TB2904HO 데이터 시트보기 (PDF) - Toshiba
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TB2904HO Datasheet PDF : 16 Pages
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Large current capacity switch
Battery
VCC
VCC
– Conventional Method –
TB2904HQ(o)
Relay
Battery
From
microcomputer
Small current capacity switch From microcomputer
Battery
Stand-By VCC
Stand-By VCC
– Standby Switch Method –
Battery
Figure 3
3. Muting Function (pin 22)
Audio muting function is enabled when pin 22 is Low. When the time constant of the muting function is
determined by R1 and C4, it should take into account the pop noise. The pop noise, which is generated when
the power or muting function is turned ON/OFF, will vary according to the time constant. (Refer to Figure 4
and Figure 5.)
The pin 22 is designed to operate off 5 V so that the outside pull-up resistor R1 is determined on the basic
of this value:
ex) When control voltage is changed in to 6 V from 5 V.
6 V/5 V × 47 k = 56 k
Additionally, as the VCC is rapidly falling, the IC internal low voltage muting operates to eliminate the
large pop noise basically.
The low voltage muting circuit pull 200 µA current into the IC so that the effect of the internal low
voltage muting does not become enough if the R1 is too small value.
To obtain enough operation of the internal low voltage muting, a series resistor, R1 at pin 22 should be
47 kΩ or more.
5V
22
R1
C4
1 kΩ
Mute ON/OFF
control
Figure 4 Muting Function
ATT – VMUTE
20
VCC = 13.2 V
f = 1 kHz
0 RL = 4 Ω
Vout = 7.75 Vrms
(20dBm)
−20
−40
−60
−80
−100
−120
0
0.5
1
1.5
2
2.5
3
3.5
Pin 22 control voltage: VMUTE (V)
Figure 5 Mute Attenuation − VMUTE (V)
4
2004-03-26
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