TA8221AHQ / ALQ
TOSHIBA Bipolar Linear Integrated Circuit Silicon Monolithic
TA8221AHQ,TA8221ALQ
30W BTL
×
2Ch Audio Power Amplifier
The thermal resistance
θj−T
of TA8221AHQ, TA8221ALQ
package designed for low thermal resistance, has a high efficiency
of heat radiation.
The temperature rise of chip can be reduced, and the influence
from the degradation of the features due to the temperature rise
at the high output can also be reduced.
This stereo audio power IC, designed for car audio use, has two
built−in channels to reduce the characteristic difference between
L and R channels.
It also contains various kind of protection.
TA8221AHQ
TA8221ALQ
Features
•
•
Low thermal resistance
:
θj−T
= 1.5°C / W (infinite heat sink)
High power
: P
OUT (1)
= 30W (typ.) / channel
(V
CC
= 14.4V, f = 1kHz, THD = 10%, R
L
=2Ω)
P
OUT (2)
= 26W (typ.) / channel
(V
CC
= 13.2V, f = 1kHz, THD = 10%, R
L
= 2Ω)
P
OUT (3)
= 19W (typ.) / channel
(V
CC
= 13.2V, f = 1kHz, THD = 10%, R
L
= 4Ω)
•
•
•
•
•
•
Low distortion ratio: THD = 0.04% (typ.) (V
CC
= 13.2V, f = 1kHz, P
OUT
= 1W, R
L
= 4Ω, G
V
= 50dB)
Low noise: V
NO
= 0.30mV
rms
(typ.) (V
CC
= 13.2V, R
L
= 4Ω, G
V
50dB, R
g
= 0Ω, BW = 20Hz~20kHz)
Built−in stand−by function (with pin(4) set at low, power is turned off.): I
SB
= 100µA (typ.)
Built−in muting function (with pin(1) set at low, power is turned off.)
Built−in various protection circuits
Protection circuits: Thermal shut down, Over voltage, Out→V
CC
short, Out→GND short and Out−Out short.
Operating supply voltage: V
CC (opr)
= 9~18V
Weight
HZIP17−P−2.00 : 9.8g (typ.)
HSIP17−P−2.00 : 9.8g (typ.)
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TA8221AHQ / ALQ
Block Diagram
TA8221AHQ, TA8221ALQ (G
V
= 50dB)
Cautions And Application Method
1. Voltage gain adjustment
(description is made only on the single channel.)
This IC has the amplifier construction as shown Fig.1. The pre−amp (amp 1) is provided to the primary stage,
and the input voltage is amplified by the flat amps, amp 3 and amp 4 of each channel through the phase amp
(amp 2).
Since the input offset is prevented by pre−amp when V
CC
is set to on, this circuit can remarkably reduce the pop
noise.
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TA8221AHQ / ALQ
The total closed loop gain G
V
of this IC can be obtained by expression below when the closed loop voltage gain of
amp 1 is G
V1
.
G V1
=
20
l
og
R1
+
(Rf
+
R2)
(dB)
R f
+
R2
..... (1)
The closed loop voltage gain of power amp, amp 3
and amp 4 is fixed at G
V3
≒G
V4
= 20dB.
Therefore, the total closed circuit voltage gain G
V
is
obtained through BTL connection by the expression
below.
G
V
= G
V1
+ G
V3
+ 6 (dB) ............... (2)
For example, when Rf = 0Ω, G
V
is obtained by the
expressions (1) and (2) as shown below.
G
V
≒24
+ 20 + 6 = 50dB
The voltage gain is reduced when R
f
is increased. (Fig.2)
With the voltage gain reduced, since (1) the oscillation
stability is reduced, and (2) the pop noise changes when
V
CC
is set to on, refer to the items 3 and 4.
2. Stand−by SW function
By means of controlling pin(4) (stand−by terminal) to high
and low, the power suply can be set to on and off.
The threshold voltage of pin(4) is set at 2.1V (3V
BE
.),
and the power supply current is about 100µA (typ.) at the
stand−by state.
Control voltage of pin(4): V
(SB)
Stand
−
by
On
Off
Power
Off
On
V
(SB)
(V)
0~2
3~V
CC
Advantage of stand−by SW
(1) Since V
CC
can directly be controlled to on / off by the microcomputer, the switching relay can be omitted.
(2) Since the control current is microscopic, the switching relay of small current capacity is satisfactory for
switching.
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TA8221AHQ / ALQ
3. Preventive measure against oscillation
For preventing the oscillation, it is advisable to use C4, the condenser of polyester film having small
characteristic fluctuation of the temperature and the frequency.
The condenser (C6) between input and GND is effective for preventng oscillation which is generated with a
feedback signal from an output stage.
The resistance R to be series applied to C4 is effective for phase correction of high frequency, and improves the
oscillation allowance.
(1) Voltage gain to be used (G
V
setting)
(2) Capacity value of condenser
(3) Kind of condenser
(4) Layout of printed board
In case of its use with the voltage gain G
V
reduced or with the feedback amount increased, care must be taken
because the phase−inversion is caused by the high frequency resulting in making the oscillation liable generated.
4. Adjustment of output offset (when the power supply turn on)
As this IC is contructed with DC circuit on the primary stage, it is necessary to lower a input offset or output
offset by agreement with the each leading edge time constant of the input voltage in the primary stage and NF
terminal voltage.
Concretely, monitor the output DC voltage and vary the capacity value in input condenser and NF condenser (see
Fig.4)
(reference) In case of setting the condition (G
V
= 40dB) with R
f
= 470Ω.
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TA8221AHQ / ALQ
5. Muting function
Through setting pin(1) (mute terminal) at about 1V or less, muting
becomes possible.
The interval circuit of IC is shown in Fig.5.
When pin(1) is set to low, Q1 and Q2 are turned to on, the charge
of the ripple condenser is discharged and the bias is cut. The mute
amount of 60dB or over can be obtained.
Since this muting function rapidly discharge the charge of the ripple
filter capacitor of pin(8), the pop noise is generated by the DC
fluctuation of the bias section.
Therefore, this muting function is not appropriate to the audio muting but it
is effective in muting at V
CC
→on.
6. Rapid ripple discharging circuit at the time of V
CC
off
This circuit is effective in such a mode where the V
CC
and the stand−by terminals become high / low
simultaneously ; for instance, for a pop noise produced when the power is turned on / off repeatedly by operating
the ignition key.
If V
CC
is off, V
CC
≒7V
is detected internally on IC and
(1) The power stage bias circuit is cut, and
(2) Pin(8) : Ripple capacitor is rapidly discharged by turning Q3 on and then Q1 and Q2 on.
(Precaution 1)
When the stand−by terminal was put to the low level after the ripple rapid
discharging circuit was operated (V
CC
≒7V)
at the time when V
CC
was turned
off, a pop noise may be generated. Therefore, V
CC
which makes the stand−by
terminal low shall be set at 8V or above so that (1) the stand−by terminal is
put at the low level and (2) the ripple rapid discharging circuit is turned on
when V
CC
is turned off (in order of (1) and (2)).
An example of application is shown in (Fig.7).
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2006-04-28
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