1 multimedia ics analog compander for karaoke echo systems ba7725s / ba7725fs the ba7725s and ba7725fs are analog companders designed for karaoke echo systems, and logarithmically compress the signal level by 1 / 2 and then logarithmically expand it by a factor of 2. these ics can be used in com- bination with the bu9252s or bu9252f to create a digital echo system. these ics have an internal line mixer ampli- fier for mixing line input and echo signals. the internal electronic volume control makes it possible to adjust the mixer level and loop level mixer with an external dc voltage. applications circuits that require analog signal compression and expansion features 1) internal logarithmic 1 / 2 compression circuit and 2 expansion circuit 2) internal 2-channel buffer amplifier used as a tertiary low pass filter 3) internal mixer amplifier that mixes line input and microphone input 4) internal electronic volume control allows for adjust- ment of the echo mixer level and loop mixer level using an external dc voltage. 5) internal microphone amplifier and microphone input on / off switch absolute maximum ratings (ta = 25?) parameter symbol limits unit power supply voltage v cc 13 v power dissipation ba7725s 1000 * 1 mw 600 * 2 ba7725fs storage temperature c operating temperature c ?55 ~ + 125 ?10 ~ + 70 pd tstg topr * 1 reduced by 10mw for each increase in ta of 1 c over 25 c. * 2 reduced by 6.0mw for each increase in ta of 1 c over 25 c. recommended operating conditions parameter symbol limits unit power supply voltage v v cc 6.5 ~ 12.0
2 multimedia ics ba7725s / ba7725fs block diagram ba7725s ba7725fs 22 21 20 19 18 17 16 15 14 13 12 10 9 8 7 6 5 4 3 2 1 20 19 18 17 16 15 14 13 12 11 11 1 2 3 4 5 6 7 8 9 10 sw vr vr bf expand bf bf bf bf expand vr vr sw mic amp in mic amp out n.c. n.c. gnd gnd dly bf out exp bf in exp bf out exp det ct exp det loop gain ctrl echo lev ctrl line in line out compress compress ripple filter cmp det cmp det ct cmp out cmp bf in cmp bf out dly bf in line out line in echo lev ctrl loop gain ctrl exp det exp det ct exp bf out exp bf in dly bf out mic amp in mic amp out ripple filter cmp det cmp det ct cmp out cmp bf in cmp bf out dly bf in v cc + + + + + + v cc bf
3 multimedia ics ba7725s / ba7725fs pin descriptions pin name function ba7725s ba7725fs 1 1 line out line output 2 2 line in line input 3 n.c. 4 3 echo lev ctrl microphone turns off when voltage drops below 1v. set echo signal damping ratio between 2-9v (vcc = 9.0v). 5 4 gnd ground 6 5 loop gain ctrl setting the loop damping ratio. set between 2-9v (vcc = 9.0v). 7 6 exp det expand detection 8 7 exp det ct 9 8 exp bf out lpf bf output (expansion) 10 9 exp bf in lpf bf input (expansion) 11 10 dly bf out echo signal input bf output 12 11 dly bf in echo signal input bf input 13 12 cmp bf out lpf bf output (compression) 14 13 cmp bf in lpf bf input (compression) 15 14 cmp out compression output 16 15 cmp det ct 17 16 cmp det compression detection 18 17 ripple fiter attached ripple rejection capacitor 19 18 20 n.c. 21 19 mic amp out microphone amplifier output 22 20 mic amp in microphone amplifier input setting expand attack / recovery time attack (r) = 5.6k w , recovery (r) = 85.6k w setting the compression attack / recovery time attack (r) = 5.6k w , recovery (r) = 85.6k w v cc v cc pin no.
4 multimedia ics ba7725s / ba7725fs input / output circuits pin name pin no. equivalent circuit echo level ctrl 4 loop gain ctrl 6 note: the ba7725fs is mounted on a 20-pin ssop-a package with a different pin number than the ba7725s. on the ba7725fs, the echo level ctrl pin is pin 3, and the loop gain ctrl pin is pin 5. 4 6
5 multimedia ics ba7725s / ba7725fs electrical characteristics (unless otherwise noted, ta = 25?, vcc = 9v) parameter symbol min. typ. max. unit conditions supply current i cc 4.3 5.7 7.6 ma no input line through output level v oll ?9.0 ?8.0 7.0 dbv v in = ?26.0dbv line through output distortion thd ll 0.15 0.5 % line through maximum output level v oml + 5.0 + 7.2 dbv line through noise level v onl 92 77 dbv microphone through output level v oml ?10.5 8.5 ?6.5 dbv v in = ?52dbv microphone through output distortion thd ml 0.2 0.5 % microphone through input conversion noise v onm 114 104 dbv input shorted microphone through crosstalk ct ml 91 75 dbv compress output level v omc 6.5 4.5 2.5 dbv v in = ?52dbv compress output distortion thd mc 0.5 2.0 % compress noise level v onc 55 45 dbv compress characteristics cmp 11.0 db v odl1 ?11.7 9.7 dbv v in = ?5.0dbv, v 4 = 9.0v expand output distortion thd dl 0.25 2.0 % expand characteristic exp 19.5 db v odl2 54 44 db v odc1 ?7.5 5.5 dbv v in = ?5.0dbv, v 6 = 9.0v v odc2 42 ?32 dbv mic off holding voltage v 4off 0.0 1.0 v mic on holding voltage v 4on 2.0 9.0 v v in = 42dbv ? 62dbv output level differential expand output level 1 expand output level 2 v in = 0dbv ? 