Video ICs VCR Hi-Fi audio signal REC / PB amplifier BA7746S / BA7746FS The BA7746S and BA7746FS contains the recording and playback amplifiers required for Hi-Fi VCR signal processing. The recording system uses a constant-current amplifier with AGC to eliminate the need to adjust the recording current, and ensure stable operation as the head wears. The IC also features REC MUTE and OVER REC functions. The playback system has a high-gain preamplifier, a low- offset head switch, VCA, and an EP-gain amplifier. In addition, all functions operate off a single 5V supply, and a H / L control system eliminates the need for special power supplies for the recording and playback systems. The IC has low power consumpution, and comes in a compact 32-pin SSOP-A package that requires little area on the PCB. It will improve the reliability and performance of your designs while reducing external component requirements. Applications •VCRs •1)Features The low-noise playback amplifier has a total gain of 2) 3) 4) 5) 6) 79dB (Typ.). Designed for VHS-band operation with low external parts count. It has two built-in circuits for Hi-Fi VCR operation. The circuit has been designed to suppress headswitching noise. Built-in EP / SP gain switching function that boosts the playback gain by 5dB. Built-in VCA for easy playback output adjustment. High-output recording amplifier for audio FM recording. Constant-current drive povides stable recording characteristics when the load (head impedance) is fluctuating. 7) Built-in recording level AGC eliminates the need to adjust recording current. 8) Built-in low-pass filter limits the input bandwidth of the recording amplifier. 9) Built-in OVER REC recording current amplifier function and REC MUTE function that stops recording output. 10) Low power consumption. Operates off a single 5V power supply. 11) Record / playback switching can be done directly via the system controller, and consumes littele power. 12) Possible to construct a high-performance audio system by pairing this chip with a Hi-Fi-audio signal processing IC. •Absolute maximum ratings (Ta = 25°C) Parameter Power supply voltage Power dissipation BA7746S BA7746FS Symbol Limits Unit VCC 7.0 V Pd 1050∗1 mW 800∗2 mW Operating temperature Topr – 10 ~ + 70 °C Storage temperature Tstg – 55 ~ + 125 °C ∗1 When mounted on a 90mm × 50mm × 1.6mm glass epoxy board, reduced by 10.5mW for each increase in Ta of 1°C over 25°C. ∗2 When mounted on a 90mm × 50mm × 1.6mm glass epoxy board, reduced by 8mW for each increase in Ta of 1°C over 25°C. 1 Video ICs BA7746S / BA7746FS •Recommended operating conditions (Ta = 25°C) Parameter Operating voltage Symbol Min. Typ. Max. Unit VCCS 4.5 5.0 5.5 V REC CURRENT SENSE 14 REC OUT 15 MAIN GND 16 12 REC / PB CTRL 11 REC NF AGC REC 13 10 REC MIX IN PRE IN ch1 18 PRE GND 19 PRE IN ch2 20 PRE AC – FB ch2 21 N.C. 22 REC + B ch2 23 REC + B ch1 24 VCA SW PRE 9 OVER REC CTRL 8 REC MUTE CTRL 7 VCC 6 VCA CTRL (PRE MUTE) 5 PRE OUT 4 EP / SP CTRL 3 HSWP IN 2 REC TC 1 VCC REC + B R 2 TC ch1 R ch2 N.C. ch2 PRE EP 17 ch1 PRE AC – FB ch1 PB / REC P REC AGC FILTER P/R •Block diagram Video ICs BA7746S / BA7746FS •Pin descriptions Pin No. Pin name, function and remarks Voltage Circuit diagram VCC — 1 〈VCC REC + B〉 • Power supply for REC + B. • Connect to VCC (pin 7). 2 〈REC TC〉 • REC + B time constant. • Use to adjust the REC + B rise time using the C value. The value of the built-in resistor is 20kΩ. • The effect of current spikes when recording is started is reduced 3 〈HSWP IN〉 • Pulse input for head switching. • ch1: H, ch2: L — 4 〈EP / SP CTRL〉 • EP / SP mode control. • In EP mode, the playback amplifier gain is set to + 5dB (Typ.). • EP: H, SP: L • Do not leave open circuit — REC: 0.9V PB: 0V REC 20k 24k 40k EP 5 〈PRE OUT〉 • Playback amplifier output. • Open emitter output. • When there is a chance of oscillation due to capacitive load, reduce the output current, or connect a resistor in series (approx. 