TB2903HQ
Block Diagram
C
5
1
TAB
20
V
CC1
6
V
CC2
OUT1 (+)
9
C
1
11
IN1
PW-GND1 8
OUT1 (−)
7
R
L
OUT2 (+)
12
IN2
5
R
L
C
1
PW-GND2 2
OUT2 (−)
3
C
6
16 AC-GND
OUT3 (+)
15
IN3
17
R
L
C
1
PW-GND3 18
OUT3 (−)
19
OUT4 (+)
14
IN4
21
R
L
C
1
PW-GND4 24
OUT4 (−)
23
PRE-GND
13
RIP
10
C
2
STBY
4
Off-set
DET
25
MUTE
22
PLAY
C
4
R
1
MUTE
: PRE-GND
: PW-GND
5V
Note4:
Some of the functional blocks, circuits, or constants in the block diagram may be omitted or simplified for
explanatory purpose.
C
3
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TB2903HQ
Caution and Application Method
(Description is made only on the single channel.)
1. Voltage Gain Adjustment
This IC has no NF (negative feedback) Pins. Therefore, the voltage gain can not be adjusted, but it makes
the device a space and total costs saver.
Amp. 2A
Amp. 1
Input
Amp. 2B
Figure 1
Block Diagram
The voltage gain of amp.1
: G
V1
=
0dB
The voltage gain of amp.2A, B
: G
V2
=
20dB
The voltage gain of BTL connection : G
V (BTL)
=
6dB
Therefore, the total voltage gain is decided by expression below.
G
V
=
G
V1
+
G
V2
+
G
V (BTL)
=
0
+
20
+
6
=
26dB
2. Standby SW Function
(pin 4)
By means of controlling pin 4 (standby pin) to
High and Low, the power supply can be set to ON
and OFF. The threshold voltage of pin 4 is set at
about 3V
BE
(typ.), and the power supply current is
about 2
µA
(typ.) in the standby state.
V
CC
ON
OFF
Power
4
10 kΩ
≈
2 V
BE
to BIAS
CUTTING CIRCUIT
Control Voltage of Pin 4: V
SB
Standby
ON
OFF
Power
OFF
ON
V
SB
(V)
0~1.5
3.5~6 V
When changing the time constant of pin 4, check the
pop noise.
Figure 2 With pin 4 set to High,
Power is turned ON
Advantage of Standby SW
(1)
(2)
Since V
CC
can directly be controlled to ON or OFF by the microcomputer, the switching relay can be
omitted.
Since the control current is microscopic, the switching relay of small current capacity is satisfactory
for switching.
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TB2903HQ
Large current capacity switch
Battery
Relay
Battery
V
CC
V
CC
– Conventional Method –
From
microcomputer
Small current capacity switch
Battery
From microcomputer
Battery
Stand-By V
CC
Stand-By V
CC
– Standby Switch Method –
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 R
1
and C
4,
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.
Moreover, this terminal (pin 22) serves as the source switch of current of an internal mute circuit. And it is
designed so that the discharge current of this terminal (pin 22) may serve as 200
µA.
The outside pull-up
resistor R
1
is determind 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
To obtain enough mute attenuation, a series resistor, R
1
at pin 22 should be 47 kΩ or more.
ATT – V
MUTE
20
0
V
CC
=
13.2 V
f
=
1kHz
R
L
=
4
Ω
V
OUT
=
20dBm
(dB)
Mute attenuation ATT
−20
−40
−60
−80
−100
−120
0
5V
1 kΩ
Mute ON/OFF
control
R
1
22
C
4
0.5
1
1.5
2
2.5
3
Pin 22 control voltage: VMUTE (V)
Figure 4
Muting Function
Figure 5
Mute Attenuation
−
V
MUTE
(V)
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TB2903HQ
4. Off-set detection function
In case of Appearing output offset voltage by Generating a Large Leakage Current on the input
Capacitor etc.
V
DC Voltage (+) Amp (at leak) (R
S1
)
V
CC/2
(normal DC voltage)
V
ref
Leak or short
R
S1
Elec. vol
R
S2
−
V
bias
25
A
L.P.F.
B
To CPU
5V
V
ref/2
+
DC Voltage (−) Amp (at short) (R
S2
)
Offset voltage (at leak or short)
Figure 6
Application and Detection Mechanism
Threshold level (R
S1
)
(+) Amp output
V
CC/2
Threshold level (R
S2
)
GND
t
Voltage of
point (A)
GND
t
Voltage of
point (B)
GND
R
S2
t
Figure 7 Wave Form
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2004-07-25
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