BA7746FS

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 •Features playback amplifier has a total gain of 1) The low-noise 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 VCC Pd Topr Tstg Limits 7.0 1050∗1 800∗2 – 10 ~ + 70 – 55 ~ + 125 Unit V mW mW °C °C Operating temperature Storage temperature ∗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 VCCS Min. 4.5 Typ. 5.0 Max. 5.5 Unit V •Block diagram P/R REC AGC FILTER 13 12 REC / PB CTRL REC CURRENT SENSE 14 AGC 11 REC NF REC REC OUT 15 10 REC MIX IN P MAIN GND 16 PB / REC 9 OVER REC CTRL PRE AC – FB ch1 17 ch1 8 REC MUTE CTRL PRE PRE IN ch1 18 7 VCC SW EP PRE GND 19 6 VCA CTRL (PRE MUTE) PRE VCA PRE IN ch2 20 5 PRE OUT PRE AC – FB ch2 ch2 21 4 EP / SP CTRL N.C. N.C. 22 3 ch2 HSWP IN REC + B ch2 23 R ch1 TC 2 REC TC REC + B ch1 24 R 1 VCC REC + B 2 Video ICs BA7746S / BA7746FS •Pin descriptions Pin No. Pin name, function and remarks Voltage Circuit diagram 〈VCC REC + B〉 • Power supply for REC + B. • Connect to VCC (pin 7). 1 VCC — 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 REC: 0.9V PB: 0V REC 20k 3 〈HSWP IN〉 • Pulse input for head switching. • ch1: H, ch2: L — 24k 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 — 40k EP SP 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 REC: 3.6V PB: 1.9V (RL: 1.8kΩ) 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 30k REC: 2.0V PB: 2.0V 580 20k MUTE H 3 Video ICs Pin No. Pin name, function and remarks Voltage BA7746S / BA7746FS Circuit diagram 7 〈VCC〉 • Power supply for anything other than REC + B. VCC — 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. — 30k MUTE REC 9 〈OVER REC CTRL〉 • OVER REC control. • In OVER REC mode, the recording current is set to + 2dB (Typ.). • Do not leave open circuit. — 30k OVER NORMAL 10 〈REC MIX IN〉 • Recording amplifier input. REC: 2.9V PB: 2.9V 10k 10k 11 〈REC NF〉 • Recording amplifier feedback. • Connect the GND of a decoupling capacitor to main GND (pin 16) to improve common-mode distortion. 10.2k REC: 1.4V PB: 0.5V 240 1.04k 12 〈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. — 30k 4 Video ICs Pin No. Pin name, function and remarks Voltage BA7746S / BA7746FS Circuit diagram 13 〈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 2k 2k 14 〈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 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 14 REC: 4.1V PB: 0V 16 〈MAIN GND〉 • Earth for circuits other than the preamplifier. • Reference potential for the IC GND — 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 REC: 0V PB: 0.8V 4k 17 13k 18 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.). REC: 0V PB: 0.7V 5 Video ICs Pin No. Pin name, function and remarks Voltage BA7746S / BA7746FS Circuit diagram 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). GND — 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.). 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 characteristics •Electricalmode (pin 12→ "H") (unless otherwise noted, Ta = 25°C, V Recording Parameter Quiescent current Output current AGC level Output current AGC level Cross modulation distortion 0.4MHz component Cross modulation distortion 0.9MHz component OVER REC holding voltage OVER REC holding voltage Current emphasis OVER REC MUTE holding voltage REC MUTE holding voltage Mute attenuation Symbol Iq (REC) BA7746S / BA7746FS CC = 5.0V, and f = 1.7MHz) Conditions No signal, pin 1 + pin 7, inflow current 10pin 93.0dBµIN, 14pin OUT ∆AGC Min. — 44.2 10 — — 0.0 3.5 1.4 0.0 3.5 — Typ. 66 48.2 13 – 50 – 55 — — 1.9 — — – 50 Max. 90 52.2 — – 40 – 40 2.2 VCC 2.4 2.2 VCC – 40 Unit mA mAP-P dB dB dB V V dB V V dB IOAR ∆IOAR CMD04 CMD09 V9L V9H IOR.OV V8L V8H IOR.MU < 0.8dB, 14pin OUT 10pin MIXIN∗, 14pin OUT (0.4MHz - 1.3MHz) 10pin MIXIN∗, 14pin OUT (0.9MHz - 1.3MHz) 9pin DC, When NORMAL REC 9pin DC, When OVER REC 10pin 93.0dBµIN, 9pin: “H” 8pin DC, When MUTE OFF 8pin DC, When MUTE ON 10pin 93.0dBµIN, 8pin: “H” ∗ 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) Parameter Supply current Voltage gain CH1 Symbol Iq 〈PB〉 GVP1 Min. — 75 Typ. 19 79 Max. 31 83 Unit mA dB Conditions Inflow current to pin 7 when no signal. 