390Ω). • Avoid capacitive coupling with the playback input 6 〈VCA CTRL (PRE MUTE)〉 • VCA control. • When the terminal is open (a C is required), the playback amplifier gain is set to the Typ. value. • The PRE MUTE function is made possible by connection of a mute H signal to this through a diode SP REC: 3.6V PB: 1.9V (RL: 1.8kΩ) 30k REC: 2.0V PB: 2.0V 580 20k MUTE H 3 Video ICs Pin No. BA7746S / BA7746FS Pin name, function and remarks 7 〈VCC〉 • Power supply for anything other than REC + B. 8 〈REC MUTE CTRL〉 • REC MUTE control. • In REC MUTE mode, the recording amplifier output is stopped. • REC: L, REC MUTE: H. • Do not leave open circuit. Voltage Circuit diagram VCC — — 30k MUTE 9 〈OVER REC CTRL〉 • OVER REC control. • In OVER REC mode, the recording current is set to + 2dB (Typ.). • Do not leave open circuit. REC — 30k OVER NORMAL 10 11 12 4 〈REC MIX IN〉 • Recording amplifier input. REC: 2.9V PB: 2.9V 〈REC NF〉 • Recording amplifier feedback. • Connect the GND of a decoupling capacitor to main GND (pin 16) to improve common-mode distortion. REC: 1.4V PB: 0.5V 〈REC / PB CTRL〉 • REC / PB control pin. • Use of an RC circuit time constant to slow the rise of the control signal reduces noise spikes during switching. • Do not leave open circuit. 10k 10k 10.2k 240 1.04k — 30k Video ICs Pin No. BA7746S / BA7746FS Pin name, function and remarks Voltage 〈REC AGC FILTER〉 • REC AGC filter. • The attack characteristics of the recording amplifier can be adjusted using the CR circuit. • Reduce the CR circuit GND-side impedance to improve the common-mode distortion. REC: 0V PB: 0V 〈REC CURRENT SENSE〉 • Terminal for monitoring the recording current. • Open emitter output. • The REC AGC output current can be adjusted with the R value. e.g. 12Ω...48.2mAP-P, 15Ω...38.6mAP-P REC: 0.58V PB: 0V 15 〈REC OUT〉 • Recording amplifier output and head switch. • Open collector output. • The head switch turns on and off in accordance with the REC / PB control signal REC: 4.1V PB: 0V 16 〈MAIN GND〉 • Earth for circuits other than the preamplifier. • Reference potential for the IC 17 〈PRE AC-FB ch1〉 • AC feedback terminal for the playback amplifier (ch1). • The high-frequency characteristics of the playback amplifier can be adjusted with the R value 13 14 Circuit diagram 2k 2k 15 14 GND — REC: 0V PB: 0.8V 4k 17 18 〈PRE IN ch1〉 • Input terminal for the playback amplifier (ch1). • The low-frequency cutoff characteristics can be adjusted with the value of the input coupling capacitor. • The frequency characteristics can be adjusted so that it is flat with the L value of the rotary transformer, and the external capacitor C (100pF etc.). 13k 18 REC: 0V PB: 0.7V 5 Video ICs Pin No. BA7746S / BA7746FS Pin name, function and remarks 19 〈PRE GND〉 • GND for the HEAD AMP. • Use this terminal for the pin 17 to pin 21 GND connections to improve the noise characteristics. • Connect this pin to the main GND (pin 16). 20 〈PRE IN ch2〉 • Inputl for the playback amplifier (ch2). The low-frequency cutoff characteristics can be adjusted with the value of the input coupling capacitor. • The frequency characteristics can be adjusted so that it is flat with the L value of the rotary transformer, and the external capacitor C (100pF etc.). Voltage Circuit diagram GND — REC: 0V PB: 0.7V 4k 21 13k 20 21 〈PRE AC-FB ch2〉 • AC feedback for the playback amplifier (ch2). • The high-frequency characteristics of the playback amplifier can be adjusted with the R value. REC: 0V PB: 0.8V 22 〈N.C.〉 • Unused. • Connect to 〈MAIN GND〉 to improve the interchannel matching. 