9

Multimedia ICs

BA7726AS / BA7726AFS

(5) LPF

• Use the internal operational amplifier and an

attached capacitor and resistor to configure a tertiary

LPF for anti-aliasing and smoothing.

Cutoff frequency

LPF constant

Pass band gain

2kHz

22k

Ω

56k

Ω

47k

Ω

6800pF

4700pF

270pF

0.6dB

3kHz

18k

Ω

47k

Ω

39k

Ω

5600pF

3900pF

220pF

0.7dB

4kHz

15k

Ω

39k

Ω

33k

Ω

4700pF

3300pF

180pF

0.8dB

(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).

20

19

18

17

16

–

+

C3

R1

R3

C2

C1

R2

R1

C2

C1

R1

TO BU9252

FROM BU9252

Fig. 4 LPF

(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.

56789

LINE

LINE

C2

C1

LPF

+

–

IN L

IN R

TO OUTSW

Fig. 5 Vocal fader block

LPF constant examples

Cutoff frequency

LPF constant

100Hz

0.022

µF

0.1

µF

150Hz

0.015

µF

0.068

µF

200Hz

0.01

µF

0.047

µF

(7) ALC level

• When Vcc is 9.0V, ALC level can be set roughly

between -4dBV and +9dBV, and is determined by the

division between Vcc and the ground). ALC level is

calculated with the following equation, although slight

0

0

510

Set within this range

+ 10

+ 5

–5

–10

Pin 28 voltage: V28 (V)

at LINE OUT (f = 1kHz)

Fig. 6 ALC level vs. pin 28 voltage

are not guaranteed standards.

1.0

0.85

1

2

× 2 ×