TA8205AHQ/ALQ
TOSHIBA Bipolar Linear Integrated Circuit Silicon Monolithic
TA8205AHQ,TA8205ALQ
18W BTL
×
2CH Audio Power Amplifier
TA8205AHQ
The thermal resistance
θj−T
of TA8205AHQ, TA8205ALQ
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.
In addition, the functions of stand−by and muting, and a variety
of protection circuits are involved.
TA8205ALQ
Features
•
•
Low thermal resistance
:
θj−T
= 1.5°C / W (infinite heat sink)
High power
: P
OUT (1)
= 18W (typ.) / channel
(V
CC
= 14.4V, f = 1kHz, THD = 10%, R
L
= 4Ω)
P
OUT (2)
= 15W (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
= 1µA (typ.)
Built−in muting function (with pin(1) set at low, power is turned off.) : V
(mute)
= 1V (typ.)
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
Weight
HZIP17−P−2.00 : 9.8g (typ.)
HSIP17−P−2.00 : 9.8g (typ.)
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TA8205AHQ/ALQ
Block Diagram
TA8205AHQ, TA8205ALQ (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 in 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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2006-04-28
TA8205AHQ/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
.
GV1
=
20
l
og
R1
+
(Rf
+
R2)
(dB)
Rf
+
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, GV 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.
Fig.2
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 about 3V (typ.),
and the power supply current is about 1µA (typ.) at the
stand−by state.
Pin(4) control voltage : V
(SB)
Stand
−
by
On
Off
Power
Off
On
V
(SB)
(V)
0~2
3~V
CC
Fig.3 With pin(4) set to high, power is turened on.
Advantage of stand−by SW
(1) Since V
CC
can directly be controlled to on / off by the microcomuter, 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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TA8205AHQ/ALQ
3. 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 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 condernse
(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 generated.
4. Input offset prevention circuit at V
CC
→on
Having pre−amp (amp 1) mounted on the primary stage, this IC contains the circuit for making the amp 1 input
voltage and the NF terminal voltage equipotential.
Therefore, the offset voltage produced at the input stage is suppressed to prevent the pop noise at V
CC
→on.
The
capacity values of the input and NF condense (C
1
and C
2
) shall be set according to the gain to be used.
(reference) (A) At G
V
= 50dB (R
f
= 0Ω)
C
1
= 4.7µF, C
2
= 47µF
(B) At G
V
= 40dB (R
f
= 470Ω)
C
1
= 3.3µF, C
2
= 33µF
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TA8205AHQ/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.4.
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 mute function rapidly discharges 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. External parts list and description
Symbol
Recom
−
mended
Value
4.7µF
Influence
Feature
Smaller Than
Recommended Value
Related to pop noise at V
CC
→on.
Related to pop noise at V
CC
→on.
determination of low cut
−
off frequency.
C
2
47µF
Feedback
condenser
C
2
=
1
2
π
・
fL R f
・
Time constant is large
at V
CC
→on
or off.
Oscillation allowance
improved.
Refer to item 3.
Larger Than
Recommended Value
Remarks
Related to gain.
Refer to item 4.
C
1
DC blocking
C
3
C
4
220µF
0.12µF
Ripple
reduction
Oscillation
prevention
Repple
filter
Time constant is small
at V
CC
→on
or off.
Made liable to
oscillate.
C
5
1000µF
For filtering power supply hum and ripple.
Large at using AC rectified power supply.
Small at using DC power supply.
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2006-04-28
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