TA8220HQ
TOSHIBA Bipolar Linear Integrated Circuit Silicon Monolithic
TA8220HQ
30W BTL × 2ch Audio Power Amplifier
The thermal resistance
θj−T
of TA8220HQ package designed for
low thermal resistance, has 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 output short detection circuit,
output clip detection and various kind of protection.
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)
Weight: 9.8g (typ.)
•
•
•
•
•
•
•
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 (4)pin set at low, power is turned off.): I
SB
= 1µA (typ.)
Built−in output short detection circuit ((9)pin: Open collector)
Built−in output clip detection circuit ((1)pin: Open collector)
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
= 9~18V
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TA8220HQ
Block Diagram
TA8220HQ (G
V
= 50dB)
Caution And Application Method
1. Voltage gain adjustment
(description is made only on the single channel.)
This IC has the amplifier constructions as shown Fig.1. The pre−amp (amp1) is provided to the primary stage,
and the input voltage is amplified by the flat amps, amp3 and amp4 of each channel through the phase amp
(amp2).
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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TA8220HQ
The total closed loop gain G
V
of this IC can be obtained by expression below when the closed loop voltage gain of
amp1 is G
V1
.
R
+
(Rf
+
R2 )
G V1
=
20
l
og 1
(dB)
LLL
(1)
R f
+
R2
The closed loop voltage gain of power amp, amp3 and amp4 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 R
f
= 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 (4)pin (stand−by terminal) to
high and low, the power supply can be set to on and off.
The threshold voltage of (4)pin is set at 2.1V (3V
BE
), and
the power supply current is about 1µA (typ.) at the
stand−by state.
Control voltage of (4)pin: V
(SB)
Stand
−
By
On
Off
Power
Off
On
V
(SB)
(V)
0~2
3~V
CC
<Adjustage 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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TA8220HQ
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 preventing oscillation which is generated with a
feedback signal from a 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 constructed with DC circuit on the pre−amp 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 pre−amp 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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TA8220HQ
5. Output clip detection function (pin(1))
The output clip detection terminal of pin(1) has the open collector output structure on clip as shown in Fig.5. In
case that the output waveform is clipping, the clip detection circuit is operated and NPN Tr. is turned on.
It is possible to improve the tone quality with the current of flowing into pin(1) and with controlling the volume,
tone½control circuit through L.P.F smoothing circuit as shown in Fig.5.
In case of being unused this function, use this IC as open connection on pin(1).
(Application)
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