Rohm BA7781 Stereo microphone amplifier for camcorder Datasheet

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
•1)Features
Operates off a 3.0V to 5.25V power supply.
4) Automatic switching circuit for external microphones, built-in external monaural decision circuit,
and input switch mode decision circuit.
2) Automatic wind-noise rejection circuit.
3) Matrix circuit for stereo emphasis.
INV IN L
INV OUT L
MTX IN L
MTX OUT L
HPF IN L
OUT L
23
22
21
20
19
18
17
–
+
13dB
INT IN L 27
GND
16 DET OUT
15 DET IN
14 BIAS
EXT
+
– MIX
REG
GND 28
15dB
DET
BG 26
INT
WND
PRE OUT L
24
EXT IN L 25 EXT
NOR
MODE 24
•Block diagram
BIAS
VCC
10dB
VREG 29
13 VCC
12 LPF INV OUT
RIPL 31
INT
11 LPF INV IN
EXT
10 MIX OUT
13dB
+
–
09 MIC MONO
01
02
03
04
05
06
07
08
PRE OUT R
INV IN R
INV OUT R
MTX IN R
MTX OUT R
HPF IN R
OUT R
15dB
MODE 1
EXT IN R 32 EXT
NOR
WND
INT IN R 30
BIAS
+ –
1
Video ICs
BA7781K
•Absolute maximum ratings (Ta = 25°C)
Parameter
Symbol
Limits
Unit
Power supply voltage
VCC
7.0
V
Power dissipation
Pd
400∗
mW
Operating temperature
Topr
– 10 ~ +70
°C
Storage temperature
Tstg
– 55 ~ +125
°C
∗ Reduced by 4mW for each increase in Ta of 1°C over 25°C.
•Recommended operating conditions (Ta = 25°C)
Parameter
Symbol
Min.
Typ.
Max.
Unit
VCCS
3.0
—
5.25
V
Power supply voltage
•Electrical characteristics (unless otherwise noted, Ta = 25°C and V
Parameter
Symbol
Min.
Typ.
CC
Max.
= 3.3V)
Unit
Conditions
Current dissipation 1
I INT
—
5.0
8.0
mA
INT MIC IN, L / Rch
No dissipation by mic
Current dissipation 2
IEXT
—
4.8
8.0
mA
EXT MIC IN, L / Rch
No dissipation by mic
Preamplifier gain
VGPR
12
13
14
dB
30 / 32pin→2pin GAIN
27 / 25pin→23pin GAIN
Output amplifier gain
VGOA
14
15
16
dB
3 / 6 / 7pin→8pin GAIN
22 / 19 / 18pin→17pin GAIN
Distortion
THD
—
0.05
0.3
%
INT / EXT, Vo = 300mVrms, L / Rch∗2
Maximum output voltage
Vom
0.85
1.1
—
Vrms
INT / EXT MIC IN, L / Rch
f = 1kHz (distortion 1%∗2 )
Output noise voltage
VNO
—
– 90
– 80
dBV
INT / EXT, L / Rch, Rg = 1kΩ
When gain is 28dB∗1
Input switch separation
CTI→E
—
– 88
– 70
dB
INT→EXT MIC IN, Rg = 1kΩ, L / Rch
(distortion 1%∗2 ) , when gain is 28dB∗1
—
– 61
– 50
dB
INT / EXT MIC, Lch→Rch, Rg = 1kΩ
(distortion 1%∗2 ) , when gain is 28dB∗1
VREG
2.3
2.5
2.75
V
Pin 27 output voltage for 30kΩ load
VHSWH
1.6
—
VCC
V
“H”level, 1 / 24 pin DC
VHSWL
0
—
0.6
V
“L” level, 1 / 24 pin DC
Interchannel separation
Internal microphone power supply voltage
Input switch control voltage
CTL←
→R
Input 80Hz signal to pin 15, and
measure gain at switch off side.∗1
High-pass filter switching
attenuation characteristic
High-pass filter control voltage
∗1 JIS-A filter used.
