Rohm BA7795 Vcr standard audio signal processor Datasheet

Video ICs
VCR standard audio signal processor
BA7795LS / BA7795FS
The BA7795LS and BA7795FS are standard audio signal processor ICs. They contain a playback preamplifier, line
amplifier, recoeding amplifier, ALC circuit, EQ switch circuit and high-voltage head switch, and provide all of the functions
required for normal-audio signal processing on a single IC with a minimum number of external components required.
Applications
•Video
cassette recorders and tape decks
•1)Features
Available in compact SZIP and SSOP-A24-pin pack2)
3)
4)
5)
Input conversion noise figure – 122dBV
(Typ. Rg = 680, DIN AUDIO).
6) ALC level can be varied.
7) ALC loop external mute eliminates audible noise at
power on, and ALC attack noise.
8) Signal processing circuit can be constructed with the
addition of just a few external components.
ages.
High-with standing-voltage head switch (AC with
standing voltage: Min. 80VP-P (f = 70kHz) ).
Simple, three-mode EQ switch built-in (BA7795LS).
Built-in LINE / TUNER selector switch.
High-performance low-noise playback amplifier.
REC HSW
3
RIPPLE FILTER
5
VCC
7
EQ CTRL
9
PB / TU / EE CTRL
11
ALC LEVEL
13
BIAS
15
EP
LP +
1
REC OUT
21
REC EQ
23
– 8dB
LINE
– 8dB
TUNER
19
GND
6
PB NFB
8
PB EQ
10
PB OUT
12
PB LINE IN
14
ALC FILTER
16
LINE IN
18
TUNER IN
20
GND
22
LINE OUT
24
REC / EE CTRL
REC
– 20dB
MUTE
EP
BF
REC NFB
4
SP
BIAS
PB
17
PB IN
ALC
+ 20dB
LINE
MUTE CTRL
2
PB
REC
HEAD EQ
REC
•Block diagram
BA7795LS
∗
The BA7795FS has a different pin
layout to the BA7795LS.
1
Video ICs
BA7795LS / BA7795FS
•Absolute maximum ratings (Ta = 25°C)
Parameter
Symbol
VCC
Applied voltage
Power
dissipation
BA7795LS
Unit
13
V
400∗1
Pd
BA7795FS
Limits
800∗2
mW
Operating temperature
Topr
– 10 ~ + 65
°C
Storage temperature
Tstg
– 55 ~ + 125
°C
∗1 Reduced by 4.0mW for each increase in Ta of 1°C over 25°C.
∗2 Reduced by 8.0mW for each increase in Ta of 1°C over 25°C.
•Recommended operating conditions (Ta = 25°C)
Parameter
Symbol
Limits
Unit
VCC
7.5 ~ 12.5
V
Power supply voltage
•Pin descriptions
BA7795LS Pin No.
BA7795FS Pin No.
Pin name
1
7
HEAD EQ
2
8
PB IN
Playback amplifier input / playback head switch
3
9
REC HSW
High-withstanding voltage recording head switch
4
10
GND
5
11
RIPPLE FILTER
6
12
PB NFB
7
13
VCC
8
14
PB EQ
9
15
EQ CTRL
10
16
PB OUT
11
17
PB / TU / EE CTRL
12
18
PB LINE IN
Playback line amplifier
13
19
ALC LEVEL
ALC level setting
14
20
ALC FILTER
ALC filter time constant
15
21
BIAS
16
22
LINE IN
17
23
MUTE CTRL
18
24
TUNER IN
Tuner input (REC / EE control)
19
1
REC NFB
Recording amplifier feedback
20
2
GND
21
3
REC OUT
22
4
BF OUT
Line amplifier output
23
5
REC EQ
Recording EQ switch (recording EQ switch 2)
24
6
REC / EE CTRL
2
Function
Head resonance capacitor switch
GND (playback amplifier)
Ripple filter
Playback amplifier feedback
Power supply
Playback EQ switch
EQ control
Playback amplifier output
PB / TU / EE control (PB / EE control)
Bias
Line input
MUTE control
GND
Recording amplifier output
REC / EE control (recording EQ switch 1)
Video ICs
BA7795LS / BA7795FS
•Electrical characteristics (unless otherwise noted, Ta = 25°C, V
CC
Parameter
= 9V, and f = 1kHz)
Symbol
Min.
Typ.
Max.
