Rohm BA7725S Analog compander for karaoke echo system Datasheet

Multimedia ICs
Analog compander for KARAOKE
echo systems
BA7725S / BA7725FS
The BA7725S and BA7725FS are analog companders designed for KARAOKE echo systems, and logarithmically
compress the signal level by 1 / 2 and then logarithmically expand it by a factor of 2. These ICs can be used in combination with the BU9252S or BU9252F to create a digital echo system. These ICs have an internal line mixer amplifier for mixing line input and echo signals. The internal electronic volume control makes it possible to adjust the mixer
level and loop level mixer with an external DC voltage.
Applications
•Circuits
that require analog signal compression and expansion
•1)Features
Internal logarithmic 1 / 2 compression circuit and 2 ×
expansion circuit
2) Internal 2-channel buffer amplifier used as a tertiary
low pass filter
3) Internal mixer amplifier that mixes line input and
microphone input
4) Internal electronic volume control allows for adjustment of the echo mixer level and loop mixer level
using an external DC voltage.
5) Internal microphone amplifier and microphone input
ON / OFF switch
•Absolute maximum ratings (Ta = 25°C)
Parameter
Symbol
Limits
Unit
VCC
13
V
Power supply voltage
Power
dissipation
BA7725S
1000∗1
Pd
BA7725FS
600∗2
mW
Storage temperature
Tstg
– 55 ~ + 125
°C
Operating temperature
Topr
– 10 ~ + 70
°C
∗1 Reduced by 10mW for each increase in Ta of 1°C over 25°C.
∗2 Reduced by 6.0mW for each increase in Ta of 1°C over 25°C.
•Recommended operating conditions
Parameter
Power supply voltage
Symbol
Limits
Unit
VCC
6.5 ∼ 12.0
V
1
Multimedia ICs
BA7725S / BA7725FS
•Block diagram
BA7725S
BA7725FS
LINE IN
2
N.C.
3
22 MIC AMP IN
21 MIC AMP OUT
+
20 N.C.
LINE OUT
1
LINE IN
2
ECHO LEV CTRL
3
+
EXP BF OUT
9
5
EXP DET
6
16 CMP DET CT
EXP DET CT
7
15 CMP OUT
EXP BF OUT
8
EXP BF IN
9
17 CMP DET
14 CMP BF IN
2
16 CMP DET
15 CMP DET CT
14 CMP OUT
13 CMP BF IN
12 CMP BF OUT
BF
BF
EXP BF IN 10
DLY BF OUT 11
17 RIPPLE FILTER
BF
8
LOOP GAIN CTRL
18 RIPPLE FILTER
+
COMPRESS
EXP DET CT
4
BF
7
GND
EXPAND
EXP DET
18 VCC
VR
6
19 MIC AMP OUT
VR
LOOP GAIN CTRL
+
COMPRESS
5
EXPAND
GND
19 VCC
VR
4
+
+
VR
ECHO LEV CTRL
20 MIC AMP IN
SW
1
SW
LINE OUT
13 CMP BF OUT
BF
12 DLY BF IN
DLY BF OUT 10
BF
11 DLY BF IN
Multimedia ICs
BA7725S / BA7725FS
•Pin descriptions
Pin No.
BA7725S
BA7725FS
1
1
Pin name
Function
LINE OUT
Line output
Line input
2
2
LINE IN
3
—
N.C.
4
3
ECHO LEV CTRL
5
4
GND
Ground
Setting the loop damping ratio. Set between
2-9V (Vcc = 9.0V).
—
Microphone turns off when voltage drops below 1V.
Set echo signal damping ratio between 2-9V (Vcc = 9.0V).
6
5
LOOP GAIN CTRL
7
6
EXP DET
Expand detection
8
7
EXP DET CT
Setting expand attack / recovery time
Attack (R) = 5.6kΩ, recovery (R) = 85.6kΩ
9
8
EXP BF OUT
LPF BF output (expansion)
10
9
EXP BF IN
LPF BF input (expansion)
11
10
DLY BF OUT
Echo signal input BF output
12
11
DLY BF IN
Echo signal input BF input
13
12
CMP BF OUT
LPF BF output (compression)
14
13
CMP BF IN
LPF BF input (compression)
15
14
CMP OUT
Compression output
16
15
CMP DET CT
Setting the compression attack / recovery time
Attack (R) = 5.6kΩ, recovery (R) = 85.6kΩ
17
16
CMP DET
Compression detection
18
17
RIPPLE FITER
Attached ripple rejection capacitor
19
18
VCC
VCC
20
—
N.C.
21
19
MIC AMP OUT
Microphone amplifier output
22
20
MIC AMP IN
Microphone amplifier input
—
3
Multimedia ICs
BA7725S / BA7725FS
•Input / output circuits
Pin name
Pin No.
