms voltage on the speaker terminals and the rms voltage out of the microphone. experience has shown that the loss should be at least 40 db, preferably 50 db. this should be checked over the frequency range of 20 hz to 10 khz. 3) adjust the transmit path for proper signal levels, based on the lowest speech levels as well as the loudest. based on the typical levels from commonly available microphones, a gain of about 3545 db is required from the microphone terminals to t ip and ring. most of that gain should be in the microphone amplifier to make best use of the transmit attenuator, but the maximum input level at t ai must not be exceeded. i f a s igna l g enerato r i s u sed i nstea d o f a microphone for testing, the circuit can be locked into the transmit m od e b y g roundin g c p t ( pi n 3 ) . f requency response can generally be tailored with capacitors at the microphone amplifier. 4) adjust the receive path for proper signal levels based on the lowest speech levels as well as the loudest. a gain of about 30 db is required from t ip and ring to the speaker terminals for most applications (at maximum volume). most of that gain should be in the receive amplifier (at rxi, rxo) to make best use of the receive attenuator , but the maximum input level at rai must not be exceeded. if a signal generator is used for signal injection during testing, the circuit can be locked into the receive mode by grounding cpr (pin 10), although this is usually not necessary since the dial tone detector will keep the circuit in the receive mode. frequency response can generally be tailored with capacitors at the receive amplifier. 5) check that the loop gain (i.e., the receive path gain + acoustic coupling gain + transmit path gain + sidetone gain) is less than 0 db over all frequencies. if not, asingingo will occur: a steady oscillation at some audible frequency. 6) a) the final step is to adjust the resistors at the level detector inputs (rli and tli) for proper switching response (the switchpoint occurs when i 1 = i 2 ). this has to be the last step, as the resistor values depend on all of the above adjustments, which are based on the mechanical, as well as the electrical, characteristics of the system. note: an extreme case of level detector misadjustment can result in amotorboatingo. in this condition, with a receive signal applied, sound from the speaker enters the microphone, and causes the circuit to switch to the transmit mode. this causes the speaker sound to stop (as well as the sound into the microphone), allowing the circuit to switch back to the receive mode. this sequence is then repeated, usually , at a rate of a few hz. the first thing to check is the acoustic coupling, and then the level detectors. b) starting with the recommended values for r 1 and r 2 (in figure 2), hold a normal conversation with someone on another phone. if the resistor values are not optimum, one of the talkers will dominate, and the other will have dif ficulty getting t hrough . i f , f or e xample , t h e p erso n a t t he speakerphone is dominant, the transmit path is overly sensitive, and the receive path is not sensitive enough. in this case, r 1 (at tli) should be increased, or r 2 (at rli) decreased, or both. their exact value is not critical at this point, only their relative value. keeping r 1 and r 2 in the range of 2.020 k, adjust them until a suitable switching response is found. c) then have the person at the other end of the phone line speak loud continuously , or connect to a recording which is somewhat s trong . m onito r t h e s tat e o f t h e c ircui t ( by measuring the c t versus v b pins, and by listening carefully to the speaker) to check that the sound out of the speaker is not attempting to switch the circuit to the transmit side (through acoustic coupling). if it is, increase r 1 (at tli) in small steps just enough to stop the switching (this desensitizes the transmit side). if r 1 has been changed a large amount, it may be necessary to readjust r 2 for switching response. if this cannot be achieved in a reasonable manner , the acoustic coupling is too strong. d) next, have the person at the speakerphone speak somewhat loudly , and again monitor the state of the circuit, primarily by having the person at the other end listen carefully for fading. if there is obvious fading of the sound, increase r 2 so as to desensitize the receive side. increase r 2 just enough to stop the fading. if this cannot be achieved in a reasonable manner, the sidetone coupling is too strong. e) if necessary , readjust r 1 and r 2 a small amount relative to each other , to further optimize the switching response. transmit/receive detection priority although the MC33219A was designed to have an idle mode such that the transmit side has a small priority (the idle mode position is closer to the full transmit side), the idle mode position can be moved with respect to the transmit or the receive side. with this done, the ability to gain control of the circuit