8

Multimedia ICs

BA7725S / BA7725FS

A : Echo signal attenuation

B : Loop signal attenuation

C : Delay time

CCC

B

B

A

(dB)

(t)

Fig.8

Relationship between echo gain and loop gain

(4) Echo signal frequency characteristicis

The figure below shows the attenuation of signals out-

put from pin 1 when the audio signal is input to pin 22

(BA7725S) or pin 20 (BA7725FS). (This is the attenua-

tion when the input signal is output without being

passed through the BU9252S / F, and when the prima-

ry 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."

0

–10

–20

–30

– 40

– 50

100

1k

10k

100k

Sound source

Secondary echo signal

SIGNAL FREQUENCY : f (Hz)

Echo signal frequency

characteristics

Fig.9

Primary echo signal

SDIP22

SSOP-A20

19.4

± 0.3

0.5

± 0.1

1

11

12

22

0.3 ± 0.1

0

° ~ 15°

1.778

7.62

BA7725S

BA7725FS

11

10

20

1

8.7

± 0.2

0.36

± 0.1

0.8

0.3Min.

0.15