Page 1
1
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
•
Features
1) Available in compact SZIP and SSOP-A24-pin packages.
2) High-with standing-voltage head switch (AC with
standing voltage: Min. 80V
P-P (f = 70kHz) ).
3) Simple, three-mode EQ switch built-in (BA7795LS).
4) Built-in LINE / TUNER selector switch.
5) High-performance low-noise playback amplifier.
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.
•
Block diagram
1
3
5
7
9
11
13
15
17
19
21
23
24
22
20
18
16
14
12
10
8
6
4
2 PB IN
GND
PB NFB
PB EQ
PB OUT
PB LINE IN
ALC FILTER
LINE IN
TUNER IN
GND
LINE OUT
REC / EE CTRL
HEAD EQ
REC HSW
RIPPLE FILTER
V
CC
EQ CTRL
PB / TU / EE CTRL
BIAS
MUTE CTRL
REC NFB
ALC LEVEL
REC OUT
REC EQ
ALC
– 20dB
PB
MUTE
BF
REC
– 8dB
TUNER
– 8dB
LINE
LINE
+ 20dB
BIAS
SP
PB
REC
EP
LP +
REC
EP
BA7795LS
∗
The BA7795FS has a different pin
layout to the BA7795LS.
Page 2
2
Video ICs BA7795LS / BA7795FS
•
Pin descriptions
BA7795LS Pin No. BA7795FS Pin No. Pin name Function
17
HEAD EQ
28
PB IN
39
REC HSW
410
GND
511
RIPPLE FILTER
612
PB NFB
713
V
CC
814
PB EQ
915
EQ CTRL
10 16
PB OUT
11 17
PB / TU / EE CTRL
12 18
PB LINE IN
13 19
ALC LEVEL
14 20
ALC FILTER
15 21
BIAS
16 22
LINE IN
17 23
MUTE CTRL
18 24
TUNER IN
19 1
REC NFB
20 2
GND
21 3
REC OUT
22 4
BF OUT
23 5
REC EQ
24 6
REC / EE CTRL
Head resonance capacitor switch
Playback amplifier input / playback head switch
High-withstanding voltage recording head 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)
Playback line amplifier
ALC level setting
ALC filter time constant
Bias
Line input
MUTE control
Tuner input (REC / EE control)
Recording amplifier feedback
GND
Recording amplifier output
Line amplifier output
Recording EQ switch (recording EQ switch 2)
REC / EE control (recording EQ switch 1)
•
Absolute maximum ratings (Ta = 25°C)
•
Recommended operating conditions (Ta = 25°C)
Parameter Symbol Limits Unit
V
CC
13 V
BA7795LS
Pd mW
BA7795FS
Topr °C
Tstg °C
400
∗
1
800
∗
2
– 10 ~ + 65
– 55 ~ + 125
∗
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.
Applied voltage
Power
dissipation
Operating temperature
Storage temperature
Parameter Symbol Limits Unit
7.5 ~ 12.5 VV
CC
Power supply voltage
Page 3
3
Video ICs BA7795LS / BA7795FS
•
Electrical characteristics (unless otherwise noted, Ta = 25°C, VCC = 9V, and f = 1kHz)
