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 •1)Features Available in compact SZIP and SSOP-A24-pin pack2) 3) 4) 5) 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. ages. High-with standing-voltage head switch (AC with standing voltage: Min. 80VP-P (f = 70kHz) ). Simple, three-mode EQ switch built-in (BA7795LS). Built-in LINE / TUNER selector switch. High-performance low-noise playback amplifier. REC HSW 3 RIPPLE FILTER 5 VCC 7 EQ CTRL 9 PB / TU / EE CTRL 11 ALC LEVEL 13 BIAS 15 EP LP + 1 REC OUT 21 REC EQ 23 – 8dB LINE – 8dB TUNER 19 GND 6 PB NFB 8 PB EQ 10 PB OUT 12 PB LINE IN 14 ALC FILTER 16 LINE IN 18 TUNER IN 20 GND 22 LINE OUT 24 REC / EE CTRL REC – 20dB MUTE EP BF REC NFB 4 SP BIAS PB 17 PB IN ALC + 20dB LINE MUTE CTRL 2 PB REC HEAD EQ REC •Block diagram BA7795LS ∗ The BA7795FS has a different pin layout to the BA7795LS. 1 Video ICs BA7795LS / BA7795FS •Absolute maximum ratings (Ta = 25°C) Parameter Symbol VCC Applied voltage Power dissipation BA7795LS Unit 13 V 400∗1 Pd BA7795FS Limits 800∗2 mW Operating temperature Topr – 10 ~ + 65 °C Storage temperature Tstg – 55 ~ + 125 °C ∗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. •Recommended operating conditions (Ta = 25°C) Parameter Symbol Limits Unit VCC 7.5 ~ 12.5 V Power supply voltage •Pin descriptions BA7795LS Pin No. BA7795FS Pin No. Pin name 1 7 HEAD EQ 2 8 PB IN Playback amplifier input / playback head switch 3 9 REC HSW High-withstanding voltage recording head switch 4 10 GND 5 11 RIPPLE FILTER 6 12 PB NFB 7 13 VCC 8 14 PB EQ 9 15 EQ CTRL 10 16 PB OUT 11 17 PB / TU / EE CTRL 12 18 PB LINE IN Playback line amplifier 13 19 ALC LEVEL ALC level setting 14 20 ALC FILTER ALC filter time constant 15 21 BIAS 16 22 LINE IN 17 23 MUTE CTRL 18 24 TUNER IN Tuner input (REC / EE control) 19 1 REC NFB Recording amplifier feedback 20 2 GND 21 3 REC OUT 22 4 BF OUT Line amplifier output 23 5 REC EQ Recording EQ switch (recording EQ switch 2) 24 6 REC / EE CTRL 2 Function Head resonance capacitor 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) Bias Line input MUTE control GND Recording amplifier output REC / EE control (recording EQ switch 1) Video ICs BA7795LS / BA7795FS •Electrical characteristics (unless otherwise noted, Ta = 25°C, V CC Parameter = 9V, and f = 1kHz) Symbol Min. Typ. Max. Unit Conditions Quiescent current EE IqEE 6.3 8.3 10.8 mA When no signal Quiescent current PB IqPB 6.3 8.3 10.8 mA When no signal Quiescent current REC IqREC 4.9 6.4 8.4 mA When no signal Power supply gain (PB input) GVCP 27.0 28.0 29.0 dB VO = – 8dBV Power supply gain (LINE1, LINE2, TU inputs) GVCL 19.0 20.0 21.0 dB VO = – 8dBV Distortion THDL — 0.1 0.3 % VO = – 8dBV, RL = 4.7kΩ∗1 Maximum output level VOmL 5.0 7.2 — dBV THD = 1%, RL = 4.7kΩ∗1 Output residual noise VNOL — – 81.5 – 75 dBV Rg = 4.7kΩ, DIN AUDIO ALC level VOA – 7.0 – 6.0 – 5.0 dBV VIN = – 23dBV R1 / R2 = 8.2 / 39kΩ THDA — 0.18 0.5 % VIN = – 23dBV, RL = 4.7kΩ∗1 MT — – 82.5 – 72 dB Vo = 0dBV, DIN AUDIO Voltage gain GVCR 19.0 20.0 21.0 dB LINE, TUNER input→REC OUT Distortion THDR — 0.03 0.3 % VO = – 8dBV Maximum output level VOmR 5.5 7.4 — dBV Open loop gain GVOR 65 77 — dB Open loop gain GVOP 62 Input conversion noise VNINP — – 122.5 – 114 Total gain GVCP-L 56 57.5 59 dB PB head switch impedance RPH — 11 20 Ω REC head switch impedance RRH — 11 20 Ω BVRHAC 