Document
Video ICs
VCR Hi-Fi audio signal REC / PB amplifier with flying-erase oscillator
BA7745FS
The BA7745FS has the recording and playback amplifiers required for Hi-Fi VCR signal processing, and also contains a flying-erase oscillator. The recording system uses a constant-current amplifeir 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, a VCA and an EP-gain amplifier. The flying-erase oscillator has low 2nd and 3rd harmonic distortion, and when connected to an external driver large output current can be obtained. A H / L control system eliminates the need for special power supplies for the recording and playback systems. The IC has low power consumption, and comes in a compact 32-pin SSOP-P 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 The low-noise playback amplifier has a total gain of
83dB (Typ.). Designed for VHS-bandoperation with low external parts count. It has two built-in circuits for Hi-Fi VCR operation. 2) The circuit has been designed to suppress headswitching noise. 3) Built-in EP / SP gain switching function that boosts the playback gain by 5dB. 4) Built-in VCA for easy playback output adjustment. 5) High-output recording amplifier for audio FM recording. 6) Constant-current drive provides 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) Built-in high-frequency oscillator for use with flying erase function. 11) Record / playback switching can be done directly via the system controller, and consumes litlle power. 12) Possible to construct a high-performance audio system by pairing this chip with a Hi-Fi-audio signal processing IC.
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Video ICs
BA7745FS
•Block diagram
P/R 17 16 AGC REC 15 14 13 P 12 PB / REC 11 VCA 10 9 N.C. 8 CH2 CH2 7 6 FE CTRL 5 FE OSC BF 4 N.C. 3 2 1 CH1 EP SW PRE CH1 PRE R R REC / PB CTRL REC NF 18 REC AGC FILTER REC MIX IN
19
REC CURRENT SENSE
OVER REC CTRL
20
REC OUT
REC MUTE CTRL
21
MAIN GND
VCC
22
PRE AC – FB CH1
VCA CTRL
23
PRE IN CH1
PRE OUT
24
PRE GND
EP / SP CTRL
25
PRE IN CH2
HSWPIN
26
PRE AC – FB CH2
N.C.
27
REC + B CH2
FE LEVEL
REC + B CH1
28
FE CTRL
VCC REC + B
29
FE3
N.C.
30
FE2
FE VCC
31
FE1
FE OUT
32
FE GND
•Absolute maximum ratings (Ta = 25°C)
Parameter Power supply voltage Power dissipation Operating temperature Storage temperature Symbol VCC Pd Topr Tstg Limits PB / REC system FE system 1000∗ – 10 ~ + 70 – 55 ~ + 125 7.0 12.5 Unit V mW °C °C
∗
When mounted on a 90mm × 50mm × 1.6mm glass epoxy board, reduced by 10mW for each increase in Ta of 1°C over 25°C.
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Video ICs
BA7745FS
•Recommended operating conditions (Ta = 25°C)
Parameter Recommended operating voltage PB / REC system FE system Symbol VCCS Min. Typ. Max. 4.5 5.0 5.5 Unit V V 10.5 11.0 11.5
Electrical characteristics • Recording system (unless otherwise noted, Ta = 25°C, V
Parameter 〈Recording mode〉 Quiescent current Output current AGC level Output current AGC range Cross modulation distortion 0.4MHz component Cross modulation distortion 0.9MHz component 2nd-harmonic distortion 2.6MHz component Cross modulation distortion 3.0MHz component 2nd-harmonic distortion 3.4MHz 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) IOAR ∆IOAR CMD04 CMD09 2HD26 CMD30 2HD34 V14L V14H IOR.OV V13L V13H IOR.MU Min.
CC
= 5V, and f = 1.7MHz)
Max. 90 51.7 — – 43 – 40 – 40 – 35 – 40 2.2 VCC + 2.4 2.2 VCC – 40 Unit mA mAP-P dB dB dB dB dB dB V V dB V V dB Conditions 17pin: H No signal, pin 12 + pin 29, inflow current 15pin 93.0dBµIN, 19pin OUT ∆AGC < 0.8dB, 19pin OUT 15pin MIXIN (∗), 19pin OUT (0.4MHz – 1.3MHz) 15pin MIXIN (∗), 19pin OUT (0.9MHz – 1.3MHz) 15pin MIXIN (∗), 19pin OUT (2.6MHz – 1.3MHz) 15pin MIXIN (∗), 19pin OUT (3.0MHz – 1.3MHz) 15pin MIXIN (∗), 19pin OUT (3.4MHz – 1.7MHz) When 14pin DC, NORMAL REC When 14pin DC, OVER REC 15pin 93.0dBµIN, 14pin: “H” When 13pin DC, MUTE OFF When 13pin DC, MUTE ON 15pin 93.0dBµIN, 13pin: “H”
Typ.
— 66 44.7 48.2 10 13 — – 50 — – 55 — – 47 — – 42 — – 45 0.0 — 3.5 — + 1.4 + 1.9 0.0 — 3.5 — — – 45
∗ f = 1.3MHz (89.0dBµ) + 1.7MHz (97.0dBµ) (MIX)
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Video ICs
Playback system (unless otherwise noted, Ta = 25°C, VCC = 5V, and f = 1.5MHz)
Parameter 〈Playback mode〉 Supply current Voltage gain CH1 Voltage gain CH2 Voltage gain differential CH1 to CH2 crosstalk CH2 to CH1 crosstalk CH1.