5

Multimedia ICs

BU9253AS / BU9253FS / BU9255FS

• When switching between the muted and unmuted

state (pin 15 (pin 17) L

→M→H), the pin 15 (pin 17) M

time should be longer than one SRAM cycle. This is to

assure stability by initializing the SRAM before mode

switching.

Note: Figures in parentheses ( ) are for BU9253AS.

(2) Differences between BU9253AS / FS and BU9255FS

There is a difference regarding the signal stopping for

muting. With BU9253AS / FS, the output from pin 8 (pin

9) is stopped during muting. With BU9255FS, the output

from pin 5 is stopped during muting.

100

µ

0.1

µ

0.01

µ

0.012

µ

20k

20k

8.2k

IN

4700p

10k

100p

39k

MUTE

MIX

2.2

µ

2.2

µ

RESISTOR : [

Ω]

Unit

CAPACITOR: [F]

OUT

3300p

15k

10k

4.7k

0.01

µ

0.01

µ

22

µ

ECHO LEVEL

12345678

0.47

µ

D / A

SRAM

A / D

OSC

16

15

14

13

12

11

10

9

COUNTER

Fig. 2

+

–

+

–

+

+

+

(1) Mute control functions

H

Unmuted (operating state)

M

Muted

L

Clock stop and muted

Pin 15 voltage (pin 17)

Mode