23 〈REC + B ch2〉 • REC + B (ch2). • Open emitter output circuit. • Turns on and off in accordance with the REC / PB control signal. REC: 4.1V PB: 0V 24 〈REC + B ch1〉 • REC + B (ch1). • Open emitter output circuit. • Turns on and off in accordance with the REC / PB control signal. REC: 4.1V PB: 0V — ∗ The values given above are design values, they are not ratings and are not guaranteed. 6 — Video ICs BA7746S / BA7746FS Electrical characteristics •Recording mode (pin 12→ "H") (unless otherwise noted, Ta = 25°C, V CC Parameter Quiescent current Symbol Iq (REC) Min. Typ. Max. Unit — 66 90 mA = 5.0V, and f = 1.7MHz) Conditions No signal, pin 1 + pin 7, inflow current Output current AGC level IOAR 44.2 48.2 52.2 mAP-P Output current AGC level ∆IOAR 10 13 — dB ∆AGC 10pin 93.0dBµIN, 14pin OUT < 0.8dB, 14pin OUT Cross modulation distortion 0.4MHz component CMD04 — – 50 – 40 dB 10pin MIXIN∗, 14pin OUT (0.4MHz - 1.3MHz) Cross modulation distortion 0.9MHz component CMD09 — – 55 – 40 dB 10pin MIXIN∗, 14pin OUT (0.9MHz - 1.3MHz) OVER REC holding voltage V9L 0.0 — 2.2 V OVER REC holding voltage V9H 3.5 — VCC V IOR.OV 1.4 1.9 2.4 dB 10pin 93.0dBµIN, 9pin: “H” REC MUTE holding voltage V8L 0.0 — 2.2 V 8pin DC, When MUTE OFF REC MUTE holding voltage V8H 3.5 — VCC V 8pin DC, When MUTE ON IOR.MU — – 50 – 40 dB 10pin 93.0dBµIN, 8pin: “H” Current emphasis OVER Mute attenuation 9pin DC, When NORMAL REC 9pin DC, When OVER REC ∗ f = 1.3MHz (87.0dBµ) + 1.7MHz (95.0dBµ) (MIX) Playback mode (pin 12→ "L") (unless otherwise noted, Ta = 25°C, VCC = 5.0V, and f = 1.5MHz) Symbol Min. Typ. Max. Unit Supply current Parameter Iq 〈PB〉 — 19 31 mA Inflow current to pin 7 when no signal. Conditions Voltage gain CH1 GVP1 75 79 83 dB 18pin, 20.5dBµIN, 5pin OUT, 3pin: “H” Voltage gain CH2 GVP2 75 79 83 dB 20pin, 20.5dBµIN, 5pin OUT, 3pin: “L” Voltage gain differential ∆GVP – 2.0 0 2.0 dB 18pin, 20pin, 20.5dBµ, ∆5pin OUT CH1 to CH2 crosstalk CT1→2 — – 45 – 35 dB 18pin 31.0dBµ, 20pin 0 IN, 3pin: “H”→ “L”, ∆5pin OUT CH2 to CH1 crosstalk CT2→1 — – 45 – 35 dB 18pin 0, 20pin 31.0dBµIN, 3pin: “L”→ “H”, ∆5pin OUT CH1 frequency characteristic fP1 0 – 2.4 –5 dB 18pin 20.5dBµIN, 3pin: “H” f = 2.2MHz / 1.0MHz, ∆5pin OUT CH2 frequency characteristic fP2 0 – 2.4 –5 dB 20pin 20.5dBµ IN, 3pin: “L” f = 2.2MHz / 1.0MHz, ∆5pin OUT Gain adjustment headroom – ∆GVCA — – 50 – 35 dB 6pin 3.2V, ∆5pin OUT Gain adjustment headroom + ∆GVCA 4 6 — dB 6pin 0.8V, ∆5pin OUT Maximum output voltage VOMP 2.0 2.6 — VP-P Pin 18 and 20 IN, pin 5 OUT 3rd-harmonic distortion, when-30dB. CH1 input conversion noise VNP1 — 0.4 1.0 µVrms Input conversion for pin 18: 0.01µ F + 10Ω at GND Pin 3: “H”, pin 5 OUT. CH2 input conversion noise VNP2 — 0.4 1.0 µVrms Input conversion for pin 20: 0.01µF + 10Ω at GND Pin 3: “L”, pin 5 OUT. 7 Video ICs BA7746S / BA7746FS Electrical characteristics •Playback mode (pin 12→ "L") (unless otherwise noted, Ta = 25°C, V CC Parameter = 5.0V, and f = 1.5MHz) Symbol Min. Typ. Max. Unit Head switching voltage VHS2 0.0 — 2.2 V Pin 3 DC when ch2 operating Head switching voltage VHS1 2.8 — VCC V Pin 3 DC when ch1 operating – 20 0 20 mV ∆VODC Output DC offset Conditions 18, 20pin 0 IN, 3pin “H”→ “L” ∆5pin OUT PB holding voltage V12L 0.0 — 1.0 V Pin 12 DC for PB mode REC holding voltage V12H 3.5 — VCC V Pin 12 DC for REC mode Head switch ON resistance RSWP — 5 10 Ω Pin 15 ON resistance SP holding voltage V4L 0.0 — 2.2 V Pin 4 DC for SP mode EP holding voltage V4H 3.5 — VCC V Pin 4 DC for EP mode Gain emphasis EP GVP.EP 4.0 5.0 6.0 dB 18, 20pin 20.5dBµIN, 4pin: “H”, 5pin OUT 1k 1k 100p 12µ CURRENT SENSE PRE IN ch1 PRE IN ch2 •Measurement circuit 12µ 560 100p 220k 10 0.01µ 0.01µ 560 23 22 21 12 220p 0.1µ 24 0.1µ 680 10 0.1µ 20 19 18 17 16 15 14 13 N.C. R R PRE ch1 ch2 PRE ch2 ch1 P SW AGC TC PB / REC EP VCA REC 1 2 3 4 5 6 7 8 9 P/R 10 11 