TB2921HQ
TOSHIBA Bi-CMOS Linear Integrated Circuit
Silicon Monolithic
TB2921HQ
(preliminary)
Maximum Power 50 W BTL × 4-ch Audio Power IC
The TB2921HQ is 4-ch BTL audio amplifier for car audio
applications.
This IC can generate higher power: P
OUT
MAX =50 W as it
includes the pure complementary P-ch and N-ch DMOS output
stage.
It is designed to yield low distortion ratio for 4-ch BTL audio
power amplifier, built-in standby function, muting function, and
various kinds of protectors.
Additionally, high-side switch is built in.
Weight: 7.7 g (typ.)
Features
•
High power output
: P
OUT
MAX (1) = 50 W (typ.)
(V
CC
= 15.2 V, f = 1 kHz, JEITA max, R
L
= 4
Ω)
: P
OUT
MAX (2) = 43 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
= 2
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)
•
•
•
•
•
•
•
Low distortion ratio: THD = 0.015% (typ.)
(V
CC
= 13.2 V, f = 1 kHz, P
OUT
= 5 W, R
L
= 4
Ω)
Low noise: V
NO
= 50 µVrms (typ.)
(V
CC
= 13.2 V, R
g
= 0
Ω,
BW = 20 Hz~20 kHz, R
L
= 4
Ω)
Built-in standby switch function (pin 4)
Built-in muting function (pin 22)
Built-in high-side switch function (pin 25)
Built-in various protection circuits:
Thermal shut down, overvoltage, out to GND, out to V
CC
, out to out short
Operating supply voltage: V
CC (opr)
= 8.0~18 V (R
L
= 4
Ω)
Note 1: Since this device’s pins have a low withstanding voltage, please handle it with care.
Note 2: Install the product correctly. Otherwise, it may result in break down, damage and/or degradation to the
product or equipment.
Note 3: These protection functions are intended to avoid some output short circuits or other abnormal conditions
temporarily. These protect functions do not warrant to prevent the IC from being damaged.
In case of the product would be operated with exceeded guaranteed operating ranges, these protection
features may not operate and some output short circuits may result in the IC being damaged.
Note 4: The protection circuit may operate not correctly in case of the use of large phase-shift type speaker.
Therefore, it should be confirmed that there is no problem on actual evaluation or mass-production board.
Especially, it is necessary to be ware such a behavior when the large phase-shift type 2ohm load, which is
a kind of sub-woofer for example, is connected to this IC, though such kind of speaker use is not
recommended.
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TB2921HQ
Block Diagram
C2
C1
C5
10
Ripple
11
IN1
1
TAB
20
6
Vcc2 Vcc1
9
Out1(+)
C3
+B
RL
8 PW-GND1
7 Out1(-)
C1
IN2
12
13 Pre-GND
IN3
17
5
Out2(+)
RL
2 PW-GND2
3 Out2(-)
15
C1
C6
Out3(+)
RL
AC
16 GND
IN4
14
18 PW-GND3
19
Out3(-)
21 Out4(+)
24 PW-GND4
C1
5V
Play
Mute
4 Stby
R1
22 Mute
C4
RL
23
Out4(-)
.
H-SW/Off-set
High Side SW
25
Note5: Some of the functional blocks, circuits, or constants in the block diagram may be omitted or simplified for
explanatory purpose.
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TB2921HQ
Caution and Application Method
(Description is made only on the single channel.)
1. 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 Power
OFF
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)
0~0.5
2.5~6 V
When changing the time constant of pin 4, check the
pop noise.
Figure 1 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.
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 2
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TB2921HQ
2. 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 3
and Figure 4.)
The pin 22 is designed to operate off 5 V so that the outside pull-up resistor R
1
is determined on the basic
of this value:
ex) When control voltage is changed in to 3.3 V from 5 V.
3.3 V/5 V
×
47 k
=
31 k
Additionally, as the V
CC
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 R
1
is too small value.
To obtain enough operation of the internal low voltage muting, a series resistor, R
1
at pin 22 should be 47
kΩ or more.
20
0
VCC
=
13.2 V
f
=
1kHz
RL
=
4
Ω
VOUT
=
20dBm
ATT – V
MUTE
(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 3
Muting Function
Figure 4
Mute Attenuation
−
V
MUTE
(V)
3. High-Side Switch
Pin 25 of this device is used in concerned with V
CC
as a high-side switch which operates with the standby
pin. Thus, both the power amp IC and the connected external unit (the hideaway unit) can be turned
ON/OFF by using of the standby switch.
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TB2921HQ
4. Off-set detection function
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
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
5. Pop Noise Suppression
Since the AC-GND pin (pin 16) is used as the NF pin for all amps, the ratio between the input
capacitance (C1) and the AC-to-GND capacitance (C6) should be 1:4.
Also, if the power is turned OFF before the C1 and C6 batteries have been completely charged, pop noise
will be generated because of the DC input unbalance.
To counteract the noise, it is recommended that a longer charging time be used for C2 as well as for C1
and C6. Note that the time which audio output takes to start will be longer, since the C2 makes the muting
time (the time from when the power is turned ON to when audio output starts) is fix.
The pop noise which is generated when the muting function is turned ON/OFF will vary according to the
time constant of C4.The greater the capacitance, the lower the pop noise. Note that the time from when the
mute control signal is applied to C4 to when the muting function is turned ON/OFF will be longer.
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