TA8225HQ/LQ
TOSHIBA Bipolar Linear Integrated Circuit Silicon Monolithic
TA8225HQ,TA8225LQ
45W BTL Audio Amplifier
The TA8225HQ, TA8225LQ is BTL audio power amplifier for
consumer application.
It is designed for high power, low distortion and low noise.
It contains various kind of protectors and the function of
stand−by SW.
In addition, the functions of output short or over voltage
detection and junction temperature are involved.
TA8225HQ
Features
•
High power
: P
OUT (1)
= 45W (typ.)
(V
CC
= 14.4V, f = 1kHz, THD = 10%, R
L
= 2Ω)
: P
OUT (2)
= 40W (typ.)
(V
CC
= 13.2V, f = 1kHz, THD = 10%, R
L
= 2Ω)
: P
OUT (3)
= 24W (typ.)
(V
CC
= 13.2V, f = 1kHz, THD = 10%, R
L
= 4Ω)
Low thermal resistance
:
θ
j−c
= 1.5°C / W (infinite heat sink)
Excellent output power band width
: P
OUT (4)
= 18W (typ.)
(V
CC
= 13.2V, f = 50Hz~20kHz, THD = 1%, R
L
= 4Ω)
Low distortion ratio
: THD = 0.015% (typ.)
(V
CC
= 13.2V, f = 1kHz, P
OUT
= 4W, R
L
= 4Ω)
TA8225LQ
•
•
Weight
HZIP17−P−2.00: 9.8g (typ.)
HSIP17−P−2.00: 9.8g (typ.)
•
•
•
•
•
Built−in stand−by function (with pin(1) set at high, power is turned on)
Built−in output short or over voltage detection circuit, output to V
CC
and output to GND short.
(Pin(8): Open collector)
Built−in junction temperature detection circuit. (Pin(2): Open collector)
Built−in various protection circuits
•
Thermal shut down, Over voltage
•
Output to GND short
•
Output to V
CC
short
•
Output to Output short
•
Operating supply voltage: V
CC (opr)
= 9~18V
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TA8225HQ/LQ
Block Diagram
TA8225HQ/LQ (G
V
=
40dB)
Caution For Use And Method Of Application
1. Voltage gain adjustment
Voltage gain G
V
of this IC is decided by the external feedback resistors R
f1
and R
f2
.
Gain fluctuation by temperature can be made smaller than they are housed in IC.
Voltage gain G
V
is decided by the following expression:
If R
0
= 20kΩ≫R
f1
> R
f2
If R
0
= 20kΩ > R
f1
> R
f2
G
V
≒
20
ℓ
og
G
V
≒
20
ℓ
og
R f1
+
R f2
+
6 (dB)
R f2
(R0 // R f1)
+
R f2
+
6 (dB)
R f2
If R
f1
and R
f2
are made small, the following problems may be caused:
(1) When output short is released, output DC voltage is not restored.
(2) Fluctuation of output DC voltage by current I in (Fig.1).
If voltage gain is made small excessively, oscillation may be taken place and therefore, this IC shall be used at
G
V
= 34dB or above.
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TA8225HQ/LQ
2. Preventive measure against oscillation
For preventing the oscillation, it is advisable to use C
4
, the condenser of polyester film having small
characteristic fluctuation of the temperature and the frequency.
The condenser (C
6
) between input and GND is effective for preventing oscillacion which is generated with
feedback signal from an output stage.
The resistance R to be series applied to C
4
is effective for phase correction of high frequency, and improves the
oscillation allowance.
Since the oscillation allowance is varied according to the causes described below, perform the temperature test
to check 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.
3. Pop noise
A pop noise generated when the power source is turned on
depends on rise times of the in−phase side output ((11)pin) and
the negative−phase side output ((16)pin), that is, output offset
voltage.
The following two points may be pointed out as causes for
generation the output offset voltage:
(1) In−phase and negative−phase NF capacitor charging times
(2) Input offset voltage
Especially, the factor (2) relates to the pop noise level.
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2006-04-28
TA8225HQ/LQ
(1) In−phase and negative phase NF capacitor charging time
In (Fig.2), when the power source is turned on, Q
1
and Q
2
are turned on, and NF capacitors are charged in
the route of V
CC
→Q
2
→R→boot→C
BS
→out→R
0
→C
NF
. For instance, if the capacity of an in−phase capacitor
is not properly paired with that a negative−phase capacitor, output offset voltage = pop noise is produced
because a charging time of NF capacitor differs between the in−phase and negative−phase outputs.
Therefore, to suppress the pop noise it is necessary to properly pair the in−phase and negative−phase NF
capacitors. Output and NF DC voltage waveforms by the pairing of NF capacitors: C
NF
are shown in (Fig.3)
and (Fig.4).
Further, voltage waveforms are shown when the power source was turned on, under the following conditions:
V
CC
= 13.2V, R
L
= 4Ω, Ta = 25°C, and input shot−circuit.
Output DC voltage V
OUT
: (2V / div, 200ms / div)
NF DC voltage V
NF
: (1V / div, 200ms / div)
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TA8225HQ/LQ
(2) Input offset voltage
Input offset voltage is increased by as many times as a gain and appears as output offset voltage.
Input offset voltage is affected by an external resistor in addition to properness of pair of capacitor in IC.
An example of a general application circuit is shown in (Fig.5). In this case, input to the differential amplifier
composing the buffer amplifier is decided to be 30kΩ + 1.1kΩ = 31.1kΩ at the in (+) side and 1.1k at the in (−)
side. Therefore a rising difference of about 30 times between the in (+) side and the in (−) side.
So, to fit input offset voltages, it is possible to suppress the input offset voltage by adjusting it to 31.1kΩ both
at the in (+) and in (−) sides according to the application example shown in (Fig.6). As input coupling
capacitors are used in actual set, the circuit shown in (Fig.7) is considered. In this case, it is necessary to
take the utmost care of proper pair of C
IN
(+) and C
IN
(−).
Pop noise level affected by input offset voltage shall be checked on an actually mounted set.
4. Junction temperature detecting pin(2)
Using temperature characteristic of a band gap circuit and in proportion to junction temperature, pin(2) DC
voltage: V
2
rises at about ±10mV / °C temperature characteristic. So, the relation between V
2
at T
j
= 25°C and
V
2
χ
at T
j
=χ°C is decided by the following expression:
V
χ −
V2 (25
°
C)
Tj (
χ°
C)
=
2
+
25(
°
C)
10mV /
°
C
In deciding a heat sink suze, a junction temperature can be
easily made clear by measuring voltage at this pin while a
backside temperature of IC was so far measured using a
thermocouple type thermometer.
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2006-04-28
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