ROHM BA7745FS Datasheet

1

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.

2

Video ICs BA7745FS

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Block diagram

17181920212223242526272829303132

16151413121110987654321

REC / PB CTRL

REC AGC FILTER

REC CURRENT SENSE

REC OUT

MAIN GND

PRE AC – FB CH1

PRE AC – FB CH2

PRE IN CH1

PRE GND

PRE IN CH2

REC + B CH2

V

CC REC + B

N.C.

FE V

CC

FE OUT

REC + B CH1

REC NF

REC MIX IN

OVER REC CTRL

REC MUTE CTRL

V

CC

VCA CTRL

N.C.

PRE OUT

EP / SP CTRL

HSWPIN

FE LEVEL

FE3

FE2

FE1

FE GND

FE CTRL

AGC

P / R

P

PB / REC

PREPRE

SW

EP

CH2 CH1

CH2CH1

RR

BF

N.C.

FE OSC

FE

CTRL

N.C.

VCA

REC

•

Absolute maximum ratings (Ta = 25°C)

Parameter

Symbol Limits Unit

V

CC

7.0
V

12.5

Pd 1000

∗

mW
Topr – 10 ~ + 70 °C
Tstg – 55 ~ + 125 °C

PB / REC system

FE system

Power supply voltage

Power dissipation
Operating temperature
Storage temperature

∗

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.

3

Video ICs BA7745FS

•

Recommended operating conditions (Ta = 25°C)

Parameter Symbol Min. Typ. Max. Unit

4.5 5.0 5.5 V

10.5 11.0 11.5 V

V

CCS

Recommended
operating voltage

PB / REC system

FE system

•

Electrical characteristics

Recording system (unless otherwise noted, Ta = 25°C, V

CC = 5V, and f = 1.7MHz)

Parameter Symbol Min. Typ. Max. Unit Conditions

17pin: H

Iq

(REC)

—6690mA

I

OAR

44.7 48.2 51.7

15pin 93.0dBµIN, 19pin OUT

∆I

OAR

10 13 — dB

∆AGC < 0.8dB, 19pin OUT

CMD04— – 50 – 43 dB

15pin MIXIN (∗), 19pin OUT (0.4MHz – 1.3MHz)

CMD09— – 55 – 40 dB

15pin MIXIN (∗), 19pin OUT (0.9MHz – 1.3MHz)

2HD26— – 47 – 40 dB

15pin MIXIN (∗), 19pin OUT (2.6MHz – 1.3MHz)

CMD30— – 42 – 35 dB

15pin MIXIN (∗), 19pin OUT (3.0MHz – 1.3MHz)

2HD34— – 45 – 40 dB

15pin MIXIN (∗), 19pin OUT (3.4MHz – 1.7MHz)

V

14L

0.0 — 2.2 V

3.5 — V

I

OR.OV

+ 1.4 + 1.9 + 2.4 dB

V

13L

0.0 — 2.2 V

V

13H

3.5 — V

I

OR.MU

— – 45 – 40 dB

V

CC

V

CC

mA

P-P

V

14H

∗

f = 1.3MHz (89.0dBµ) + 1.7MHz (97.0dBµ) (MIX)

15pin 93.0dBµIN, 14pin: “H”

15pin 93.0dBµIN, 13pin: “H”

When 14pin DC, NORMAL REC
When 14pin DC, OVER REC

When 13pin DC, MUTE OFF
When 13pin DC, MUTE ON

No signal, pin 12 + pin 29, inflow current

〈

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