by each talker will be changed. by connecting a resistor from c t (pin 7) to ground, the circuit will be biased more towards the transmit side. the resistor value is calculated from: r r t v b v 1 where r is the added resistor , r t is the resistor normally between pins 6 and 7 (typically 15 k w ), and d v is the desired change in the c t voltage at idle. by connecting a resistor from c t (pin 7) to v cc , the circuit will be biased towards the receive side. the resistor value is calculated from: r r t v cc v b v 1 r, r t , and d v are the same as above. switching response and the switching time will be somewhat af fected in each case due to the dif ferent voltage excursions required to get to transmit and receive from idle. for practical considerations, the d v shift should not exceed 50 mv. disabling the idle mode for testing or circuit analysis purposes, the transmit or receive attenuators can be set to the on position, even with steady signals applied, by disabling the background noise monitors. grounding the cpr pin will disable the receive background noise monitor , thereby indicating the apresence
MC33219A 23 motorola analog ic device data of speecho to the attenuator control block. grounding cpt does the same for the transmit path. additionally, the receive background noise monitor is automatically disabled by the dial tone detector whenever the receive signal exceeds the detector's threshold. dial tone detector threshold the threshold for the dial tone detector is internally set at 20 mv (14 mv rms) below v b (see figure 29). that threshold can be adjusted if desired by changing the bias at rai. the method used depends on how the input of the receive attenuator is connected to other circuitry. a) if the attenuator input (rai) is dc coupled to the receive amplifier (pins 15 to 16 as in figure 2), or to some other amplifier in the system, then the threshold is changed by forcing a small of fset on that amplifier . as shown in figure 32, connect a resistor (r t o) from the summing node to either ground or v cc , depending on whether the dial tone detector threshold is to be increased or decreased. rf and ri are the resistors normally used to set the gain of that amplifier. figure 32. adjusting dial tone detector threshold (dc coupled) ri audio signal input 100 k rxo rto v cc or gnd v b v b rxi rf rai 20 mv v b attenuator to attentuator control circuit adding rt o and connecting it to ground will shift rxo and rai upward, thereby increasing the dial tone detector threshold. in this case, rto is calculated from: rto v b rf v v b is the voltage at pin 6, and d v is the amount that the detector's threshold is increased. for example, if v b = 2.2 v, and rf = 10 k, and the threshold is to be increased by 20 mv , rto calculates to 1.1 m w . connecting rt o to v cc will shift rxo downward, thereby decreasing the dial tone detector threshold. in this case, r to is calculated from: rto ( v cc v b ) rf v for example, if v cc = 5.0 v, v b = 2.2 v, and rf = 10 k and the threshold is to be decreased by 10 mv , rt o calculates to 2.8 m w. b) if the receive attenuator input is ac coupled to the receive amplifier or to other circuitry, then the of fset is set at rai. the circuits in figure 33 are suggested for changing the threshold. figure 33. adjusting dial tone detector threshold (ac coupled) audio signal input v cc 3.0 k 56 k rto rai v b to increase the threshold to decrease the threshold 100 k v b 20 mv v b attenuator to control circuit dtd audio signal input rto rai 100 k v b 20 mv v b attenuator to control circuit dtd 56 k 3.0 k v b to increase the threshold, use the first circuit in figure 33. the voltage at the top of the 3.0 k resistor is between 90 and 180 mv above v b (depending on v cc ). rto and the 100 k input impedance form a voltage divider to create the desired offset at rai. rto is calculated from: rto (( v cc v b ) 0.05 ) v 1 ( 100 k ) for example, if v cc = 5.0 v , and the threshold is to be increased by 20 mv ( d v), rto calculates to 600 k w . if the threshold is to be decreased, use the second circuit in figure 33. rto is calculated from: rto ( v b 0.05 ) v 1 ( 100 k ) rfi interference potential radio frequency interference (rfi) problems should be addressed early in the electrical and mechanical design of the speakerphone. rfi may enter the circuit through t ip and ring, through the microphone wiring to the microphone amplifier (which should be short), or through any of the pc board traces. the most sensitive pins on the MC33219A are the inputs to the level detectors (rli, tli, xdi) since, when there is no speech present, the inputs are high impedance and these op amps are in a near openloop condition. the board traces to these pins should be kept
