ROHM BA7757BK Datasheet

1

Video ICs

Switchless REC / PB amplifier for
standard audio signal processing

BA7757BK

The BA7757BK contains a playback equalizer amplifier, an REC / PB switch, a line amplifier, an ALC circuit with
built-in detector, a recording amplifier, an analog switch for input switching, and a logic control circuit for independent
switching of REC / EE, PR / EE, line mute and input.
The IC is easy to interface with control systems, and features low noise during mode switching and at power on / off.
The line amplifier and recording amplifire are directly connected internally, allowing construction of a high-perfor­mance audio signal processing circuit for VCRs using a minimum number of external components.

•

Features

1) All necessary switches for audio signal processing
are built-in.

· MIC / LINE input selector switch.

· EP / SP equalizer selector switch.

· Built-in head switch on the playback side of the
head for head switching for REC / PB, and a head­switch driver terminal provided on the recording
side.

· EE / PB and EE / REC selector switches (compati­bility with after-recording mode (AFR) is possible).

· Line muting switch.

2) All control functions are independent, so interfacing
with the control system is simple.

3) Amplifiers required for audio recording and play­back are provided on the IC.

4) Excellent S / N and distortion specifications through
use of high-level ALC VR.

5) The ALC level is set using a external resistor, and
variation due to temperature is extremely low.

6) Built-in ripple filter gives excellent ripple rejection.

7) Low noise generation when power is switched on
and off, and during control system switching.

8) The line output can directly drive earphone.

9) Few external parts required.

10) Available in a QFP32 package, for high-density
mounting.

11) Low power consumption.

2

Video ICs BA7757BK

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Block diagram

81234567

32

25EP SW

PB NF

FILTER

SP SW

V

CC

Vreg

PB OUT

LINE REC IN

LINE PB IN

BIAS 1

(V

CC

/

2)

LINE NFB

N.C.

BIAS 2

ALC FILTER

AGC VR CTRL

ALC LEVEL

MUTE CTRL

1724 23 22 21 20 19 18

GND

PB IN

LINE / MIC INPUT CTRL

INPUT SW OUT

LINE IN

MIC IN

FREQ. COMPENSATION

GND

26

27

28

29

30

31

EP SW

EP / SP CTRL

REC NFB

EE / REC CTRL

REC OUT

EE / PB CTRL

– 24.4dB

39.2dB
HEAD SW CTRL

LINE OUT

16

15

14

13

12

11

REC

LINE

10

9

R

P

BF

BIAS

BIAS

ALC

PB

120kΩ

INPUT SW