18pin, 20.5dBµIN, 5pin OUT, 3pin: “H” 20pin, 20.5dBµIN, 5pin OUT, 3pin: “L” 18pin, 20pin, 20.5dBµ, ∆5pin OUT 18pin 31.0dBµ, 20pin 0 IN, 3pin: “H”→ “L”, ∆5pin OUT 18pin 0, 20pin 31.0dBµIN, 3pin: “L”→ “H”, ∆5pin OUT 18pin 20.5dBµIN, 3pin: “H” f = 2.2MHz / 1.0MHz, ∆5pin OUT 20pin 20.5dBµ IN, 3pin: “L” f = 2.2MHz / 1.0MHz, ∆5pin OUT 6pin 3.2V, ∆5pin OUT 6pin 0.8V, ∆5pin OUT Pin 18 and 20 IN, pin 5 OUT 3rd-harmonic distortion, when-30dB. Input conversion for pin 18: 0.01µ F + 10Ω at GND Pin 3: “H”, pin 5 OUT. Input conversion for pin 20: 0.01µF + 10Ω at GND Pin 3: “L”, pin 5 OUT. Voltage gain CH2 GVP2 ∆GVP CT1→2 CT2→1 75 79 83 dB Voltage gain differential – 2.0 0 2.0 dB CH1 to CH2 crosstalk — – 45 – 35 dB CH2 to CH1 crosstalk — – 45 – 35 dB CH1 frequency characteristic fP1 0 – 2.4 –5 dB CH2 frequency characteristic Gain adjustment headroom Gain adjustment headroom Maximum output voltage fP2 – ∆GVCA + ∆GVCA 0 — 4 2.0 – 2.4 – 50 6 2.6 –5 – 35 — — dB dB dB VP-P µVrms µVrms VOMP CH1 input conversion noise VNP1 — 0.4 1.0 CH2 input conversion noise VNP2 — 0.4 1.0 7 Video ICs BA7746S / BA7746FS •Electrical characteristics"L") (unless otherwise noted, Ta = 25°C, V Playback mode (pin 12→ Parameter Head switching voltage Head switching voltage Output DC offset PB holding voltage REC holding voltage Head switch ON resistance SP holding voltage EP holding voltage Gain emphasis EP Symbol VHS2 VHS1 ∆VODC V12L V12H RSWP V4L V4H GVP.EP Min. 0.0 2.8 – 20 0.0 3.5 — 0.0 3.5 4.0 Typ. — — 0 — — 5 — — 5.0 Max. 2.2 VCC 20 1.0 VCC 10 2.2 VCC 6.0 CC = 5.0V, and f = 1.5MHz) Conditions Pin 3 DC when ch2 operating Pin 3 DC when ch1 operating 18, 20pin 0 IN, 3pin “H”→ “L” ∆5pin OUT Pin 12 DC for PB mode Pin 12 DC for REC mode Pin 15 ON resistance Pin 4 DC for SP mode Pin 4 DC for EP mode 18, 20pin 20.5dBµIN, 4pin: “H”, 5pin OUT Unit V V mV V V Ω V V dB •Measurement circuit 1k PRE IN ch2 100p 12µ 12µ 560 0.1µ 100p 10 0.01µ PRE IN ch1 1k 680 560 220p 0.1µ 17 16 15 14 CURRENT SENSE 220k 12 0.1µ 10 0.01µ 24 23 22 N.C. 21 20 19 18 13 R ch1 R PRE ch2 ch2 PRE ch1 P SW AGC TC EP PB / REC VCA REC P/R 1 7pin SHORT 2 3 4 1.8k 5 6 7 0.01µ 8 9 10 0.01µ 11 12 0.22µ 68k 390 0.047µ 100µ 0.1µ 100µ 20k 5V OVER REC CTRL REC MUTE CTRL HSWP IN REC MIX IN PR / REC CTRL EP / SP CTRL PRE OUT 0.01µ Fig. 1 8 Video ICs BA7746S / BA7746FS •Control/ mode tables (1) REC PB control Switch between REC and PB using pin 12. Control pin REC / PB H L Mode REC PB REC AMP ON OFF Function PRE AMP OFF ON REC + B SW ON OFF HEAD SW (P) 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 H L Mode OVER REC — Function REC AGC Level 60.0mAP-P 48.2mAP-P (3) REC MUTE control Control for REC MUTE when recording is done using pin 8. Control pin REC MUTE H L Mode REC MUTE — Function REC AMP OFF 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 H L Mode EP SP Function PRE AMP gain Typ. + 5dB Typ. 9 Video ICs BA7746S / BA7746FS •Application example CURRENT SENSE AUDIO HEAD 100p 100p 220k 680 560 12 220p 0.1µ 560 560 0.01µ 0.1µ 24 23 22 N. C. R R PRE ch1 ch2 ch2 21 20 19 560 0.01µ 0.1µ 18 17 16 15 14 13 PRE ch1 P SW AGC TC EP PB / REC VCA REC P/R 1 2 3 4 5 6 7 0.01µ 8 9 10 0.01µ 11 12 0.22µ 68k 1.8k 390 0.047µ 0.01µ 7pin SHORT 100µ 0.1µ 100µ 5V EP / SP CTRL PRE OUT REC MUTE CTRL OVER REC CTRL PB / REC CTRL REC MIX IN HSWP IN Fig. 2 10 Video ICs BA7746S / BA7746FS •Operation notes (1) 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. 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 Bad example Input Output RL 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. IC Output Input Bad example 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). IC BA7746S / FS REC 270mVP-P BH780XK series REC LPF REC LPF MOD Input Output MOD 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. Good example Input Output PRE 660mVP-P 390 FM BPF DE MOD HEAD AMP Hi-Fi AUDIO Connection example for BA7746S / BA7746FS and BH780XK series. 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 22.9 ± 0.3 24 13 6.5 ± 0.3 7.8 ± 0.3 5.4 ± 0.2 24 10.0 ± 0.2 13 0.51Min. 3.4 ± 0.2 3.95 ± 0.3 7.62 1.8 ± 0.1 1 0.3 ± 0.1 12 0.11 0.8 0.36 ± 0.1 0.3Min. 0.15 1.778 0.5 ± 0.1 0° ~ 15° SDIP24 SSOP-A24 12 0.15 ± 0.1 1 12