MC33219A 24 motorola analog ic device data short, and the resistor and capacitor for each of these pins should be physically close to the pins. all other input pins should also be considered sensitive to rfi signals. in the final analysis ... proper operation of a speakerphone is a combination of proper mechanical (acoustic) design in addition to proper electronic design.the acoustics of the enclosure must be considered early in the design of a speakerphone. in general, electronics cannot compensate for poor acoustics, low s peake r q uality , l o w m icrophon e q uality , o r a ny combination of these items. proper acoustic separation of the speaker and microphone is essential. the physical location of the microphone, along with the characteristics of the selected microphone, will play a large role in the quality of the transmitted sound. the microphone and speaker vendors can usually provide additional information on the use of their products. in the final analysis, the circuit will have to be finetuned to match the acoustics of the enclosure, the specific hybrid, and the s pecifi c s peake r a n d m icrophon e s elected. t he components shown in this data sheet should be considered as starting points only. the gains of the transmit and receive paths are easily adjusted at the microphone and receive amplifiers, respectively. the switching response can then be fine tuned by varying (in small steps) the components at the level detector inputs (tli, rli) until satisfactory operation is obtained for both long and short lines. for additional information on speakerphone design please refer to the bell system t echnical journal, v olume xxxix (march 1960, no. 2).
MC33219A 25 motorola analog ic device data glossary a t t en u at i o n a d ec r eas e i n m agnit ud e o f a communication signal, usually expressed in db. bandwidth t h e r ang e o f i nformation c arrying frequencies of a communication system. battery the voltage which provides the loop current to the telephone from the co. the name is derived from the fact that cos have always used batteries, in conjunction with ac power, to provide this voltage. cmessage f ilter a f requenc y w eighting w hich evaluates the ef fects of noise on a typical subscriber 's system. central office abbreviated co, it is a main telephone office, usually within of a few miles of its subscribers, that houses s witchin g g ea r f o r i nterconnectio n w ithi n i ts exchange area, and to the rest of the telephone system. a co can handle up to 10,000 subscriber numbers. co see central office. codec coder/decoder in the central of fice, it converts the transmit signal to digital, and converts the digital receive signal to analog. db a power or voltage measurement unit, referred to another power or voltage. it is generally computed as: 10 x log (p 1 /p 2 ) for power measurements, and 20 x log(v 1 /v 2 ) for voltage measurements. dbm an indication of signal power . 1.0 mw across 600 w , or 0.775 v rms, is defined as 0 dbm. any other voltage level is converted to dbm by: dbm = 20 x log (vrms/0.775), or dbm = [20 x log (vrms)] + 2.22. d b m p i ndic at e s d b m m eas ur emen t u s in g a psophometric weighting filter. dbrn indicates a dbm measurement relative to 1.0 pw power l eve l i nt o 6 00 w . g enerall y u se d f o r n oise measurements, 0 dbrn = 90 dbm. dbrnc i ndicate s a d br n m easuremen t u sin g a cmessage weighting filter. dtmf dual tone multifrequency. it is the atone dialingo system based on outputting two nonharmonic related frequencies simultaneously to identify the number dialed. eight frequencies have been assigned to the four rows and four columns of a keypad. four wire circuit the portion of a telephone, or central office, which operates on two pairs of wires. one pair is for the transmit path, and one pair is for the receive path. full duplex a transmission system which permits communication i n b ot h d irection s s imultaneously . t he standard handset telephone system is full duplex. gain the change in signal amplitude (increase or decrease) after passing through an amplifier or other circuit stage. usually expressed in db, an increase is a positive number and a decrease is a negative number. half duplex a transmission system which permits communication in one direction at a time. cb radios, with apushtotalko switches, and voice activated speakerphones are half duplex. hookswitch a switch within the telephone which connects the telephone circuit to the subscriber loop. the name is derived from old telephones where the switch was activated by lifting the receiver of f and onto a hook on the side of the phone. hybrid a twotofour wire converter. idle channel noise residual background noise when transmit and receive signals are absent. line card the printed circuit board and circuitry in the co or pbx which connects to the subscriber's phone line. a line card may hold circuitry for one subscriber or a number of subscribers. longitudinal balance the ability of the telephone circuit to reject longitudinal signals on tip and ring. longitudinal signals common mode signals. loop the loop formed by the two subscriber wires (t ip and ring) connected to the telephone at one end, and the central of fice (or pbx) at the other end. generally it is a floating