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1 video ics vcr standard audio signal processor ba7795ls / ba7795fs the ba7795ls and ba7795fs are standard audio signal processor ics. they contain a playback preamplifier, line amplifier, recoeding amplifier, alc circuit, eq switch circuit and high-voltage head switch, and provide all of the functions required for normal-audio signal processing on a single ic with a minimum number of external components required. applications video cassette recorders and tape decks features 1) available in compact szip and ssop-a24-pin pack- ages. 2) high-with standing-voltage head switch (ac with standing voltage: min. 80v p-p (f = 70khz) ). 3) simple, three-mode eq switch built-in (ba7795ls). 4) built-in line / tuner selector switch. 5) high-performance low-noise playback amplifier. input conversion noise figure ?122dbv (typ. rg = 680, din audio). 6) alc level can be varied. 7) alc loop external mute eliminates audible noise at power on, and alc attack noise. 8) signal processing circuit can be constructed with the addition of just a few external components. block diagram 1 3 5 7 9 11 13 15 17 19 21 23 24 22 20 18 16 14 12 10 8 6 4 2 pb in gnd pb nfb pb eq pb out pb line in alc filter line in tuner in gnd line out rec / ee ctrl head eq rec hsw ripple filter v cc eq ctrl pb / tu / ee ctrl bias mute ctrl rec nfb alc level rec out rec eq alc ?20db pb mute bf rec ?8db tuner ?8db line line + 20db bias sp pb rec ep lp + rec ep ba7795ls * the ba7795fs has a different pin layout to the ba7795ls.
2 video ics ba7795ls / ba7795fs pin descriptions ba7795ls pin no. ba7795fs pin no. pin name function 17 head eq 28 pb in 39 rec hsw 410 gnd 511 ripple filter 612 pb nfb 713 v cc 814 pb eq 915 eq ctrl 10 16 pb out 11 17 pb / tu / ee ctrl 12 18 pb line in 13 19 alc level 14 20 alc filter 15 21 bias 16 22 line in 17 23 mute ctrl 18 24 tuner in 19 1 rec nfb 20 2 gnd 21 3 rec out 22 4 bf out 23 5 rec eq 24 6 rec / ee ctrl head resonance capacitor switch playback amplifier input / playback head switch high-withstanding voltage recording head switch gnd (playback amplifier) ripple filter playback amplifier feedback power supply playback eq switch eq control playback amplifier output pb / tu / ee control (pb / ee control) playback line amplifier alc level setting alc filter time constant bias line input mute control tuner input (rec / ee control) recording amplifier feedback gnd recording amplifier output line amplifier output recording eq switch (recording eq switch 2) rec / ee control (recording eq switch 1) absolute maximum ratings (ta = 25?) recommended operating conditions (ta = 25?) parameter symbol limits unit v cc 13 v ba7795ls pd mw ba7795fs topr c tstg c 400 * 1 800 * 2 ? 10 ~ + 65 ? 55 ~ + 125 * 1 reduced by 4.0mw for each increase in ta of 1 c over 25 c. * 2 reduced by 8.0mw for each increase in ta of 1 c over 25 c. applied voltage power dissipation operating temperature storage temperature parameter symbol limits unit 7.5 ~ 12.5 v v cc power supply voltage
3 video ics ba7795ls / ba7795fs electrical characteristics (unless otherwise noted, ta = 25?, v cc = 9v, and f = 1khz) parameter symbol min. typ. max. unit conditions i qee 6.3 8.3 10.8 ma i qpb 6.3 8.3 10.8 ma i qrec 4.9 6.4 8.4 ma g vcp 27.0 28.0 29.0 db v o = ? 8dbv g vcl 19.0 20.0 21.0 db v o = ? 8dbv thd l 0.1 0.3 % v o = ? 8dbv, r l = 4.7k w * 1 v oml 5.0 7.2 dbv thd = 1 % , r l = 4.7k w * 1 v nol ? 81.5 ? 75 dbv r g = 4.7k w , din audio v oa ? 7.0 ? 6.0 ? 5.0 dbv r 1 / r 2 = 8.2 / 39k w v in = ? 23dbv thd a 0.18 0.5 % v in = ? 23dbv, r l = 4.7k w * 1 mt ? 82.5 ? 72 db vo = 0dbv, din audio g vcr 19.0 20.0 21.0 db thd r 0.03 0.3 % v o = ? 8dbv v omr 5.5 7.4 dbv v o = ? 8dbv, r l = 4.7k w * 1 g vor 65 77 db thd = 1 % , r l = 4.7k w * 1 g vop 62 68 db v ninp ? 122.5 ? 114 dbv r g = 680 w , din audio g vcp-l 56 57.5 59 db pb in ? bf out r ph 11 20 w r rh 11 20 w bv rhac 80 100 v p-p f = 70khz line, tuner input ? rec out * 1 measured at bw = 400hz to 30khz. when no signal when no signal when no signal quiescent current ee quiescent current pb quiescent current rec line amplifier ? power supply gain (pb input) power supply gain (line1, line2, tu inputs) distortion maximum output level output residual noise alc level alc distortion mute attenuation ratio recording amplifier ? voltage gain distortion maximum output level open loop gain playback preamplifier ? open loop gain input conversion noise total gain head switch ? pb head switch impedance rec head switch impedance rec head switch ac withstanding voltage