10.0dbv output level differential v in = 5.0dbv, output level differential relative to vo dl1 v in = ?5.0dbv, output level differential relative to vo dc1 loop output level 1 loop output level 2 line through ? input : line in, output : line out mic through ? input : mic amp in, output : line out compress ? input : mic amp in, output : cmp bf out expand ? input : dly bf in, output : line out loop ? input : dly bf in, output : cmp bf out mode holding voltage ? unless otherwise noted, v4 = 9.0v (mic on), v6 = 9.0v (max. loop gain) * 1 bw = 0.4-30khz * 2 din audio v 6 = 2.0v (vr = min. time) v 4 = 2.0v (vr = min. time) v in = ?26.0dbv, mic off, * 1 mic off, rg = 600 w , * 2 v in = 52dbv, * 1 v in = 44dbv, mic off, * 2 v in = 52dbv, * 1 rg = 600 w , * 2 v in = ?5.0dbv, v 4 = 9.0v, * 1 thd = 1%, * 1
6 multimedia ics ba7725s / ba7725fs measurement circuit bf bf bf vr vr sw expand 12345 7891011 6 17 12 13 14 15 16 18 19 20 21 22 v4 v6 + + r17 c15 r13 c14 r16 c18 r34 1k c33 r11 c10 r9 c12 r8 + + + compress 0.1 m mic amp in r2 2.2k r3 82k c1 1 m c4 22 m c5 0.1 m c6 0.47 m c32 0.1 m r35 10k dly bf in cmp bf out + c30 2.2 m c20 0.1 m r31 10k r33 1k line out line in c20 0.1 m c19 0.47 m + + v cc 9v fig.1 the above measurement circuit applies to a ba7725s mount- ed to a 22-pin sdip package. a ba7725fs mounted to a 20- pin ssop-a package lacks n.c. pins 3 and 20; other than this difference, the above circuit diagram applies. circuit operation (1) mic amp in / line out gain microphone amplifier gain (determined by r9 and r10) + line amplifier gain (+12db) the audio signal is input via pin 22 (ba7725s) or pin 20 (ba7725fs) and amplified by the internal microphone amplifi- er, whose gain can be set with (attached) r9 and r10. note: microphone amplifier gain must be set above +15db. microphone amplifier frequency characteristic measurement circuit + fig.2 1.5k 12k 22 21 ba7725s v out v in 60 50 40 30 20 10 0 ?10 ?0 ?0 ?40 1m 10m 24681 1 8 6 4 21 8 6 4 2 open loop gain 10k 100k frequency characteristic (hz) voltage (db) microphone amplifier frequency characteristics fig.3 ++ + + 18db + fig.4 2 1 21 22 mic amp in r9 r10 sw line out line in
7 multimedia ics ba7725s / ba7725fs 10 5 100 ?0 0 secondary echo sound source primary echo 0 a tt (db) v 4 = 9.0v loop gain ctrl pin voltage : (v) line output attenuation vs. loop gain control pin voltage line output attenuation : a tt (db) fig.7 0 ?50 100 0510 primary echo sound source a tt (db) echo level ctrl pin voltage : (v) line output attenuation vs. echo level control pin voltage line output attenuation : a tt (db) fig.6 (2) line in / line out gain line amplifier gain is fixed at +18db. + + + + +12db fig.5 2 1 21 22 mic amp in r9 r10 sw line out line in after being amplified by the internal microphone amplifier, the audio signal is log- arithmically compressed by 1 / 2 then input to the tertiary low pass filter, which comprises an internal bf and attached capacitor and resistor. (3) echo level control the dc voltage supplied to pin 4 (ba7725s) or pin 3 (ba7725fs) determines when the microphone switch is turned on and off and controls the echo level. line input and level-controlled microphone input are mixed and output. mode threshold voltage operation l (1.0v max.) only line audio is output. mic off h (2.0v min.) mic on microphone switch control echo level control attenuation of the primary echo signals from sound source can be controlled by changing the dc voltage impressed on pin 4 (ba7725s) or pin 3 (ba7725fs) between 2v and 9v. attenuation of primary echo signals can be controlled by changing the dc voltage impressed on pin 6 (ba7725s) or pin 5 (ba7725fs) .
8 multimedia ics ba7725s / ba7725fs a : echo signal attenuation b : loop signal attenuation c : delay time ccc b b a (db) (t) fig.8 relationship between echo gain and loop gain (4) echo signal frequency characteristicis the figure below shows the attenuation of signals out- put from pin 1 when the audio signal is input to pin 22 (ba7725s) or pin 20 (ba7725fs). (this is the attenua- tion when the input signal is output without being passed through the bu9252s / f, and when the prima- ry and secondary echo signals are passed through an attached low pass filter with the same constant shown in "application example," and then processed by the bu9252s / f delay circuit.) note: these are the values when using the constant shown in "application example." 0 ?0 ?0 ?0 ?40 ?50 100 1k 10k 100k sound source secondary echo signal signal frequency : f (hz) 3pin, 5pin = v cc (vr : max.) echo signal frequency characteristics line output attenuation : a tt (db) fig.9 primary echo signal external dimensions (units: mm) sdip22 ssop-a20 3.95 0.3 0.51min. 19.4 0.3 3.4 0.2 0.5 0.1 6.5 0.3 1 11 12 22 0.3 0.1 0 ~ 15 1.778 7.62 ba7725s ba7725fs 11 10 20 1 0.11 7.8 0.3 5.4 0.2 8.7 0.2 0.15 0.1 0.36 0.1 0.8 1.8 0.1 0.3min. 0.15
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