system, not referred to ground, or ac power. loop current the dc current which flows through the subscriber loop. it is typically provided by the central of fice or pbx, and ranges from 20120 ma. mute reducing the level of an audio signal, generally so that i t i s i naudible . p artia l m utin g i s u se d i n s ome applications. of f h ook t h e c onditio n w he n t h e t elephon e i s connected to the phone system, permitting the loop current to flow. the central of fice detects the dc current as an indication that the phone is busy. on h ook t h e c onditio n w he n t h e t elephon e i s disconnected from the phone system, and no dc loop current flows. the central of fice regards an on hook phone as available for ringing. pabx private automatic branch exchange. in ef fect, a miniature central of fice; it is a customer owned switching system servicing the phones within a facility , such as an office building. a portion of the p abx connects to the bell (or other local) telephone system. power supply rejection ratio the ability of a circuit to reject outputting noise or ripple, which is present on the power supply lines. psrr is usually expressed in db. protection, primary usually consisting of carbon blocks or gas discharge tubes, it absorbs the bulk of a lightning induced transient on the phone line by clamping the voltages to less than 1500 v. protection, secondary usually located within the telephone, it protects the phone circuit from transient surges. typically, it must be capable of clamping a 1.5 kv surge of 1.0 ms duration. pulse dialing a dialing system whereby the loop current is interrupted a number of times in quick succession. the number of interruptions corresponds to the number dialed, and the interruption rate is typically 10 per second. the old rotary phones and many new pushbutton phones use pulse dialing. receive path within the telephone, it is the speech path from the phone line (t ip and ring) towards the receiver or speaker. ren ringer equivalence number . an indication of the impedance (or loading factor) of a telephone bell or ringer circuit. an ren of 1.0 equals 8.0 k w . the bell system typically permits a maximum of 5.0 ren (1.6 k w ) on an individual subscriber line. a minimum ren of 0.2 (40 k w ) is required by the bell system.
MC33219A 26 motorola analog ic device data return loss expressed in db, it is a measure of how well the telephone' s ac impedance matches the line' s ac characteristic impedance. with a perfect match, there is no reflected signal, and therefore infinite return loss. it is calculated from: rl 20 log ( z line z ckt ) ( z line z ckt ) ring one of the two wires connecting the central office to a telephone. the name is derived from the ring portion of the plugs used by operators (in older equipment) to make the connection. ring is traditionally negative with respect to tip. sidetone rejection the rejection (in db) of the reflected signal in the receive path resulting from a transmit signal applied to the phone and phone line. slic subscriber line interface circuit. it is the circuitry within the co or pbx which connects to the user ' s phone line. subscriber the customer at the telephone end of the line. subscriber line the system consisting of the user 's telephone, the interconnecting wires, and the central of fice equipment dedicated to that subscriber (also referred to as a loop). tip one of the two wires connecting the central of fice to a telephone. the name is derived from the tip of the plugs used b y o perator s ( i n o lde r e quipment ) t o m ak e t he connection. tip is traditionally positive with respect to ring. transmit path within the telephone it is the speech path from the microphone towards the phone line (t ip and ring). two wire circuit refers to the two wires connecting the central of fice to the subscriber ' s telephone. commonly referred to as t ip and ring, the two wires carry both transmit and receive signals in a differential manner. twotofour wire converter a circuit which has four wires (on one side): two (signal and ground) for the outgoing signal and two for the incoming signal. the outgoing signal is sent out dif ferentially on the two wire side, and incoming differential signals received on the two wire side are directed to the receive path of the four wire side. additional circuit within cancels the reflected outgoing signal to keep it separate from the incoming signal. voiceband that portion of the audio frequency range used for transmission across the telephone system. t ypically it is 3003400 hz. suggested vendors microphones primo microphones inc. bensenville, il 60106 180076primo telecom transformers microtran co., inc. stancor products valley stream, ny 11528 logansport, in 46947 5165616050 2197222244 various models ask for catalog various models ask for catalog and application bulletin f232 prem magnetics, inc. mchenry, il 60050 8153852700 various models ask for catalog motorola does not endorse or warrant the suppliers referenced.