4 video ics ba7795ls / ba7795fs input / output circuits 10k w eq ctrl 56k w pb / tu / ee ctrl mute ctrl 56k w rec / ee ctrl 56k w rec pb hsw fig. 1
5 video ics ba7795ls / ba7795fs units: r [ w ] 1 3 5 7 9 11 13 15 17 19 21 23 24 22 20 18 16 14 12 10 8 6 4 2 ?20db pb mute bf rec ?8db tuner ?8db line line + 28db bias sp pb rec ep lp + rec ac bias in 1k 22 m 33 m v cc eq ctrl pb / tu / ee ctrl r2 r1 mute ctrl 15k 100 m 10 m on: g ve rec rec out 4.7k 68k 680 3.3 m 330 on: g vopb 22 m 330k 12k 8.2k 0.01 m 4.7k 4.7k 47 m 0.1 m 2.2m on: alc off line in 4.7k 4.7k 4.7k 0.1 m 0.1 m 10 m rl tuner in line out rec / ee ctrl ep pb in 1.5k alc fig. 2 * the ba7795fs has a different pin layout to the ba7795ls. c [f] + + + + + + + + measurement circuit ba7795ls
6 video ics ba7795ls / ba7795fs circuit operation (1) ee oparation the input switch is used to select the audio signal input source (line or tuer). this signal is amplified by the line amplifier (voltage gain: 20db at 1khz). the alc circuit controls the line amplifier output level. the alc level is set externally. if mute mode is set in this state, the switch that con- nects the output buffer will go off, but the alc loop will not be cut. (2) recoeding in recording mode, the recording amplifier directly con- nected to the line amplifier operates. the pb head switch in the playback equalizer amplifi- er block switches on, and the signal is not input to the playback equalizer amplifier. the line amplifier output is attenuated by 20db before it is input to the recording amplifier, so if the feedback components are chosen to given a gain of 20db, the same rec out output level as the line amplifier can be obtained. it is also possible to switch the rec equalizer charac- teristic to suit the tape speed by switchig the control signal to eq ctrl. the recording amplifier gain and equalizer characteristics are set externally. signal flow for ee and recording operation c [f] units: r [ w ] 1 3 5 7 9 11 13 15 17 19 21 23 24 22 20 18 16 14 12 10 8 6 4 2 ?20db pb mute bf rec ?8db ?8db line + 28db bias pb rec ep lp + rec ep 22 m 33 m v cc eq ctrl pb / tu / ee ctrl 39k 8.2k mute ctrl 1.5k 15k bias osc rec + b 3.3 m 330 22 m 0.01 m 330k 12k 8.2k 4.7k 4.7k 0.1 m 47 m 2.2m line in tuner in r l line out 10 m rec / ee ctrl ba7795ls alc * the ba7795fs has a different pin layout to the ba7795ls. fig. 3 signal flow for ee / recording + + + + + + +
7 video ics ba7795ls / ba7795fs (3) playback operation the signal applied to pb in is amplified by playback equalizer amplifier. at this time, the rec head switch is switched on by a control signal to rec / ee, and the potential on one side of the head is fixed at gnd . the playback equalizer amplifier gain and equalizer charac- teristics are set externally. the playback level is set by the resistor divider between pb out and the playback line input, the signal to the playback line input passes though the input switch, is amplified by 20db in the line amplifier, and is output to the output buffer (the voltage gain is different to that for the line input and tuner input). it is possible to switch between the input block head equalizer resonance point and playback equalizer char- acteristic using the eq ctrl control signal. the line output can be stopped by setting muting mode on using the mute ctrl signal. the alc circuit and recording amplifier are stopped in playback mode. signal flow for playback operation 1 3 5 7 9 11 13 15 17 19 21 23 2 4 6 8 10 12 14 16 18 20 22 24 + + + + + rec + b 22 m 33 m 22 m 10 m 0.1 m 47 m 0.01 m 39k alc line 3.3 m 330k 330k 12k 8.2k 4.7k 4.7k 0.1 m v cc ep rec bias ? 20db mute bf ? 8db ? 8db pb pb sp rec 2.2m 4.7k 8.2k 15k 1.5k 10 m ep lp + rec + 28db 0.1 m rec / ee ctrl eq ctrl pb / tu / ee ctrl mute ctrl bias osc line in tuner in line out ba7795ls c [f] units: r [ w ] * the ba7795fs has a different pin layout to the ba7795ls. fig. 4 signal flow for playback + +
8 video ics ba7795ls / ba7795fs control mode table (1) rec / ee ctrl, pb / tu / ee ctrl l l off on line off l m tuner off on tuner off l h pb off on pb off h l on off line on h m on off on h h inhibit tuner line rec tuner rec rec / ee pb / tu / ee pb hsw rec hsw line sw rec amp mode control pins function if rec / ee ctrl is set to "m", the rec pause state is possible (rec head switch: open, rec amplifier: off). mode line (2) mute ctrl mute h mute open l mute close line sw function mode control pins (3) eq ctrl e q l sp sp off close off m lp on open off h ep ep on open on 2 mode 3 mode head eq sw pb eq sw rec eq sw control pins mode function the l, m and h thresholds are: l to m: 1.7v, l to h: 2.5v, and m to h: 3.3v.