Parameter Symbol Min. Typ. Max. Unit Conditions
I
qEE 6.3 8.3 10.8 mA
I
qPB 6.3 8.3 10.8 mA
I
qREC 4.9 6.4 8.4 mA
G
VCP 27.0 28.0 29.0 dB V
O
= – 8dBV
G
VCL 19.0 20.0 21.0 dB V
O
= – 8dBV
THD
L — 0.1 0.3 % V
O
= – 8dBV, RL = 4.7kΩ
∗
1
V
OmL 5.0 7.2 — dBV THD = 1%, RL = 4.7kΩ
∗
1
V
NOL — – 81.5 – 75 dBV Rg = 4.7kΩ, DIN AUDIO
V
OA – 7.0 – 6.0 – 5.0 dBV
R
1 / R2 = 8.2 / 39kΩ
V
IN = – 23dBV
THD
A — 0.18 0.5 % VIN = – 23dBV, RL = 4.7kΩ
∗
1
MT — – 82.5 – 72 dB Vo = 0dBV, DIN AUDIO
G
VCR 19.0 20.0 21.0 dB
THD
R — 0.03 0.3 % VO = – 8dBV
V
OmR 5.5 7.4 — dBV VO = – 8dBV, RL = 4.7kΩ
∗
1
G
VOR 65 77 — dB THD = 1%, RL = 4.7kΩ
∗
1
G
VOP 62 68 — dB
V
NINP — – 122.5 – 114 dBV Rg = 680Ω, DIN AUDIO
G
VCP-L 56 57.5 59 dB PB IN →BF OUT
R
PH — 11 20 Ω
R
RH — 11 20 Ω
BV
RHAC 80 100 — V
P-P
f = 70kHz
LINE, TUNER input→REC OUT
∗
1 Measured at BW = 400Hz to 30kHz.
When no signal
When no signal
When no signal
Quiescent current EE
Quiescent current PB
Quiescent current REC
〈Line amplifier〉
Power supply gain (PB input)
Power supply gain (LINE1, LINE2, TU inputs)
Distortion
Maximum output level
Output residual noise
ALC level
ALC distortion
Mute attenuation ratio
〈Recording amplifier〉
Voltage gain
Distortion
Maximum output level
Open loop gain
〈Playback preamplifier〉
Open loop gain
Input conversion noise
Total gain
〈Head switch〉
PB head switch impedance
REC head switch impedance
REC head switch AC withstanding voltage
Page 4
4
Video ICs BA7795LS / BA7795FS
•
Input / output circuits
10kΩ
EQ
CTRL
56kΩ
PB / TU / EE
CTRL
MUTE
CTRL
56kΩ
REC / EE
CTRL
56kΩ
REC PB
HSW
Fig. 1
Page 5
5
Video ICs BA7795LS / BA7795FS
Units: R [Ω]
1
3
5
7
9
11
13
15
17
19
21
23
24
22
20
18
16
14
12
10
8
6
4
2
– 20dB
PB
MUTE
BF
REC
– 8dB
TUNER
– 8dB
LINE
LINE
+ 28dB
BIAS
SP
PB
REC
EP
LP +
REC
AC BIAS IN
1k
22µ
33µ
VCC
EQ CTRL
PB / TU / EE
CTRL
R2
R1
MUTE CTRL
15k
100µ
10µ
ON: GVEREC
REC OUT
4.7k
68k
680
3.3µ
330
ON: GVOPB
22µ
330k
12k
8.2k
0.01µ
4.7k
4.7k
47µ
0.1µ
2.2M
ON: ALC OFF
LINE IN
4.7k
4.7k
4.7k
0.1µ0.1µ
10µ
RL
TUNER IN
LINE OUT
REC / EE CTRL
EP
PB IN
1.5k
ALC
Fig. 2
∗
The BA7795FS has a different pin layout to the BA7795LS.
C [F]
+
+
+
+
+
+
+
+
•
Measurement circuit
BA7795LS
Page 6
6
Video ICs BA7795LS / BA7795FS
•
Circuit operation
(1) EE oparation
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.
(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.
Signal flow for EE and recording operation
C [F]
Units: R [Ω ]
1
3
5
7
9
11
13
15
17
19
21
23
24
22
20
18
16
14
12
10
8
6
4
2
– 20dB
PB
MUTE
BF
REC
– 8dB
– 8dB
LINE
+ 28dB
BIAS
PB
REC
EP
LP
+
REC
EP
22µ
33µ
V
CC
EQ CTRL
PB / TU / EE
CTRL
39k
8.2k
MUTE
CTRL
1.5k
15k
BIAS
OSC
REC + B
3.3µ
330
22µ
0.01µ
330k
12k
8.2k
4.7k 4.7k
0.1µ
47µ
2.2M
LINE IN
TUNER IN
R
L
LINE OUT
10µ
REC / EE
CTRL
BA7795LS
ALC
∗
The BA7795FS has a different pin layout to the BA7795LS.
Fig. 3 Signal flow for EE / recording
+
+
+
+
+
+
+
Page 7
7
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.
Signal flow for playback operation
1
3
5
7
9
11
13
15
17
19
21
23
2
4
6
8
10
12
14
16
18
20
22
24
+
+
+
+
+
REC + B
22µ
33µ
22µ
10µ
0.1µ
47µ
0.01µ
39k
ALC
LINE
3.3µ
330k
330k
12k
8.2k
4.7k 4.7k
0.1µ
V
CC
EP
REC
BIAS
– 20dB
MUTE
BF
– 8dB
– 8dB
PB
PB
SP
REC
2.2M
4.7k
8.2k
15k
1.5k
10µ
EP
LP
+
REC
+ 28dB
0.1µ
REC / EE CTRL
EQ CTRL
PB / TU / EE
CTRL
MUTE
CTRL
BIAS
OSC
LINE IN
TUNER IN
LINE OUT
BA7795LS
C [F]
Units: R [Ω]
∗
The BA7795FS has a different pin layout to the BA7795LS.
Fig. 4 Signal flow for playback
+
+
Page 8
8
Video ICs BA7795LS / BA7795FS
•
Control mode table
(1) REC / EE CTRL, PB / TU / EE CTRL
L L OFF ON LINE OFF
L M TUNER OFF ON TUNER OFF
L H PB OFF ON PB OFF
H L ON OFF LINE ON
H M ON OFF ON
H H inhibit ————
TUNER
LINE REC
TUNER REC
REC / EE PB / TU / EE PB HSW REC HSW LINE SW REC AMP
Mode
Control pins Function
If REC / EE CTRL is set to "M", the REC pause state is possible (REC head switch: open, REC amplifier: off).
