ROHM BA7725S, BA7725FS Datasheet
1
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
•
Features
1) 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
Power supply voltage V
CC 13 V
Power
dissipation
BA7725S 1000
∗
1
mW
600
∗
2
BA7725FS
Storage temperature °C
Operating temperature °C
– 55 ~ + 125
– 10 ~ + 70
Pd
Tstg
Topr
∗
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 Symbol Limits Unit
Power supply voltage VV
CC 6.5 ∼ 12.0
2
Multimedia ICs BA7725S / BA7725FS
•
Block diagram
BA7725S BA7725FS
22
21
20
19
18
17
16
15
14
13
12
10
9
8
7
6
5
4
3
2
1
20
19
18
17
16
15
14
13
12
11
11
1
2
3
4
5
6
7
8
9
10
SW VR
VR
BF
EXPAND
BF
BF
BF
BF
EXPAND
VR
VRSW
MIC AMP IN
MIC AMP OUT
N.C.N.C.
GND
GND
DLY BF OUT
EXP BF IN
EXP BF OUT
EXP DET CT
EXP DET
LOOP GAIN CTRL
ECHO LEV CTRL
LINE IN
LINE OUT
COMPRESS
COMPRESS
RIPPLE FILTER
CMP DET
CMP DET CT
CMP OUT
CMP BF IN
CMP BF OUT
DLY BF IN
LINE OUT
LINE IN
ECHO LEV CTRL
LOOP GAIN CTRL
EXP DET
EXP DET CT
EXP BF OUT
EXP BF IN
DLY BF OUT
MIC AMP IN
MIC AMP OUT
RIPPLE FILTER
CMP DET
CMP DET CT
CMP OUT
CMP BF IN
CMP BF OUT
DLY BF IN
VCC
+
+
+
+
+
+
VCC
BF
3
Multimedia ICs BA7725S / BA7725FS
•
Pin descriptions
Pin name Function
BA7725S BA7725FS
1 1 LINE OUT Line output
2 2 LINE IN Line input
3— —
—
N.C.
4 3 ECHO LEV CTRL
Microphone turns off when voltage drops below 1V.
Set echo signal damping ratio between 2-9V (Vcc = 9.0V).
5 4 GND Ground
6 5 LOOP GAIN CTRL
Setting the loop damping ratio. Set between
2-9V (Vcc = 9.0V).
7 6 EXP DET Expand detection
8 7 EXP DET CT
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
17 16 CMP DET Compression detection
18 17 RIPPLE FITER Attached ripple rejection capacitor
19 18
20 — N.C.
21 19 MIC AMP OUT Microphone amplifier output
22 20 MIC AMP IN Microphone amplifier input
Setting expand attack / recovery time
Attack (R) = 5.6kΩ, recovery (R) = 85.6kΩ
Setting the compression attack / recovery time
Attack (R) = 5.6kΩ, recovery (R) = 85.6kΩ
V
CCVCC
Pin No.
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