BH3868BFS Datasheet, PDF (19/28 Pages) Rohm – Audio sound processor with BBE

Audio ICs
BH3868BFS
(2) Setting of Attack Time and Release Time
In this IC, the Attack Time and Release Time can be set in the boost side and cut side of AGC separately.
430
RR1
20k
RR2
2
LS1
C1
RL1
1µ
1Meg
3
LS2
C2
RL2
1µ
1Meg
Detector circuit of suppression
Attack Time
: RR1 × C1
Recovery Time : RL1 × C1
Detector circuit of amplification
Attack Time
: RR2 × C2
Recovery Time : RL2 × C2
The Attack Time and Recovery Time shall be set by a resistor in IC and external capacitor and resistor. The internal
resistance is RR1=430Ω and RR2=20KΩ (Typ).
If the constant of capacitor C2 of LS2 decreases, an amplification starting point is shifted in a direction of smaller input
voltage. Moreover, the distortion rate also changes and becomes worse.
If the constant of capacitor C1 of LS1C1 decreases, the distortion rate becomes worse. If the resistance value of RL1
increases, the suppression is reduced.
!SURROUND
(1) Setting of Frequency Characteristic
This IC has an output terminal (4pin) for the surround signal. The surround characteristic can be varied by adding an
appropriate filter to this terminal. An example of characteristic that low-pass filter has been set is shown below :
+
10k
SOUT
4
+
−
R1
−
f1 =
1
2πCR2
0.0047µ
C
4.7k
R2
An amplifier to define the sound effect.
f2
=
1
2πC(R1 +
R2)
A1 =
R2
R1 + R2
A2 = 1
A2
A1
f2
f1
Frequency [Hz]
19/27