Mode
LINE
(2) MUTE CTRL
MUTE
H MUTE OPEN
L MUTE CLOSE
LINE SW
Function
Mode
Control pins
(3) EQ CTRL
E Q
L SP SP OFF CLOSE OFF
M — LP ON OPEN OFF
H EP EP ON OPEN ON
2 MODE 3 MODE HEAD EQ SW PB EQ SW REC EQ SW
Control pins Mode Function
The L, M and H thresholds are: L to M: 1.7V, L to H: 2.5V, and M to H: 3.3V.
Page 9
9
Video ICs BA7795LS / BA7795FS
•
Application example (BA7795LS)
1
3
5
7
9
11
13
15
17
19
21
23
2
4
6
8
10
12
14
16
18
20
22
24
REC + B
22µ
33µ
22µ
10µ
47µ
0.01µ
ALC
LINE
3.3µ
330k
12k
8.2k
4.7k 4.7k
0.1µ
V
CC
EP
REC
BIAS
– 20dB
MUTE
BF
– 8dB
PB
PB
SP
REC
2.2M
15k
EP
LP
+
REC
+ 28dB
0.1µ
R1
R2
1.5k
LINE
– 8dB
TUNER
RL
330
EQ CTRL
MUTE CTRL
LINE OUT
PB / TU / EE
CTRL
BIAS
OSC
REC / EE
CTRL
0.1µ
LINE IN
TUNER IN
Fig. 5
∗
The BA7795FS has a different pin layout to the BA7795LS.
Units: R [Ω]
C [F]
+
+
+
+
+
+
+
Page 10
10
Video ICs BA7795LS / BA7795FS
•
Operation notes
(1) 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:
If the ALC level setting is too low, level variation will
increase compared to that of the standerd level (V
OA =
– 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 (V
CC)
as shown in the formula above. Use care when setting
it.
(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.
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.
(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.
2sec or more
(H)
V
CC
MUTE CTRL
LINE OUT
(H)
Fig. 7
2
VCC – 0.7
R
1
R1 + R2
• VBIAS
VOA =
=
•
•
1
R
1
R1 + R
2
2
1
2
•
2
VCC – 0.7
R
1
R1 + R
2
V
BIAS
VBIAS = BIAS
ALC LEVEL
Fig. 6
Page 11
11
Video ICs BA7795LS / BA7795FS
•
Electrical characteristic curves
VCC = 9V
ALC; OFF
40
30
20
10
0
100 1k 10k 100k 1M
FREQUENCY: f (Hz)
GAIN: GVCLT (dB)
Fig. 8 Gain vs. frequency (PB amplifier)
– 20
VCC = 9V
f = 1kHz
13 15
R1
5.6kΩ
R1 = 18kΩ
R1 = 12kΩ
R1 = 39kΩ
10
0
– 10
– 20
– 30
– 40 – 30 – 10 0 10
INPUT LEVEL: V
IN (dBV)
OUTPUT LEVEL: VOA (dBV)
Fig. 9 Line amplifier ALC input / output
characteristics
VCC = 9V
(ALC; OFF)
f = 1kHz
THD = 1%
(0.4 ~ 30kHz)
+
10µ
LINE
R
L
100 200 500 1k 2k 5k 10k
– 20
– 10
0
10
20
OUTPUT IMPEDANCE R
L (Ω)
MAXIMUM OUTPUT LEVEL: VOmL (dBV)
Fig. 10 Line amplifier load drive
characteristics
PB
SW
8.2k
330k
330
+
0.01µ
22µ
2
6
8
10
12k
100 1k 10k 100k 1M 10M
0
20
40
60
80
100
FREQUENCY: f (Hz)
GAIN: GVOP – GVC (dB)
GVO
SP (SW: ON)
EP (SW: OFF)
∗
BA7795LS
Fig. 11 Playback amplifier frequency
characteristics
VCC = 9V
ALC; OFF
DIN AUDIO
LINE
TU→
LINE
PB→LINE
10 100 1k 10k 100k
10
0
–
20
–
10
–
30
–
40
–
50
–
60
–
70
–
80
–
90
–
100
–
110
OUTPUT LEVEL: VO (dBV)
FREQUENCY: f (Hz)
MUTE
Fig. 12 Line amplifier crosstalk
DIN AUDIO
V
CC = 9V
C
IN = 4.7µF
100 200 500 1k 2k 5k 10k
–
70
–
80
–
90
–
100
INPUT IMPEDANCE: Rg (Ω)
OUTPUT NOISE LEVEL: VON (dBV)
Fig. 13 Playback amplifier output
noise characteristics
Page 12
12
Video ICs BA7795LS / BA7795FS
SZIP24
BA7795LS BA7795FS
SSOP-A24
5.8
±
0.2
9.9 ± 0.5
0.889
1
2
23
24
0.5 ± 0.1
+
0.1
–
0.05
2.54 ± 0.25
0.3
2.0Min.
21.8 ± 0.2
2.8 ± 0.2
0.15
0.3Min.
7.8 ± 0.3
5.4 ± 0.2
1.8 ± 0.1
0.11
1
24
0.36 ± 0.1
10.0 ± 0.2
12
13
0.8
0.15 ± 0.1
•
External dimensions (Units: mm)
Loading...