0.01µ 0.01µ 7pin SHORT 1.8k 390 12 0.22µ 68k 100µ 0.047µ 0.1µ 100µ 20k PR / REC CTRL REC MIX IN 8 OVER REC CTRL Fig. 1 REC MUTE CTRL PRE OUT EP / SP CTRL HSWP IN 5V 0.01µ Video ICs BA7746S / BA7746FS mode tables •(1)Control REC / PB control Switch between REC and PB using pin 12. Control pin REC / PB Function Mode REC AMP PRE AMP REC + B SW HEAD SW (P) H REC ON OFF ON OFF L PB OFF ON OFF ON (2) OVER REC control Control for OVER REC (current emphasis) is done using pin 9. When in OVER REC mode, the gain setting is recording amplifier AGC level + 1.9dB. Control pin OVER REC Mode Function REC AGC Level H OVER REC 60.0mAP-P L — 48.2mAP-P (3) REC MUTE control Control for REC MUTE when recording is done using pin 8. Control pin REC MUTE Mode Function REC AMP H REC MUTE OFF L — ON (4) EP / SP control EP / SP control during playback is done using pin 4. When EP is selected, the gain of the playback amplifier is increased by 5dB over its normal setting. Control pin EP / SP Mode Function PRE AMP gain H EP Typ. + 5dB L SP Typ. 9 Video ICs BA7746S / BA7746FS •Application example CURRENT SENSE AUDIO HEAD 100p 100p 560 560 220k 680 560 560 0.01µ 0.1µ 12 0.01µ 220p 0.1µ 24 23 22 21 0.1µ 20 19 18 17 16 15 14 13 N. C. R R PRE ch1 ch2 PRE ch2 ch1 P SW AGC TC EP PB / REC VCA REC P/R 1 2 3 4 5 6 7 8 9 10 11 0.01µ 0.22µ 0.01µ 7pin SHORT 1.8k 12 390 68k 100µ 0.047µ 0.1µ 0.01µ 100µ PB / REC CTRL REC MIX IN 10 OVER REC CTRL Fig. 2 REC MUTE CTRL PRE OUT EP / SP CTRL HSWP IN 5V Video ICs BA7746S / BA7746FS notes •(1)Operation preamplifier The preamplifier in this IC is a high-gain amplifier for FM audio. This amplifier has been carefully designed for stability. However, the design of the PCB greatly effects the stability of the preamplifier. A list of general precautions are given below. Take note when designing the PCB. Bad example Input RL 1)The oscillation margin is reduced when the input and output patterns are physically close. The input and output wiring should not come out of the same side of tha IC. Good example Output PRE GND IC MAIN GND Output GND 3)A large GND pattern under the IC has a shielding effect, and reduced the chance of picking up external noise. Input IC Output 4)When the preamplifier is connected to a capacitive load such as shilded wire, or when the output current is large, the output may oscillate. In this case, connect a resistor to the preamplifier output (approx. 390Ω). Bad example IC Input BA7746S / FS BH780XK series 270mVP-P REC Output 2)The GND pattern should be connected at one point to the main IC GND (pin 16). In addition, the preamplifier input-side GND and output-side GND should be as close as possible to the main IC GND. MOD REC LPF MOD FM BPF DE MOD PRE 660mVP-P 390 HEAD AMP Good example REC LPF Hi-Fi AUDIO Connection example for BA7746S / BA7746FS and BH780XK series. Input Output RL PRE GND IC MAIN GND Output GND 11 Video ICs BA7746S / BA7746FS (2) REC amplifier The REC amplifier in this IC is for FM audio. Take note of the following points in order to maintain its commonmode distortion characteristics. 1)Connect the REC AGC FILTER (pin 13) and CURRENT SENSE (pin 14) to the main GND of the IC (pin 16) using leads that are as short as possible. 2)REC NF (pin 11) should be as close to the main IC GND as possible. 3)If you connect a resistor to pin 23 or between pins 24 and 15 to monitor the recording current, the resulting voltage drop may cause the IC to function incorrectly. Use the current sense pin (pin 14) to monitor the recording current. •External dimensions (Units: mm) BA7746S BA7746FS 10.0 ± 0.2 1.778 0.5 ± 0.1 SDIP24 12 7.8 ± 0.3 7.62 0.3 ± 0.1 13 1 12 0.8 0.36 ± 0.1 0.15 ± 0.1 12 24 5.4 ± 0.2 1 1.8 ± 0.1 13 0.11 24 6.5 ± 0.3 0.51Min. 3.4 ± 0.2 3.95 ± 0.3 22.9 ± 0.3 0.3Min. 0.15 0° ~ 15° SSOP-A24