ROHM BA7781K Datasheet
1
Video ICs
Stereo microphone amplifier for camcorders
BA7781K
The BA7781K allows construction of a stereo-microphone amplifier for camcorder use with a minimum number of
external components. The IC has a built-in wind-noise detection circuit, and wind-noise rejection filter. The filter circuit is controlled automatically. The IC can operate off a 3.0V power supply.
•
Applications
Camcorders
•
Features
1) Operates off a 3.0V to 5.25V power supply.
2) Automatic wind-noise rejection circuit.
3) Matrix circuit for stereo emphasis.
4) Automatic switching circuit for external microphones, built-in external monaural decision circuit,
and input switch mode decision circuit.
•
Block diagram
04 05 06
24
23
22
18 17
16
15
14
12
11
09
25
26
27
28
29
30
31
32
13
10
01
02
03 07 08
21 20 19
EXT IN L
BG
INT IN L
GND
VREG
INT IN R
RIPL
EXT IN R
DET OUT
DET IN
BIAS
V
CC
LPF INV OUT
LPF INV IN
MIX OUT
MIC MONO
MODE 24
PRE OUT L
INV IN L
INV OUT L
MTX IN L
MTX OUT L
HPF IN L
OUT L
MODE 1
PRE OUT R
INV IN R
INV OUT R
MTX IN R
MTX OUT R
HPF IN R
OUT R
EXT
INT
13dB
13dB
GND
REG
BIAS
INT
EXT
+
–
NOR
WND
NOR
WND
15dB
–
EXT
EXT
BIAS
V
CC
MIX
+
–
10dB
15dB
–
+
DET
+
2
Video ICs BA7781K
•
Absolute maximum ratings (Ta = 25°C)
Parameter
Symbol Limits Unit
V
CC
7.0 V
Pd mW
Topr °C
Tstg °C
400
∗
– 10 ~ +70
– 55 ~ +125
∗
Reduced by 4mW for each increase in Ta of 1°C over 25°C.
Power supply voltage
Power dissipation
Operating temperature
Storage temperature
•
Recommended operating conditions (Ta = 25°C)
Parameter Symbol Min. Typ. Max. Unit
V
CCS
3.0 — 5.25 VPower supply voltage
•
Electrical characteristics (unless otherwise noted, Ta = 25°C and VCC = 3.3V)
Parameter
Symbol Min. Typ. Max. Unit
I
INT
— 5.0 8.0 mA
I
EXT
— 4.8 8.0 mA
VG
PR
12 13 14 dB
VG
OA
14 15 16 dB
THD — 0.05 0.3 %
V
om 0.85 1.1 — Vrms
VNO — – 90 – 80 dBV
CT
I
→E
— – 88 – 70 dB
— – 61 – 50 dB
V
REG
2.3 2.5 2.75 V
V
HSWH
1.6 — VCC V
V
HSWL
0 — 0.6 V
VG
HON
— — – 30 dB
VG
HOFF
— — – 30 dB
V
HON
2.5 — V
V
HOFF
0 — 0.3 V
CT
L←
→R
Conditions
V
CC
INT MIC IN, L / Rch
EXT MIC IN, L / Rch
30 / 32pin→2pin GAIN
27 / 25pin→23pin GAIN
3 / 6 / 7pin→8pin GAIN
22 / 19 / 18pin→17pin GAIN
INT / EXT, Vo = 300mV
rms, L / Rch
∗
2
INT / EXT MIC IN, L / Rch
INT / EXT, L / Rch, R
g = 1kΩ
INT / EXT MIC, Lch→Rch, R
g = 1kΩ
15pin – 29.0dBV IN (80Hz)
6 / 19pin – 25.5dBV IN (1kHz)
6→8pin / 19→17pin GAIN
15pin – 45.0dBV IN (80Hz)
7 / 18pin – 25.5dBV IN (1kHz)
7→8pin / 18→17pin GAIN
INT→EXT MIC IN, R
g = 1kΩ, L / Rch
Current dissipation 1
Current dissipation 2
Preamplifier gain
Output amplifier gain
Distortion
Maximum output voltage
Output noise voltage
Input switch separation
Interchannel separation
Internal microphone power supply voltage
Input switch control voltage
High-pass filter switching
attenuation characteristic
High-pass filter control voltage
∗
1 JIS-A filter used.
∗
2 400Hz to 30kHz filter used.
No dissipation by mic
No dissipation by mic
f = 1kHz (distortion 1%
∗
2
)
When gain is 28dB
∗
1
(distortion 1%
∗
2
) , when gain is 28dB
∗
1
(distortion 1%
∗
2
) , when gain is 28dB
∗
1
Pin 27 output voltage for 30kΩ load
“H”level, 1 / 24 pin DC
“L” level, 1 / 24 pin DC
Input 80Hz signal to pin 15, and
measure gain at switch off side.
∗
1
HPF on holding voltage (pin 16)
HPF off holding voltage (pin 16)
3
Video ICs BA7781K
1 MODE 1
—
25kΩ
2 PRE OUT R 1.65
3 INV IN R 1.65 100kΩ
4 INV OUT R 1.65
5 MTX IN R 1.65 B
6 MTX OUT R 1.65
7 HPF IN R 1.65 100kΩ
8 OUT R 1.65
9 MIC MONO — C
10 MIX OUT 1.65
11 LPF INV IN — B
12 LPF INV OUT —
13 V
CC
3.3 —
14 BIAS 1.65
15 DET IN 1.65 2kΩ
16 DET OUT — 22kΩ
17 OUT L 1.65
18 HPF IN L 1.65 100kΩ
19 MTX OUT L 1.65
20 MTX IN L 1.65 B
21 INV OUT L 1.65
22 INV IN L 1.65 100kΩ
23 PRE OUT L 1.65
24 MODE 24 — 25kΩ
25 EXT IN L 1.65 75kΩ
26 BG 1.25 10kΩ
27 INT IN L 1.65 75kΩ
28 GND ——
29 VREG 2.5 C
30 INT IN R 1.65 75kΩ
31 RIPL 1.65 50kΩ
32 EXT IN R 1.65 75kΩ
EF (P - P)
EF (P - P)
EF (P - P)
C (P - P)
EF (P - P)
EF (P - P)
EF (P - P)
C (P - P)
EF (P - P)
EF (P - P)
EF (P - P)
Pin name FunctionPin No. Voltage (
V)
∗
EF: emitter follower, P-P: push pull, B: base, and C: collector.
Circuit
Mode control 1 input
Preamplifier output
Inverter input
Inverter output
Matrix amplifier input
Matrix amplifier output
High-pass filter input
Signal output
External microphone monaural decision signal output
Mix Output
Low-pass filter block inverter input
Low-pass filter block inverter output
V
CC
Bias voltage
Detector circuit input
Detector circuit output
Signal output
High-pass filter input
Matrix amplifier output
Matrix amplifier input
Inverter output
Inverter input
Preamplifier output
Mode control 24 input
External microphone input
For regulator ripple filter capacitor
Internal microphone input
GND
Regulator output
Internal microphone input
For bias ripple filter capacitor
External microphone input
All numerical values are standardized values.
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Pin descriptions
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