ECHO LEVEL
CTRL
4
Equivalent circuit
4
LOOP GAIN
CTRL
6
6
Note: The BA7725FS is mounted on a 20-pin SSOP-A package with a different pin number than the BA7725S.
On the BA7725FS, the ECHO LEVEL CTRL pin is pin 3, and the LOOP GAIN CTRL pin is pin 5.
4
Multimedia ICs
BA7725S / BA7725FS
•Electrical characteristics (unless otherwise noted, Ta = 25°C, Vcc = 9V)
Parameter
Supply current
Symbol
Min.
Typ.
Max.
Unit
ICC
4.3
5.7
7.6
mA
– 8.0
– 7.0
dBV
Conditions
No input
〈LINE THROUGH〉 INPUT : LINE IN, OUTPUT : LINE OUT
Line through output level
Line through output distortion
VOLL
– 9.0
THDLL
—
0.15
0.5
%
VIN = – 26.0dBV
VIN = – 26.0dBV, MIC OFF,∗1
Line through maximum output level
VOML
+ 5.0
+ 7.2
—
dBV
THD = 1%,∗1
Line through noise level
VONL
—
– 92
– 77
dBV
MIC OFF, Rg = 600Ω,∗2
dBV
〈MIC THROUGH〉 INPUT : MIC AMP IN, OUTPUT : LINE OUT
Microphone through output level
VOML
– 8.5
– 6.5
THDML
—
0.2
0.5
Microphone through input conversion noise
VONM
—
– 114
– 104
dBV
Input shorted
Microphone through crosstalk
CTML
—
– 91
– 75
dBV
VIN = – 44dBV, MIC OFF,∗2
– 6.5
– 4.5
– 2.5
dBV
VIN = – 52dBV
THDMC
—
0.5
2.0
Compress noise level
VONC
—
– 55
– 45
dBV
Rg = 600Ω,∗2
Compress characteristics
CMP
—
– 11.0
—
dB
VIN = – 42dBV → – 62dBV
Output level differential
– 9.7
—
dBV
VIN = – 5.0dBV, V4 = 9.0V
Microphone through output distortion
– 10.5
%
VIN = – 52dBV
VIN = – 52dBV,∗1
〈COMPRESS〉 INPUT : MIC AMP IN, OUTPUT : CMP BF OUT
Compress output level
Compress output distortion
VOMC
%
VIN = – 52dBV,∗1
〈EXPAND〉 INPUT : DLY BF IN, OUTPUT : LINE OUT
Expand output level 1
VODL1
– 11.7
Expand output distortion
THDDL
—
0.25
2.0
%
VIN = – 5.0dBV, V4 = 9.0V,∗1
Expand characteristic
EXP
—
– 19.5
—
dB
VIN = 0dBV → – 10.0dBV
Output level differential
Expand output level 2
VODL2
—
– 54
– 44
dB
VIN = – 5.0dBV,
V4 = 2.0V (VR = Min. time)
Output level differential relative to VoDL1
〈Loop〉 INPUT : DLY BF IN, OUTPUT : CMP BF OUT
Loop output level 1
VODC1
– 7.5
– 5.5
—
dBV
VIN = – 5.0dBV, V6 = 9.0V
Loop output level 2
VODC2
—
– 42
– 32
dBV
VIN = – 5.0dBV,
V6 = 2.0V (VR = Min. time)
Output level differential relative to VoDC1
MIC OFF holding voltage
V4OFF
0.0
—
1.0
V
—
MIC ON holding voltage
V4ON
2.0
—
9.0
V
—
〈Mode holding voltage〉
∗1
∗2
BW = 0.4-30kHz
DIN AUDIO
Unless otherwise noted, V4 = 9.0V (MIC ON), V6 = 9.0V (Max. LOOP GAIN)
5
Multimedia ICs
BA7725S / BA7725FS
•Measurement circuit
VCC 9V
R2
2.2k
+
MIC AMP IN
C1
1µ
R3
82k
22
21
C4
22µ
+
19
18
20
+
17
R35
10k
CMP BF OUT
C10 R11
R8
+
16
C32
0.1µ
C12
R9
C5
C6
0.1µ 0.47µ
15
14
COMPRESS
13
C33
12 0.1µ
10
11
DLY BF IN
R34
1k
BF
BF
VR
+
1
SW
2
C30 +
2.2µ
3
+
VR
4
EXPAND
5
6
7
9
R17
R33
1k
LINE
OUT
8
+
C20
0.1µ
R31
10k
BF
C20 C19
0.1µ 0.47µ
LINE
V4
IN
C15
R16
C18
R13
C14
V6
Fig.1
The above measurement circuit applies to a BA7725S mounted to a 22-pin SDIP package. A BA7725FS mounted to a 20pin SSOP-A package lacks N.C. pins 3 and 20; other than this
difference, the above circuit diagram applies.
