Rohm BA7746FS Vcr hi-fi audio signal rec / pb amplifier Datasheet

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