Unit
Conditions
Quiescent current EE
IqEE
6.3
8.3
10.8
mA
When no signal
Quiescent current PB
IqPB
6.3
8.3
10.8
mA
When no signal
Quiescent current REC
IqREC
4.9
6.4
8.4
mA
When no signal
Power supply gain (PB input)
GVCP
27.0
28.0
29.0
dB
VO = – 8dBV
Power supply gain (LINE1, LINE2, TU inputs)
GVCL
19.0
20.0
21.0
dB
VO = – 8dBV
Distortion
THDL
—
0.1
0.3
%
VO = – 8dBV, RL = 4.7kΩ∗1
Maximum output level
VOmL
5.0
7.2
—
dBV
THD = 1%, RL = 4.7kΩ∗1
Output residual noise
VNOL
—
– 81.5
– 75
dBV
Rg = 4.7kΩ, DIN AUDIO
ALC level
VOA
– 7.0
– 6.0
– 5.0
dBV
VIN = – 23dBV
R1 / R2 = 8.2 / 39kΩ
THDA
—
0.18
0.5
%
VIN = – 23dBV, RL = 4.7kΩ∗1
MT
—
– 82.5
– 72
dB
Vo = 0dBV, DIN AUDIO
Voltage gain
GVCR
19.0
20.0
21.0
dB
LINE, TUNER input→REC OUT
Distortion
THDR
—
0.03
0.3
%
VO = – 8dBV
Maximum output level
VOmR
5.5
7.4
—
dBV
Open loop gain
GVOR
65
77
—
dB
Open loop gain
GVOP
62
Input conversion noise
VNINP
—
– 122.5
– 114
Total gain
GVCP-L
56
57.5
59
dB
PB head switch impedance
RPH
—
11
20
Ω
REC head switch impedance
RRH
—
11
20
Ω
BVRHAC
80
100
—
VP-P
〈Line amplifier〉
ALC distortion
Mute attenuation ratio
〈Recording amplifier〉
VO = – 8dBV, RL = 4.7kΩ∗1
THD = 1%, RL = 4.7kΩ∗1
〈Playback preamplifier〉
68
—
dB
dBV
Rg = 680Ω, DIN AUDIO
PB IN →BF OUT
〈Head switch〉
REC head switch AC withstanding voltage
f = 70kHz
∗1 Measured at BW = 400Hz to 30kHz.
3
Video ICs
BA7795LS / BA7795FS
•Input / output circuits
10kΩ
EQ
CTRL
56kΩ
PB / TU / EE
CTRL
REC / EE
CTRL
56kΩ
MUTE
CTRL
56kΩ
REC
Fig. 1
4
PB
HSW
Video ICs
BA7795LS / BA7795FS
•Measurement circuit
680
3.3µ
+
EP
LP +
1
REC
BA7795LS
PB IN
68k
1k
2
3
5
+
22µ
330
22µ
4
330k
12k
PB
7
0.01µ
6
+
33µ
+
VCC
ON: GVOPB
REC
AC BIAS IN
PB / TU / EE
CTRL
11
SP
9
8.2k
8
EQ CTRL
10
4.7k
R1
13
BIAS
17
– 8dB
TUNER
1.5k
18
4.7k
4.7k
LINE IN
TUNER IN
20
21
4.7k
REC
22
– 20dB
RL
LINE OUT
10µ
MUTE
23
EP
4.7k
+
BF
10µ
+
REC OUT
15k
100µ
+
19
0.1µ
LINE
ON: ALC OFF
16
0.1µ
– 8dB
LINE
ALC
+ 28dB
ON: GVEREC
2.2M
14
15
MUTE CTRL
47µ
+
PB
12
0.1µ
4.7k
R2
24
REC / EE CTRL
Units: R [Ω]
C [F]
∗
The BA7795FS has a different pin layout to the BA7795LS.
Fig. 2
5
Video ICs
BA7795LS / BA7795FS
operation
•(1)Circuit
EE oparation
(2) Recoeding
In recording mode, the recording amplifier directly connected to the line amplifier operates.
The PB HEAD switch in the playback equalizer amplifier block switches on, and the signal is not input to the
playback equalizer amplifier.
The line amplifier output is attenuated by 20dB before it
is input to the recording amplifier, so if the feedback
components are chosen to given a gain of 20dB, the
same REC OUT output level as the line amplifier can
be obtained.
It is also possible to switch the REC equalizer characteristic to suit the tape speed by switchig the control
signal to EQ CTRL. The recording amplifier gain and
equalizer characteristics are set externally.
The input switch is used to select the audio signal input
source (LINE or TUER). This signal is amplified by the
line amplifier (voltage gain: 20dB at 1kHz).
The ALC circuit controls the line amplifier output level.
The ALC level is set externally.
If mute mode is set in this state, the switch that connects the output buffer will go off, but the ALC loop will
not be cut.