∗2 400Hz to 30kHz filter used.
2
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
VGHON
—
—
– 30
dB
VGHOFF
—
—
– 30
dB
VHON
2.5
—
VCC
V
HPF on holding voltage (pin 16)
VHOFF
0
—
0.3
V
HPF off holding voltage (pin 16)
Video ICs
BA7781K
•Pin descriptions
Pin No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
Pin name
MODE 1
PRE OUT R
INV IN R
INV OUT R
MTX IN R
MTX OUT R
HPF IN R
OUT R
MIC MONO
MIX OUT
LPF INV IN
LPF INV OUT
VCC
BIAS
DET IN
DET OUT
OUT L
HPF IN L
MTX OUT L
MTX IN L
INV OUT L
INV IN L
PRE OUT L
MODE 24
EXT IN L
BG
INT IN L
GND
VREG
INT IN R
RIPL
EXT IN R
Function
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
VCC
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
Voltage (V)
—
1.65
1.65
1.65
1.65
1.65
1.65
1.65
—
1.65
—
—
3.3
1.65
1.65
—
1.65
1.65
1.65
1.65
1.65
1.65
1.65
—
1.65
1.25
1.65
—
2.5
1.65
1.65
1.65
Circuit
25kΩ
EF (P - P)
100kΩ
EF (P - P)
B
EF (P - P)
100kΩ
C (P - P)
C
EF (P - P)
B
EF (P - P)
—
EF (P - P)
2kΩ
22kΩ
C (P - P)
100kΩ
EF (P - P)
B
EF (P - P)
100kΩ
EF (P - P)
25kΩ
75kΩ
10kΩ
75kΩ
—
C
75kΩ
50kΩ
75kΩ
∗ EF: emitter follower, P-P: push pull, B: base, and C: collector.
All numerical values are standardized values.
3
Video ICs
BA7781K
•Measurement circuit
MODE 24
HPF IN
SW2
1
10k 10.5k
0.1µ
2
2200p
0.1µ
0.1µ
Lch
26
EXT
INT
20
19
18
–
+
15dB
13dB
10µ
28
GND
30k
10µ
EXT IN
0.1µ
+
10µ
VCC
13
12
BIAS
+
–
200k
31
INT
+
–
2
200k 0.1µ
INV (11) IN
10
13dB
32 EXT
1
11
EXT
3
NOR
WND
Rch
1M
0.1µ
BIAS
VCC
10dB
29
30
+
15
L OUT
14
0.1µ
INT IN
16
EXT
+ MIX
–
GND
27
0.1µ
REG
INT IN
2.2µ
+
17
DET
+
21
NOR
25
22
WND
0.1µ
EXT IN
23
24
5
4
6
9
15dB
8
7
0.1µ
0.1µ
R OUT
2200p
0.1µ
10k 10.5k
1
2
SW1
MODE 1
HPF IN
Fig. 1
4
UNITS
RESISTOR: Ω
CAPACITOR: F
Video ICs
BA7781K
•Application example
UNITS
RESISTOR: Ω
CAPACITOR: F
B'
A' 15k
2200p
10k
0.1µ
0.022µ 100k
10.5k
0.1µ
L OUT
0.022µ
2.2µ
26
20
19
–
+
EXT
INT
18
+
24k
17
15dB
16
1M
13dB
DET
L ch
21
NOR
25
+
22
WND
EXT IN
23
24
0.1µ
15
10µ
28
BIAS
VCC
10dB
GND
+
–
220k
32
INT
100k
13dB
0.1µ
2
3
0.1µ
0.01µ
5
4
0.1µ
6
MIC-MONO
24k
8
7
0.01µ
9
15dB
0.022µ
10k 10.5k 0.022µ 100k
A
150k
100k
+
–
EXT
1
11
WND
10µ
EXT IN
VCC
2200p
10
NOR
31
EXT
BIAS
30
+
R ch
10µ
13
12
29
0.1µ
INT IN
+
14
EXT
+ MIX
–
GND
27
0.1µ
REG
INT IN
R OUT
2200p
B 15k
Additional components INT / EXT monitoring
INT / EXT
L OPEN
100k
12
+
1µ
∗1) When using the matrix circuit connect A-A' and B-B'.