Circuit operation
(1) MIC AMP IN / LINE OUT gain
Microphone amplifier gain (determined by R9 and R10) + line
amplifier gain (+12dB)
The audio signal is input via pin 22 (BA7725S) or pin 20
(BA7725FS) and amplified by the internal microphone amplifier, whose gain can be set with (attached) R9 and R10.
60
•
50
40
Open loop gain
Voltage (dB)
30
20
10
0
– 10
– 20
Note: Microphone amplifier gain must be set above +15dB.
– 30
1.5k
12k
MIC AMP IN
VIN
R9
+
22
Fig.3
+
BA7725S
1
SW
+
2
+
Fig.2
6
4 6 81 2
1M
4 6 81
10M
Microphone amplifier frequency
characteristics
+ 18dB
Microphone amplifier frequency
characteristic measurement circuit
2
100k
21
21
–
+
4 6 81
Frequency characteristic (Hz)
Vout
22
2
– 40
10k
R10
LINE OUT
LINE IN
Fig.4
Multimedia ICs
BA7725S / BA7725FS
(2) LINE IN / LINE OUT gain
Line amplifier gain is fixed at +18dB.
R9
+
MIC AMP IN
R10
22
21
1
SW
+
+
+12dB
2
+
LINE OUT
LINE IN
Fig.5
After being amplified by the internal microphone amplifier, the audio signal is logarithmically compressed by 1 / 2 then input to the tertiary low pass filter, which
comprises an internal BF and attached capacitor and resistor.
(3) Echo level control
The DC voltage supplied to pin 4 (BA7725S) or pin 3 (BA7725FS) determines
when the microphone switch is turned on and off and controls the echo level.
Microphone switch control
Mode
Threshold voltage
Operation
MIC OFF
L (1.0V Max.)
Only line audio is output.
MIC ON
H (2.0V Min.)
Line input and level-controlled microphone input are mixed and output.
Echo level control
Attenuation of the primary echo signals from sound
source can be controlled by changing the DC voltage
impressed on pin 4 (BA7725S) or pin 3 (BA7725FS)
between 2V and 9V.
Attenuation of primary echo signals can be controlled
by changing the DC voltage impressed on pin 6
(BA7725S) or pin 5 (BA7725FS) .
A TT (dB)
A TT (dB)
0
0
Primary echo
– 50
– 100
0
5
10
ECHO LEVEL CTRL pin voltage : (V)
Line output attenuation vs.
echo level control pin voltage
Fig.6
Line output attenuation : A TT (dB)
Line output attenuation : A TT (dB)
Sound source
Sound source
Primary echo
V4 = 9.0V
Secondary echo
– 50
– 100
0
5
10
LOOP GAIN CTRL pin voltage : (V)
Line output attenuation vs.
loop gain control pin voltage
Fig.7
7
Multimedia ICs
BA7725S / BA7725FS
Relationship between echo gain and loop gain
(dB)
A
B
B
A : Echo signal attenuation
(t)
B : Loop signal attenuation
C : Delay time
C
C
C
Fig.8
LINE OUTPUT ATTENUATION : A TT (dB) —
(4) Echo signal frequency characteristicis
The figure below shows the attenuation of signals output from pin 1 when the audio signal is input to pin 22
(BA7725S) or pin 20 (BA7725FS). (This is the attenuation when the input signal is output without being
passed through the BU9252S / F, and when the primary and secondary echo signals are passed through an
attached low pass filter with the same constant shown
in "Application example," and then processed by the
BU9252S / F delay circuit.)
Note: These are the values when using the constant shown in "Application
example."
Sound source
0
Primary echo signal
– 10
Secondary echo signal
– 20
– 30
– 40
3pin, 5pin = VCC (VR : Max.)
– 50
100
1k
10k
100k
SIGNAL FREQUENCY : f (Hz)
Echo signal frequency
characteristics
•External dimensions (Units: mm)
Fig.9
BA7725S
BA7725FS
8.7 ± 0.2
19.4 ± 0.3
1.778
0.5 ± 0.1
0° ~ 15°
11
1
10
0.8
0.36 ± 0.1
0.15 ± 0.1
7.8 ± 0.3
0.3 ± 0.1
1.8 ± 0.1
7.62
0.11
11
1
20
5.4 ± 0.2
12
6.5 ± 0.3
0.51Min.
3.4 ± 0.2 3.95 ± 0.3
22
0.3Min.
0.15
SDIP22
8
SSOP-A20
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