1
Video ICs
High-voltage audio head selection
switch
BA7755A / BA7755AF
The standard audio circuits of video cassette recorders and the recording circuits of tape decks use AC bias record-
ing to record the audio signal onto the tape. This bias voltage is some tens of volts, and a high-capacity bias-side
switch is required to electronically switch the head when in playback or record mode.
The BA7755A and BA7755AF are high-voltage switching ICs designed to switch voltages as high as 65V
DC
or
AC120V
P-P
(f = 70Hz).
Two control systems, one for current control, and one for voltage control are provided, so the ICs can be used in cir-
cuits that employ either method.
By combining the BA7755A or BA7755AF with the BA7751ALS recording / playback amplifier, it is possible to con-
struct a compact recording / playback audio circuit. In addition, the BA7755A and BA7755AF are an excellent choice
for a wide variety of other high-voltage switching applications.
Applications
Video cassette recorders and tape decks
Features
1) High withstanding voltage ( 65V
DC
(Min.),
AC120V
P-P
(Min.), f = 70Hz).
2) Circuits for either current control or voltage control
are provided on the chip.
3) Compact SIP 5pin or SOP 8pin package.
Block diagram
BA7755AF
1
2
3
4
5
SW
GND CTRL2 CTRL1
BA7755A
V
CC
8
7
6
5
1
2
3
4
N.C.
N.C.
N.C.
HEAD
SWITCH
GND CTRL2
CTRL1
V
CC
2
Video ICs
BA7755A / BA7755AF
Absolute maximum ratings (Ta = 25C)
Parameter
Symbol
Limits
Unit
V
CC
15
V
Pd
400
1
mW
Topr
10 ~ + 65
C
Tstg
55 ~ + 125
C
BV
CC2
65
V
Reduced by 4mW for each increase in Ta of 1
C over 25
C.
Power supply voltage
Power dissipation
Operating temperature
Storage temperature
Breakdown voltage of switch (pin 2)
Recommended operating conditions (Ta = 25C)
Parameter
Unit
V
Max.
13
9
Typ.
Min.
4
Symbol
V
CC
Operating voltage
Electrical characteristics (unless otherwise noted, Ta = 25C and V
CC
= 9V)
Parameter
Symbol
Min.
Typ.
Max.
Unit
Conditions
I
CC1
--
0
10
A
Pin4 "L" or "OPEN"
Pin5 "OPEN"
I
CC2
2.4
3.9
5.6
mA
Pin 4 "L" or "OPEN"
Pin 5 control current: 200
A
R
ON
--
8.0
15.0
Pin 4 "L" or "OPEN"
Pin 5 control current: 200
A
I
LOFF
--
0
10
A
Pin 4 "H", or "OPEN", or "L"
Pin 5 "OPEN", pin 2 applied voltage
65V
BV
AC
120
160
--
V
P-P
f = 70kHz
V
OS
--
4.3
15.0
mV
Pin 4 "L" or "OPEN"
Pin 5 control current: 200
A
I
CTRL1 (ON)
50
--
--
A
--
I
CTRL1 (OFF)
--
--
1
A
--
V
TH1
1.70
2.15
2.60
V
--
R
CTRL2
21.0
31.0
42.0
k
--
Supply current
Supply current
Switch-on resistance
Switch leakage current
Switch AC breakdown voltage
Switch offset voltage
CTRL1 SW ON control current
CTRL1 SW OFF control current
CTRL2 threshold voltage
CTRL2 input resistance
3
Video ICs
BA7755A / BA7755AF
Switch control methods
(1) Control with pins 4 and 5
BA7755A
1
2
3
4
5
SW1
SW2
5V
R
V
CC
Fig. 1
Head
SW2
OFF
ON
OFF
ON
SW1
OFF
ON
R
10 [k
]
Between pins 2 and 3
V
CC
1.4
[V]
200 [
A]
High impedance
Low impedance
High impedance
High impedance
When V
CC
= 9V (approx) R
28k
SW1
OFF
ON
Between pins 2 and 3
Low impedance
High impedance
(2) Control with pin 4 only
BA7755A
1
2
3
4
5
SW1
5V
R
V
CC
Fig. 2
Head
REC / EEE
EE (L)
REC (H)
Between pins 2 and 3
Low impedance
High impedance
(3) When used with the BA7751ALS
BA7755A
1
2
3
4
5
BA7751ALS
17
20
V
CC
REC / EE
Fig. 3
Head
4
Video ICs
BA7755A / BA7755AF
Application example
BA7755A
1
2
3
4
5
LINE IN
47
/ 16V
2
4
6
8
10
12
14
16
18
20
22
24
1
3
5
7
9
11
13
15
17
19
21
23
100
/ 16V
+
R
6
1000p
+ C
9
4.7
/ 25V
R
7
56k
C
12
33
/ 16V
+
10k
22k
10k
4.7
/ 25V
LINE OUT
+
4.7
/ 25V
+
EE
EE
SP
4.7
/ 25V
68k
68k
PB
REC
EP
MUTE ON
MUTE OFF
BA7751ALS
BIAS
PB
SW7
SW1
R
P
ALC DET.
ALC VR.
LINE
SW2
40dB
BIAS
BUFF.
SW5
SW4
SW3
REC
SW8
4.7
/ 25V
+
0.033
470
L
1
3.9mH
0.047
VR2
AC BIAS
51k
C
19
10
/ 16V
2.7k
47k
1M
+
47
/ 16V
22
/ 16V
PB IN REC OUT
+
10k
VR1
C
8
10
/ 16V
18k
12k
330k
0.01
220
33
/ 16V
4.7
/ 25V
47
1000p
1000p
V
CC
CTRL V
CC
C
16
C
18
R
12
R
10
R
8
R
13
C
15
R
16
C
7
C
6
C
10
R
15
R
19
C
20
R
14
C
21
C
17
R
9
C
14
C
13
C
4
C
5
R
4
R
1
C
1
R
2
R
3
R
5
C
2
C
3
+
+
+
+
+
5.6 k
26dB
R / P HEAD
Fig.4
Note:
R
13
, C
16
, R
16
and C
18
prevent switching
noise. These are not required if external
muting or some other method is used to
eliminate switching noise.
External dimensions (Units: mm)
SIP5
SOP8
BA7755A
BA7755AF
0.4
0.1
1.27
0.15
0.3Min.
0.15
0.1
0.11
6.2
0.3
4.4
0.2
5.0
0.2
8
5
4
1
1.5
0.1
2.54
9.6
0.5
3.5
0.5
4.9
0.2
1.2
0.6
1
1.3
0.8
0.6
5
11.8
0.2
0.3
0.1
2.4
0.2
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