∗2) The pin 10 and 12 low-pass filter components are for fc = 150Hz, Gain = 0dB, 18dB / oct.
Fig. 2
5
Video ICs
BA7781K
•Measurement circuit switch table (blank cells: no spesification)
SW1
SW2
MODE1
MODE24
Current dissipation 1
1
1
H
L
Current dissipation 2
1
1
Preamplifier gain
1
1
Output amplifier gain
1
1
Distortion
1
1
Maximum output
1
1
Output noise voltage
1
1
Input switch separation (INT→ EXT)
1
1
L
L
INT
INT
1
1
H
L
INT
EXT
1
1
L
L
EXT
1
1
1
1
H
Vth
1
1
Vth
L
INT, EXT
2
2
H
L
INV (11) , HPF
1
1
H
L
INV (11) , INT
1
1
H
L
INV, 16pin of Vth
2
2
H
L
HPF, 16pin of Vth
Parameter
Interchannel separation
Internal microphone power supply voltage
Input switch control voltage
High-pass filter switching attenuation characteristic
High-pass filter control voltage
Signal input pin
Conditions other than No. 1
INT, EXT
∗ H and L are VCC and GND levels.
Measure the voltage range that maintains the mode for Vth.
notes
•(1)Operation
Automatic wind-noise rejection circuit
The MAX OUT (pin 10) signal passes through the
three-stage low-pass filter connected between pins 10
and 12, and the DC level of the low-frequency signal
component is detected. This DC voltage (pin 16 DC
voltage) automatically controls the on / off switching of
the high-pass filter. The components connected to pins
11 and 12 set the gain of a multiple-feedback-type twostage low-pass filter constructed around an inverting
amplifier, and by changing the gain of the circuit you
can adjust the detection sensitivity.
It is also possible to switch the high-pass filter manually
by applying a DC voltage to pin 16 (see Fig 2).
6
(2) Additional compornents for INT / EXT monitor use
An internal circuit sets pin 12 to roughly the bias potential in INT mode, and to GND for EXT mode. This
switches the external transistor on and off for INT and
EXT modes respectively. This can be used to indicate
whether the microphone amplifier is operating with the
INT or EXT input. In the case of a camcorder, this can
be used to display a massage such as “EXT MIC ON”
in the EVF.
Video ICs
BA7781K
VCC = 3.3V
Input: 80Hz
Ta = 25°C
16PIN DETECT OUTPUT: VDETOUT (V)
OUTPUT LEVEL: VROUT (dBV)
•Electrical characteristic curves
0
– 20
HPF side output
7→8pin
NOR side output
6→8pin
– 40
– 60
– 60
– 50
– 40
– 30
– 20
VCC = 3.3V
Input: 80Hz
Ta = 25°C
2.5
2.0
1.5
1.0
0.5
0
– 60
– 10
– 50
– 40
– 30
– 20
– 10
15PIN INPUT SIGNAL LEVEL: VDETIN (dBV)
15PIN INPUT SIGNAL LEVEL: VDETIN (dBV)
Fig. 4 Detector voltage characteristis
Fig. 3 HPF switching characteristics
•External dimensions (Units: mm)
9.0 ± 0.3
7.0 ± 0.2
16
32
9
1.45 ± 0.1
1
0.05
17
25
0.8
8
0.4
7.0 ± 0.2
9.0 ± 0.3
24
0.15 ± 0.1
0.4 ± 0.1
0.15
QFP32
7
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