EP
LP +
3.3µ
+
1
REC
Signal flow for EE and recording operation
2
3
33µ
REC
330
5
6
7
PB
+
+
VCC
22µ
4
+
22µ
0.01µ
330k
8
EQ CTRL
12k
9
8.2k
4.7k
4.7k
10
PB / TU / EE
CTRL
11
0.1µ
12
PB
+
39k
13
8.2k
BIAS
14
2.2M
ALC
– 8dB
15
LINE
17
– 8dB
1.5k
19
15k
TUNER IN
22
MUTE
– 20dB
RL
LINE OUT
10µ
REC / EE
CTRL
24
EP
Units: R [Ω ]
C [F]
BA7795LS
∗ The BA7795FS has a different pin layout to the BA7795LS.
Fig. 3 Signal flow for EE / recording
6
18
REC
BF
+
REC + B
LINE IN
20
21
23
BIAS
OSC
16
+ 28dB
+
MUTE
CTRL
47µ
Video ICs
BA7795LS / BA7795FS
(3) Playback operation
The signal applied to PB IN is amplified by playback
equalizer amplifier. At this time, the REC HEAD switch
is switched on by a control signal to REC / EE, and the
potential on one side of the head is fixed at GND . The
playback equalizer amplifier gain and equalizer characteristics are set externally. The playback level is set by
the resistor divider between PB OUT and the playback
line input, The signal to the playback line input passes
though the input switch, is amplified by 20dB in the line
amplifier, and is output to the output buffer (the voltage
gain is different to that for the LINE input and TUNER
input).
It is possible to switch between the input block head
equalizer resonance point and playback equalizer characteristic using the EQ CTRL control signal.
The line output can be stopped by setting muting mode
on using the MUTE CTRL signal. The ALC circuit and
recording amplifier are stopped in playback mode.
REC
Signal flow for playback operation
1
3.3µ
EP
LP +
REC
+
2
4
3
22µ
+
33µ
22µ
5
+
VCC
330k
+
6
PB
7
0.01µ
330k
EQ CTRL
9
PB / TU / EE
CTRL
11
SP
8
12k
8.2k
10
4.7k
0.1µ
12
PB
39k
+
13
8.2k
2.2M
LINE
17
– 8dB
ALC
+ 28dB
MUTE
CTRL
LINE IN
16
– 8dB
0.1µ
1.5k
19
15k
+
47µ
14
BIAS
15
4.7k
TUNER IN
18
0.1µ
20
4.7k
REC
21
– 20dB
22
MUTE
23
EP
BF
10µ
+
LINE OUT
10µ
REC / EE CTRL
24
BIAS
OSC
REC + B
BA7795LS
Units: R [Ω]
C [F]
∗ The BA7795FS has a different pin layout to the BA7795LS.
Fig. 4 Signal flow for playback
7
Video ICs
BA7795LS / BA7795FS
mode table
•(1)Control
REC / EE CTRL, PB / TU / EE CTRL
Control pins
Function
Mode
REC / EE
PB / TU / EE
L
L
L
M
TUNER
L
H
PB
LINE
Mode
PB HSW
REC HSW
LINE SW
REC AMP
OFF
ON
LINE
OFF
OFF
ON
TUNER
OFF
OFF
ON
PB
OFF
H
L
LINE REC
ON
OFF
LINE
ON
H
M
TUNER REC
ON
OFF
TUNER
ON
H
H
inhibit
—
—
—
—
If REC / EE CTRL is set to "M", the REC pause state is possible (REC head switch: open, REC amplifier: off).
(2) MUTE CTRL
Control pins
MUTE
Function
Mode
LINE SW
H
MUTE
OPEN
L
MUTE
CLOSE
(3) EQ CTRL
Control pins
Mode
Function
EQ
2 MODE
3 MODE
HEAD EQ SW
PB EQ SW
L
SP
SP
OFF
CLOSE
OFF
M
—
LP
ON
OPEN
OFF
H
EP
EP
ON
OPEN
ON
The L, M and H thresholds are: L to M: 1.7V, L to H: 2.5V, and M to H: 3.3V.
8
REC EQ SW
Video ICs
BA7795LS / BA7795FS
REC
3.3µ
LP
2
REC
+
+
1
EP
•Application example (BA7795LS)
4
3
22µ
+
33µ
330
5
22µ
+
+
VCC
7
EQ CTRL
9
PB
6
0.01µ
330k
SP
8
12k
8.2k
4.7k
4.7k
10
PB / TU / EE
CTRL
11
0.1µ
12
PB
R1
+
13
R2
14
BIAS
2.2M
ALC
+ 28dB
LINE
– 8dB
TUNER
17
1.5k
19
15k
0.1µ
16
LINE IN
0.1µ
18
TUNER IN
20
RL
REC
– 20dB
22
MUTE
23
EP
BF
+
21
+
MUTE CTRL
– 8dB
LINE
15
47µ
LINE OUT
10µ
REC / EE
CTRL
24
BIAS
OSC
Units: R [Ω]
C [F]
REC + B
∗ The BA7795FS has a different pin layout to the BA7795LS.
