BA7726AFS データシートの表示（PDF） - ROHM Semiconductor
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BA7726AFS Datasheet PDF : 11 Pages
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Multimedia ICs
(5) LPF
• Use the internal operational amplifier and an
attached capacitor and resistor to configure a tertiary
LPF for anti-aliasing and smoothing.
BA7726AS / BA7726AFS
C1
R1
C2
R3
C3
20 19 18 17
C2
TO BU9252
R1
FROM BU9252
R2 R1 C1
+–
16
LPF constant examples (VCC = 9.0V)
Fig. 4 LPF
LPF constant
Cutoff frequency
Pass band gain
R1
R2
R3
C1
C2
C3
2kHz
22kΩ
56kΩ
47kΩ
6800pF
4700pF
270pF
0.6dB
3kHz
18kΩ
47kΩ
39kΩ
5600pF
3900pF
220pF
0.7dB
4kHz
15kΩ
39kΩ
33kΩ
4700pF
3300pF
180pF
0.8dB
∗ CMP OUT (pin 20) output is positively correlated with Vcc. When Vcc is a voltage other than 9.0V, set the pass band gain so that maximum CMP side LPF output
(input to BU9252) is 5Vp-p. Make sure that the EXP side LPF constant does not exceed the load drive capability (minimum = 0.3mA, typical 0.5mA).
(6) Vocal fader function
• After the synchronous component of the left and
right channels is eliminated, LPF output is added to
the signal, which is then output (see figure below).
The vocal component is difficult to remove from cer-
tain types of sources.
–
+
TO OUTSW
LPF
between -4dBV and +9dBV, and is determined by the
voltage impressed on pin 28 (V28, set with resistive
division between Vcc and the ground). ALC level is
calculated with the following equation, although slight
error occurs as V28 approaches VCC.
VOAML Լ
1
2×
2
× (VCC – V28) [Vrms],
1.0 Ϲ V28 Ϲ 0.85 × (VCC – 1.0), at LINE OUT
56789
C1
LINE LINE
C2
IN R IN L
Fig. 5 Vocal fader block
+ 10
+5
VCC = 9.0V
at LINE OUT (f = 1kHz)
LPF constant examples
Cutoff frequency
LPF constant
C1
C2
100Hz
0.022µF
0.1µF
150Hz
0.015µF
0.068µF
200Hz
0.01µF
0.047µF
∗ C1 and C2 are only necessary when using the vocal fader function.
(7) ALC level
• When Vcc is 9.0V, ALC level can be set roughly
0
–5
Set within this range
– 10
0
5
10
Pin 28 voltage: V28 (V)
Fig. 6 ALC level vs. pin 28 voltage
∗ These figures are for standard samples and
are not guaranteed standards.
9
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