80 100 — VP-P 〈Line amplifier〉 ALC distortion Mute attenuation ratio 〈Recording amplifier〉 VO = – 8dBV, RL = 4.7kΩ∗1 THD = 1%, RL = 4.7kΩ∗1 〈Playback preamplifier〉 68 — dB dBV Rg = 680Ω, DIN AUDIO PB IN →BF OUT 〈Head switch〉 REC head switch AC withstanding voltage f = 70kHz ∗1 Measured at BW = 400Hz to 30kHz. 3 Video ICs BA7795LS / BA7795FS •Input / output circuits 10kΩ EQ CTRL 56kΩ PB / TU / EE CTRL REC / EE CTRL 56kΩ MUTE CTRL 56kΩ REC Fig. 1 4 PB HSW Video ICs BA7795LS / BA7795FS •Measurement circuit 680 3.3µ + EP LP + 1 REC BA7795LS PB IN 68k 1k 2 3 5 + 22µ 330 22µ 4 330k 12k PB 7 0.01µ 6 + 33µ + VCC ON: GVOPB REC AC BIAS IN PB / TU / EE CTRL 11 SP 9 8.2k 8 EQ CTRL 10 4.7k R1 13 BIAS 17 – 8dB TUNER 1.5k 18 4.7k 4.7k LINE IN TUNER IN 20 21 4.7k REC 22 – 20dB RL LINE OUT 10µ MUTE 23 EP 4.7k + BF 10µ + REC OUT 15k 100µ + 19 0.1µ LINE ON: ALC OFF 16 0.1µ – 8dB LINE ALC + 28dB ON: GVEREC 2.2M 14 15 MUTE CTRL 47µ + PB 12 0.1µ 4.7k R2 24 REC / EE CTRL Units: R [Ω] C [F] ∗ The BA7795FS has a different pin layout to the BA7795LS. Fig. 2 5 Video ICs BA7795LS / BA7795FS operation •(1)Circuit EE oparation (2) Recoeding In recording mode, the recording amplifier directly connected to the line amplifier operates. The PB HEAD switch in the playback equalizer amplifier 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 characteristic to suit the tape speed by switchig the control signal to EQ CTRL. The recording amplifier gain and equalizer characteristics are set externally. 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 connects the output buffer will go off, but the ALC loop will not be cut. EP LP + 3.3µ + 1 REC Signal flow for EE and recording operation 2 3 33µ REC 330 5 6 7 PB + + VCC 22µ 4 + 22µ 0.01µ 330k 8 EQ CTRL 12k 9 8.2k 4.7k 4.7k 10 PB / TU / EE CTRL 11 0.1µ 12 PB + 39k 13 8.2k BIAS 14 2.2M ALC – 8dB 15 LINE 17 – 8dB 1.5k 19 15k TUNER IN 22 MUTE – 20dB RL LINE OUT 10µ REC / EE CTRL 24 EP Units: R [Ω ] C [F] BA7795LS ∗ The BA7795FS has a different pin layout to the BA7795LS. Fig. 3 Signal flow for EE / recording 6 18 REC BF + REC + B LINE IN 20 21 23 BIAS OSC 16 + 28dB + MUTE CTRL 47µ 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 characteristics 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 characteristic 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. REC Signal flow for playback operation 1 3.3µ EP LP + REC + 2 4 3 22µ + 33µ 22µ 5 + VCC 330k + 6 PB 7 0.01µ 330k EQ CTRL 9 PB / TU / EE CTRL 11 SP 8 12k 8.2k 10 4.7k 0.1µ 12 PB 39k + 13 8.2k 2.2M LINE 17 – 8dB ALC + 28dB MUTE CTRL LINE IN 16 – 8dB 0.1µ 1.5k 19 15k + 47µ 14 BIAS 15 4.7k TUNER IN 18 0.1µ 20 4.7k REC 21 – 20dB 22 MUTE 23 EP BF 10µ + LINE OUT 10µ REC / EE CTRL 24 BIAS OSC REC + B BA7795LS Units: R [Ω] C [F] ∗ The BA7795FS has a different pin layout to the BA7795LS. Fig. 4 Signal flow for playback 7 Video ICs BA7795LS / BA7795FS mode table •(1)Control REC / EE CTRL, PB / TU / EE CTRL Control pins Function Mode REC / EE PB / TU / EE L L L M TUNER L H PB LINE Mode PB HSW REC HSW LINE SW REC AMP OFF ON LINE OFF OFF ON TUNER OFF OFF ON PB OFF H L LINE REC ON OFF LINE ON H M TUNER REC ON OFF TUNER ON H H inhibit — — — — If REC / EE CTRL is set to "M", the REC pause state is possible (REC head switch: open, REC amplifier: off). (2) MUTE CTRL Control pins MUTE Function Mode LINE SW H MUTE