Fig. 5
9
Video ICs
BA7795LS / BA7795FS
notes
•(1)Operation
ALC level
Set the ALC level in the range – 8dBV to 0dBV by
selecting the values of resistors R1 and R2 connected
between BIAS, ALC LEVEL and GND.
The formula for approximating the value of this resistor
is as follows:
(2) Mute signal
Apply the mute signal shown below at power on and
off. If the muting time is short, a pop sound will be audible, particularly when the power is switched on.
VCC
1
VOA =
2
1
=
2
R1
VCC – 0.7
•
•
R1 + R2
2
R1
• VBIAS
•
R1 + R2
(H)
(H)
2sec or more
MUTE CTRL
LINE OUT
Fig. 7
If the ALC level setting is too low, level variation will
increase compared to that of the standerd level (VOA =
– 6dBV), and conversely, if the level is too high, the
level variation will decrease, but distortion will
increase.There is almost no temperature characteristic,
but the ALC level does vary with supply voltage (VCC)
as shown in the formula above. Use care when setting
it.
Also, be certain to apply the mute signal when switching between PB / LINE / TU. In the case of LINE / TU
switching, it is possible to suppress switching noise by
applying a time constant to the signal, in which case it
is not necessary to apply the mute signal.
(3) Recording control
Do not switch the PB and REC modes on togther. This
will cause faulty operation.
VBIAS =
VCC – 0.7
2
R1
VBIAS
R1 + R2
ALC LEVEL
Fig. 6
10
BIAS
(4) Line output
The line output can drive a load resistance of up to
2kΩ. Depending on the type of load, it can cause local
oscillation (eg. large capacitive loads that draw large
current), so caution is required. In particular, when
there is a possibility that the line output will be connected to a shielded cable, or line cable, connect a resistor
of about 1kΩ in series with the output so that the
capacitive load is not directly coupled to the IC output
terminal.
Video ICs
BA7795LS / BA7795FS
•Electrical characteristic curves
10
40
20
OUTPUT LEVEL: VOA (dBV)
20
10
0
100
1k
10k
100k
0
13
R1 = 18kΩ
R1 5.6kΩ
R1 = 39kΩ
– 10
– 20
– 30
– 40
1M
Fig. 8 Gain vs. frequency (PB amplifier)
– 30
– 10
– 20
0
PB
2
330
22µ
∗ BA7795LS
EP (SW: OFF)
40
SP (SW: ON)
20
100
1k
10k
100k
1M
10µ
+
– 20
RL
LINE
200
500
1k
2k
5k
10k
Fig. 9 Line amplifier ALC input / output
characteristics
Fig. 10 Line amplifier load drive
characteristics
– 70
– 20
– 30
LINE
VCC = 9V
ALC; OFF
DIN AUDIO
– 40
– 50
– 60
– 70
TU→LINE
PB→LINE
– 80
MUTE
– 90
– 100
0
– 10
OUTPUT IMPEDANCE RL (Ω)
– 10
0.01µ
+
60
VCC = 9V
(ALC; OFF)
f = 1kHz
THD = 1%
(0.4 ~ 30kHz)
0
SW
8 10
6
8.2k
330k 12k
OUTPUT LEVEL: VO (dBV)
GVO
80
0
100
10
10
100
10
INPUT LEVEL: VIN (dBV)
FREQUENCY: f (Hz)
GAIN: GVOP – GVC (dB)
R1 = 12kΩ
15
10M
FREQUENCY: f (Hz)
Fig. 11 Playback amplifier frequency
characteristics
– 110
10
100
1k
10k
100k
FREQUENCY: f (Hz)
Fig. 12 Line amplifier crosstalk
OUTPUT NOISE LEVEL: VON (dBV)
GAIN: GVCLT (dB)
30
MAXIMUM OUTPUT LEVEL: VOmL (dBV)
VCC = 9V
f = 1kHz
VCC = 9V
ALC; OFF
– 80
– 90
– 100
DIN AUDIO
VCC = 9V
CIN = 4.7µF
100
200
500
1k
2k
5k
10k
INPUT IMPEDANCE: Rg (Ω)
Fig. 13 Playback amplifier output
noise characteristics
11
Video ICs
BA7795LS / BA7795FS
•External dimensions (Units: mm)
BA7795LS
BA7795FS
2.8 ± 0.2
0.5 ± 0.1
0.1
0.3 +
– 0.05
2.54 ± 0.25
1
23
24
13
1
12
5.4 ± 0.2
7.8 ± 0.3
1.8 ± 0.1
0.889
0.11
2.0Min.
5.8 ± 0.2
9.9 ± 0.5
10.0 ± 0.2
0.8
0.36 ± 0.1
0.15 ± 0.1
21.8 ± 0.2
0.3Min.
0.15
2
24
SZIP24
12
SSOP-A24
Similar pages