MC33219A 27 motorola analog ic device data min max millimeters 1.27 bsc 2.54 bsc 7.62 bsc 31.25 6.35 3.69 0.38 1.02 0.18 2.80 0 0.51 32.13 6.85 4.44 0.51 1.52 0.30 3.55 15 1.01 min max inches 1.265 0.270 0.175 0.020 0.060 0.012 0.140 15 0.040 0.050 bsc 0.100 bsc 0.300 bsc 1.230 0.250 0.145 0.015 0.040 0.007 0.110 0 0.020 dw suffix plastic package case 751e04 outline dimensions p suffix plastic package case 72403 t 0.010 (0.25) a b m s s min min max max millimeters inches dim a b c d f g j k m p r 15.25 7.40 2.35 0.35 0.41 0.23 0.13 0 10.05 0.25 15.54 7.60 2.65 0.49 0.90 0.32 0.29 8 10.55 0.75 0.601 0.292 0.093 0.014 0.016 0.009 0.005 0 0.395 0.010 0.612 0.299 0.104 0.019 0.035 0.013 0.011 8 0.415 0.029 1.27 bsc 0.050 bsc notes: 1. dimensioning and tolerancing per ansi y14.5m, 1982. 2. controlling dimension: millimeter. 3. dimensions a and b do not include mold protrusion. 4. maximum mold protrusion 0.15 (0.006) per side. 5. dimension d does not include dambar protrusion. allowable dambar protrusion shall be 0.13 (0.005) total in excess of d dimension at maximum material condition. a b 1 12 24 13 t c k seating plane r x 45 g 22 pl p 12 pl 0.010 (0.25) b m m f j m d 24 pl dim a b c d e f g j k l m n notes: 1. chamfered contour optional. 2. dimension l to center of leads when formed parallel. 3. dimensioning and tolerancing per ansi y14.5m, 1982. 4. controlling dimension: inch. 1 12 13 24 a b c k n t seating plane g e f d 24 pl j 24 pl m note 1 l 0.25 (0.010) t a m m 0.25 (0.010) t b m m
MC33219A 28 motorola analog ic device data motorola reserves the right to make changes without further notice to any products herein. motorola makes no warranty , representation or guarantee regarding the suitability of its products for any particular purpose, nor does motorola assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability , including without limitation consequential or incidental damages. at ypicalo parameters can and do vary in dif ferent applications. all operating parameters, including at ypicalso must be validated for each customer application by customer ' s technical experts. motorola does not convey any license under its patent rights nor the rights of others. motorola products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body , or other applications intended to support or sustain life, or for any other application in which the failure of the motorola product could create a situation where personal injury or death may occur . should buyer purchase or use motorola products for any such unintended or unauthorized application, buyer shall indemnify and hold motorola and its of ficers, employees, subsidiaries, af filiates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly , any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that motorola was negligent regarding the design or manufacture of the part. motorola and are registered trademarks of motorola, inc. motorola, inc. is an equal opportunity/af firmative action employer . literature distribution centers: usa/europe: motorola literature distribution; p .o. box 20912; phoenix, arizona 85036. jap an: nippon motorola ltd.; 4321, nishigotanda, shinagawaku, t okyo 141, japan. asia p acific: motorola semiconductors h.k. ltd.; silicon harbour center , no. 2 dai king street, t ai po industrial estate, t ai po, n.t., hong kong. MC33219A/d
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