OPEN L MUTE CLOSE (3) EQ CTRL Control pins Mode Function EQ 2 MODE 3 MODE HEAD EQ SW PB EQ SW L SP SP OFF CLOSE OFF M — LP ON OPEN OFF H EP EP ON OPEN ON The L, M and H thresholds are: L to M: 1.7V, L to H: 2.5V, and M to H: 3.3V. 8 REC EQ SW Video ICs BA7795LS / BA7795FS REC 3.3µ LP 2 REC + + 1 EP •Application example (BA7795LS) 4 3 22µ + 33µ 330 5 22µ + + VCC 7 EQ CTRL 9 PB 6 0.01µ 330k SP 8 12k 8.2k 4.7k 4.7k 10 PB / TU / EE CTRL 11 0.1µ 12 PB R1 + 13 R2 14 BIAS 2.2M ALC + 28dB LINE – 8dB TUNER 17 1.5k 19 15k 0.1µ 16 LINE IN 0.1µ 18 TUNER IN 20 RL REC – 20dB 22 MUTE 23 EP BF + 21 + MUTE CTRL – 8dB LINE 15 47µ LINE OUT 10µ REC / EE CTRL 24 BIAS OSC Units: R [Ω] C [F] REC + B ∗ The BA7795FS has a different pin layout to the BA7795LS. Fig. 5 9 Video ICs BA7795LS / BA7795FS notes •(1)Operation 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: (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 audible, particularly when the power is switched on. VCC 1 VOA = 2 1 = 2 R1 VCC – 0.7 • • R1 + R2 2 R1 • VBIAS • R1 + R2 (H) (H) 2sec or more MUTE CTRL LINE OUT Fig. 7 If the ALC level setting is too low, level variation will increase compared to that of the standerd level (VOA = – 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 (VCC) as shown in the formula above. Use care when setting it. Also, be certain to apply the mute signal when switching 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. VBIAS = VCC – 0.7 2 R1 VBIAS R1 + R2 ALC LEVEL Fig. 6 10 BIAS (4) Line output The line output can drive a load resistance of up to 2kΩ. 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 connected to a shielded cable, or line cable, connect a resistor of about 1kΩ in series with the output so that the capacitive load is not directly coupled to the IC output terminal. Video ICs BA7795LS / BA7795FS •Electrical characteristic curves 10 40 20 OUTPUT LEVEL: VOA (dBV) 20 10 0 100 1k 10k 100k 0 13 R1 = 18kΩ R1 5.6kΩ R1 = 39kΩ – 10 – 20 – 30 – 40 1M Fig. 8 Gain vs. frequency (PB amplifier) – 30 – 10 – 20 0 PB 2 330 22µ ∗ BA7795LS EP (SW: OFF) 40 SP (SW: ON) 20 100 1k 10k 100k 1M 10µ + – 20 RL LINE 200 500 1k 2k 5k 10k Fig. 9 Line amplifier ALC input / output characteristics Fig. 10 Line amplifier load drive characteristics – 70 – 20 – 30 LINE VCC = 9V ALC; OFF DIN AUDIO – 40 – 50 – 60 – 70 TU→LINE PB→LINE – 80 MUTE – 90 – 100 0 – 10 OUTPUT IMPEDANCE RL (Ω) – 10 0.01µ + 60 VCC = 9V (ALC; OFF) f = 1kHz THD = 1% (0.4 ~ 30kHz) 0 SW 8 10 6 8.2k 330k 12k OUTPUT LEVEL: VO (dBV) GVO 80 0 100 10 10 100 10 INPUT LEVEL: VIN (dBV) FREQUENCY: f (Hz) GAIN: GVOP – GVC (dB) R1 = 12kΩ 15 10M FREQUENCY: f (Hz) Fig. 11 Playback amplifier frequency characteristics – 110 10 100 1k 10k 100k FREQUENCY: f (Hz) Fig. 12 Line amplifier crosstalk OUTPUT NOISE LEVEL: VON (dBV) GAIN: GVCLT (dB) 30 MAXIMUM OUTPUT LEVEL: VOmL (dBV) VCC = 9V f = 1kHz VCC = 9V ALC; OFF – 80 – 90 – 100 DIN AUDIO VCC = 9V CIN = 4.7µF 100 200 500 1k 2k 5k 10k INPUT IMPEDANCE: Rg (Ω) Fig. 13 Playback amplifier output noise characteristics 11 Video ICs BA7795LS / BA7795FS •External dimensions (Units: mm) BA7795LS BA7795FS 2.8 ± 0.2 0.5 ± 0.1 0.1 0.3 + – 0.05 2.54 ± 0.25 1 23 24 13 1 12 5.4 ± 0.2 7.8 ± 0.3 1.8 ± 0.1 0.889 0.11 2.0Min. 5.8 ± 0.2 9.9 ± 0.5 10.0 ± 0.2 0.8 0.36 ± 0.1 0.15 ± 0.1 21.8 ± 0.2 0.3Min. 0.15 2 24 SZIP24 12 SSOP-A24