TB2921AHQ
TOSHIBA Bi-CMOS Linear Integrated Circuit
Silicon Monolithic
TB2921AHQ
51 W
×
4-ch BTL Audio Power IC
The TB2921AHQ is a four-channel BTL power amplifier for car
audio applications.
This IC has a pure complementary P-ch and N-ch DMOS output
stage, offering maximum output power (P
OUT
MAX) of 5１ W.
It includes a standby switch, mute function, a high-side switch
and various protection features.
Features
•
High output power
•
•
•
•
•
•
•
•
•
•
•
•
P
OUT
MAX (1)
=
51 W (typ.)
(V
CC
=
15.2 V, f
=
1 kHz, JEITA max, R
L
=
4
Ω)
P
OUT
MAX (2)
=
45 W (typ.)
(V
CC
=
13.7 V, f
=
1 kHz, JEITA max, R
L
=
4
Ω)
P
OUT
MAX (3)
=
80 W (typ.)
(V
CC
=
14.4 V, f
=
1 kHz, JEITA max, R
L
=
4
Ω)
P
OUT
(1)
=
29 W (typ.)
(V
CC
=
14.4 V, f
=
1 kHz, THD
=
10%, R
L
=
4
Ω)
P
OUT
(2)
=
25 W (typ.)
(V
CC
=
13.2 V, f
=
1 kHz, THD
=
10%, R
L
=
4
Ω)
Weight: 7.7 g (typ.)
Low THD: 0.005% (typ.) (V
CC
=
13.2 V, f
=
1 kHz, P
OUT
=
5 W, R
L
=
4
Ω)
Low noise: V
NO
=
55
μVrms
(typ.)
(V
CC
=
13.2 V, R
g
=
0
Ω,
BW
=
20 Hz to 20 kHz, R
L
=
4
Ω)
Standby switch (pin 4)
Mute function (pin 22)
High-side switch (H-SW) (pin 25)
Various protection features
Thermal overload; overvoltage; output short-circuits to GND, V
CC
and across the load
Operating supply voltage : V
CC
(opr)
=
8.0 to 18 V (R
L
=
4
Ω)
: V
CC
(opr)
=
8.0 to 16 V (R
L
=
2
Ω)
Note 1: Install the device correctly. Otherwise, the device or system may be degraded, damaged or even destroyed.
Note 2: The protection features are intended to avoid output short-circuits or other abnormal conditions temporarily. It
is not guaranteed that they will prevent the IC from being damaged.
Exposure to conditions beyond the guaranteed operating ranges may not activate the protection features,
resulting in an IC damage due to output short-circuits.
Note 3: The protection circuit may malfunction depending on the connected speaker type due to a phase shift. The
operation of the device should therefore be verified by actually connecting a speaker to its outputs. It is not
recommended to connect a 2-ohm load such as a subwoofer that induces a significant phase shift, and that
special care should be taken in such cases.
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TB2921AHQ
Block Diagram
+B
C5
C2
10
Ripple
1
TAB
6
V
CC2
20
V
CC1
9
8
7
Out1 (+)
PW-GND1
Out1 (−)
C1
11
IN1
C1
12
IN2
5
2
Out2 (+)
PW-GND2
Out2 (−)
13 Pre-GND
3
C1
15
IN3
17
18
Out3 (+)
PW-GND3
C6
16 AC-GND
Out3 (−)
19
C1
14
IN4
21
24
Out4 (+)
PW-GND4
Out4 (−)
5V
Play
Mute
4 Stby
R1
C4
22 Mute
H-SW/short
23
25
Some of the functional blocks, circuits or constants may be omitted from the block diagram or simplified for
explanatory purposes.
C3
R
L
R
L
R
L
R
L
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TB2921AHQ
Detailed Description
1. Standby Switch
(pin 4)
The power supply can be turned on or off via
pin 4 (Stby). The threshold voltage of pin 4 is
set at about 3 V
BE
(typ.). The power supply
current is about 0.01
μA
(typ.) in the standby
state.
V
CC
ON
OFF
Power
4
10 kΩ
∼
2 V
BE
−
Standby Control Voltage (V
SB
): Pin 4
Standby
ON
OFF
Power
OFF
ON
V
SB
(V)
0 to 0.9
2.9 to Vcc
to Bias
filter network
Figure 1 Setting Pin 4 High Turns on
Power
Check the pop levels when the time constant of
pin 4 is changed.
Benefits of the Standby Switch
(1)
(2)
V
CC
can be directly turned on or off by a microcontroller, eliminating the need for a switching relay.
Since the control current is minuscule, a low-current-rated switching relay can be used.
Relay
Battery
High-current-rated switch
Battery
V
CC
V
CC
– Conventional Method –
From
microcontroller
Low-current-rated switch
Battery
From microcontroller
Battery
Standby
V
CC
Standby
– Using the Standby Switch –
V
CC
Figure 2 Standby Switch
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2009-02-03
TB2921AHQ
2. Mute Function
(pin 22)
The audio mute function is enabled by setting pin 22 Low. R
1
and C
4
determine the time constant of the
mute function. The time constant affects pop noise generated when power or the mute function is turned on
or off; thus, it must be determined on a per-application basis. (Refer to Figures 3 and 4.)
The value of the external pull-up resistor is determined, based on pop noise value.
For example, when the control voltage is changed from 5 V to 3.3 V, the pull-up resistor should be:
3.3 V / 5 V
×
47 kΩ
=
31 kΩ
ATT – V
MUTE
20
VCC
=
13.2 V
f
=
1 kHz
0
RL
=
4
Ω
VO
=
20dBm
−20
BW
=
400 Hz to 30 kHz
−40
−60
−80
−100
−120
0
5V
1 kΩ
Mute On/Off
control
R
1
22
C
4
Mute attenuation ATT
(dB)
0.5
1
1.5
2
2.5
3
Pin 22 control voltage: V
MUTE
(V)
Figure 3 Mute Function
Figure 4 Mute Attenuation
−
V
MUTE
(V)
3. High-Side Switch
Pin 25 of this device is used as a high-side switch to a V
CC
power supply, which is interlocked with a standby
pin. Thus, the power amplifier IC and the connected external unit (such as the hideaway unit) can be
simultaneously turned on or off by using the standby switch.
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TB2921AHQ
4. DC Offset Detection
It is possible to use this function by setting the voltage of Pin 22 higher than 8V.
In case of Appearing output offset voltage by Generating a Large Leakage Current on the input Capacitor etc.
V
Positive DC offset (+)
(caused by R
S1
)
V
CC
/2 (normal DC voltage)
Negative DC offset (−)
(caused by R
S2
)
V
ref
Leakage current
or short-circuit
R
S1
Elec. vol
R
S2
V
ref/2
V
bias
−
A
25
LPF
B
+
To a microcontroller
The microcontroller shuts down the
system if the output is lower than
the specified voltage.
Figure 5 DC Offset Detection Mechanism
Out(+)
Amp output
V
CC
/2
Offset detection
threshold voltage
Out(-)
GND
Time
Voltage at (A)
(pin 25)
GND
Time
Voltage at (B)
(LPF output)
GND
Time
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2009-02-03
Microcontroller MCU
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