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Part: BA7746FS
Category:
Multimedia
-> Video
Description:
Company: ROHM Electronics
Datasheet: Download BA7746FS datasheet File size : 124 kB
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Datasheet text preview:
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. Ap ·CRplications Vs
res ·)FTehaetulow-noise playback amplifier has a total gain of 1 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. C o n s t a n t - c u r r e n t drive povides stable recording characteristics when the load (head impedance) is fluctuating.
2) 3) 4) 5) 6)
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) B u i l t - i n 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 v i a the system controller, and consumes littele power. 12) P o s s i b l e 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 10501 8002 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
V CC
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 20k. · 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. 390). · Avoid capacitive coupling with the playback input
REC: 3.6V PB: 1.9V (RL: 1.8k)
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. 12...48.2mAP-P, 15...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
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