Muting Function - Toshiba TA8266HQ Description And Application Manual

Stand-By

3. Muting Function

(pin 22)
By means of controlling pin 22 less than 0.5 V, it can make the audio muting condition.
The muting time constant is decided by R
ON/OFF.
The series resistance; R1 must be set up less than 10 kΩ to get enough muting attenuation.
The muting function have to be controlled by a transistor, FET and micro-controller port which has
> 250 µA ability.
I
MUTE
Pin 22 terminal voltage has the temperature characteristics of 4.6 V (low temperature) to 3.2 V (high
temperature).
Therefore, it is need to design with attention as using the micro-controller of which operating voltage is
less than 5 V.
Terminal 22 may not be pulled up and shall be controlled by OPEN/LOW.
When it is obliged to do, it must be pulled up via diode, because it has to defend flowing reverse current
to internal circuit of pin 22.
<Recommended Application>
I (100 µA)
I
22
MUTE (OFF)
<Application for pulled up>
I (100 µA)
I
22
MUTE (OFF)
Figure 4 Muting Function
Large current capacity switch
BATTERY
V
CC
– Conventional Method –
Small current capacity switch
BATTERY
V
CC
– Stand-by Switch Method –
Figure 3
and C
1
A
R
1
I
MUTE
V
MUTE
R
1
I
MUTE
V
MUTE
Figure 5 Mute Attenuation − V
4
RELAY
V
CC
DIRECTLY FROM
MICROCOMPUTER
Stand-By V
CC
and these parts is related the pop noise at power
4
ATT – V
20
0
−20
−40
−60
−80
−100
0 0.4 0.8 1 1.2
Point A voltage: V MUTE (V)
TA8266HQ
BATTERY
FROM
MICROCOMPUTER
BATTERY
MUTE
10 kΩ 5 kΩ
V CC = 13.2 V
P o = 10 W
PL = 4 Ω
f = 1 kHz
1.6 2 2.4 2.8 3
(V)
MUTE
2006-04-28