9 video ics ba7795ls / ba7795fs application example (ba7795ls) 1 3 5 7 9 11 13 15 17 19 21 23 2 4 6 8 10 12 14 16 18 20 22 24 rec + b 22 m 33 m 22 m 10 m 47 m 0.01 m alc line 3.3 m 330k 12k 8.2k 4.7k 4.7k 0.1 m v cc ep rec bias ? 20db mute bf ? 8db pb pb sp rec 2.2m 15k ep lp + rec + 28db 0.1 m r 1 r 2 1.5k line ? 8db tuner r l 330 eq ctrl mute ctrl line out pb / tu / ee ctrl bias osc rec / ee ctrl 0.1 m line in tuner in fig. 5 * the ba7795fs has a different pin layout to the ba7795ls. units: r [ w ] c [f] + + + + + + +
10 video ics ba7795ls / ba7795fs operation notes (1) alc level set the alc level in the range ?8dbv to 0dbv by selecting the values of resistors r1 and r2 connected between bias, alc level and gnd. the formula for approximating the value of this resistor is as follows: if the alc level setting is too low, level variation will increase compared to that of the standerd level (v oa = ?6dbv), and conversely, if the level is too high, the level variation will decrease, but distortion will increase.there is almost no temperature characteristic, but the alc level does vary with supply voltage (v cc ) as shown in the formula above. use care when setting it. (2) mute signal apply the mute signal shown below at power on and off. if the muting time is short, a pop sound will be audi- ble, particularly when the power is switched on. also, be certain to apply the mute signal when switch- ing between pb / line / tu. in the case of line / tu switching, it is possible to suppress switching noise by applying a time constant to the signal, in which case it is not necessary to apply the mute signal. (3) recording control do not switch the pb and rec modes on togther. this will cause faulty operation. (4) line output the line output can drive a load resistance of up to 2k w . depending on the type of load, it can cause local oscillation (eg. large capacitive loads that draw large current), so caution is required. in particular, when there is a possibility that the line output will be connect- ed to a shielded cable, or line cable, connect a resistor of about 1k w in series with the output so that the capacitive load is not directly coupled to the ic output terminal. 2sec or more (h) v cc mute ctrl line out (h) fig. 7 2 v cc 0.7 r 1 r 1 + r 2 ?v bias v oa = = ? 1 r 1 r 1 + r 2 2 1 2 ? 2 v cc ? 0.7 r 1 r 1 + r 2 v bias v bias = bias alc level fig. 6
11 video ics ba7795ls / ba7795fs electrical characteristic curves v cc = 9v alc; off 40 30 20 10 0 100 1k 10k 100k 1m frequency: f (hz) gain: g vclt (db) fig. 8 gain vs. frequency (pb amplifier) ?20 v cc = 9v f = 1khz 13 15 r 1 5.6k w r 1 = 18k w r 1 = 12k w r 1 = 39k w 10 0 ?10 ?20 ?30 ?40 ?30 ?10 0 10 input level: v in (dbv) output level: v oa (dbv) fig. 9 line amplifier alc input / output characteristics v cc = 9v (alc; off) f = 1khz thd = 1% (0.4 ~ 30khz) + 10 m line r l 100 200 500 1k 2k 5k 10k ?20 ?10 0 10 20 output impedance r l ( w) maximum output level: v oml (dbv) fig. 10 line amplifier load drive characteristics pb sw 8.2k 330k 330 + 0.01 m 22 m 2 6 8 10 12k 100 1k 10k 100k 1m 10m 0 20 40 60 80 100 frequency: f (hz) gain: gv op ?g vc (db) g vo sp (sw: on) ep (sw: off) * ba7795ls fig. 11 playback amplifier frequency characteristics v cc = 9v alc; off din audio line tu ? line pb ? line 10 100 1k 10k 100k 10 0 ? 20 ? 10 ? 30 ? 40 ? 50 ? 60 ? 70 ? 80 ? 90 ? 100 ? 110 output level: v o (dbv) frequency: f (hz) mute fig. 12 line amplifier crosstalk din audio v cc = 9v c in = 4.7 m f 100 200 500 1k 2k 5k 10k ? 70 ? 80 ? 90 ? 100 input impedance: rg ( w ) output noise level: v on (dbv) fig. 13 playback amplifier output noise characteristics
12 video ics ba7795ls / ba7795fs szip24 ba7795ls ba7795fs ssop-a24 5.8 0.2 9.9 0.5 0.889 1 2 23 24 0.5 0.1 + 0.1 ? 0.05 2.54 0.25 0.3 2.0min. 21.8 0.2 2.8 0.2 0.15 0.3min. 7.8 0.3 5.4 0.2 1.8 0.1 0.11 1 24 0.36 0.1 10.0 0.2 12 13 0.8 0.15 0.1 external dimensions (units: mm)

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