TA8248K
2002-04-05
1
TOSHIBA Bipolar Linear Integrated Circuit Silicon Monolithic
TA8248K
Low Frequency Power Amplifier
TA8248K is an audio power IC with built-in two channels
developed for portable radio cassette tape recorder with power
ON/OFF switch.
Because of the parts reduction and SIP (Single Inline Package),
space merit is remarkable.
Thermal shut down protection circuit is built in.
Features
High Power
:
P
out (1)
= 2.5 W (typ.)
(V
CC
= 9 V, R
L
= 4, f = 1 kHz, THD = 10%)
:
P
out (2)
= 4.6 W (typ.)
(V
CC
= 12 V, R
L
= 4, f = 1 kHz, THD = 10%)
Low Popping Noise at Power ON
Small Quiescent Current
:
I
CCQ
= 21 mA (typ.) (V
CC
= 15 V, V
in
= 0)
Soft Clip
Built-in Thermal Shut Down Protection Circuit
Best for Supply Voltage 9 V, 12 V
Operation Supply Voltage Range : V
CC (opr)
= 6~15 V (Ta = 25C)
Weight: 3.9 g (typ.)
TA8248K
2002-04-05
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Block Diagram
TA8248K
2002-04-05
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Application Information And Application Method
1. Adjustment of voltage gain
The voltage gain G
v
is obtained as follows by R1, R2 and R
f
in Fig.1.
R1
+
Rf
R2
+
R1
+
Rf
og
20
=
Gv
l
When
R
f
= 0 , G
v
= 56.5dB (typ.)
When
R
f
= 120 , G
v
= 45dB (typ.)
Figure 1
By increasing R
f
, reduction of G
v
is possible. However, since the feedback increase is liable to produce
oscillation, it is recommended to use this at 40dB or over.
2. Thermal shut-down circuit
The thermal shut-down circuit is built in for the purpose of preventing the destruction of IC due to the
abnormal temperature rise when the heat radiation is insufficient.
The operation temperature is set at radiation Fin temperature 175C (typ.). At this temperature or over the
bias is interrupted to prevent the destruction of IC.
3. Input
stage
The input circuit of this IC is as shown in Fig.2.
PNP Tr : Q1 is provided in the input circuit so as to make its usage possible without the input coupling
capacitor.
However, at pin11 and 12, max 60 mV offset voltage is produced.
Application after checking volume slide noise is recommended.
For cutting the volume slide noise, insert the input capacitor : C
IN
in series to interrupt the DC component.
Figure 2
TA8248K
2002-04-05
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4. Oscillation
preventive
measures
For oscillation preventive capacitor C6 and C7 between the output terminal and GND, it is recommended
to use polyester film capacitor having good characteristics for temperature and for high frequency.
Since the characteristics of the capacitor is liable to be influenced by the temperature, use this capacitor
after the temperature test to check the oscillation allowance.
In addition, as the position of the electrolytic capacitor has a remarkable influence on the oscillation,
connect C10 to V
CC
at the nearest possible position from power GND.
At using this application with the voltage gain reduced, oscillation is liable to be produced. Apply the
capacitor after checking enough for its capacity, type and mounting position.
Note 1: As the oscillation allowance varies according to the printed pattern layout, the standard printed board
of TOSHIBA is recommended to be referred to design it.
5. Power
ON/OFF
switch
There is power ON/OFF switch at pin8. However, output power is changed by pin8 supply voltage when
pin8 supply voltage is not same pin4 supply voltage, after referring to attached date, select pin8 supply
voltage.
6. Input
voltage
When the excessive signal is input, turning-up is produced in the clip waveform.
The turning-up point is V
in
= 300 mVrms (typ.) : V
CC
= 9 V, R
L
= 4 , f = 1 kHz : Enough care must be
taken for this phenomenon.
Maximum Ratings
(Ta = 25C)
Characteristics Symbol
Rating
Unit
Supply voltage
V
CC
20 V
Output current (peak/CH)
I
O (peak)
2.5 A
Power dissipation
P
D
(Note 2)
15.0
W
Operating temperature
T
opr
-20~75 C
Storage temperature
T
stg
-55~150 C
Note 2: Derated above Ta = 25C in the proportion of 120 mW/C.
TA8248K
2002-04-05
5
Electrical Characteristics
(unless otherwise specified, V
CC
= 9 V, R
L
= 4 , R
g
= 600 , f = 1 kHz, Ta = 25C, R
f
= 120 )
Characteristics Symbol
Test
Circuit
Test Condition
Min
Typ.
Max
Unit
Quiescent current
I
CCQ
V
in
= 0
21 45 mA
P
out (1)
THD = 10%
2.0
2.5
Output power
P
out (2)
THD = 10%, V
CC
= 12 V
4.6
W
Total harmonic distortion
THD
P
out
= 0.4 W/ch
0.2 1.0 %
G
v (1)
R
f
= 120 ,
V
out
= 0.775 Vrms (0dBm)
43 45 47
Voltage gain
G
v (2)
R
f
= 0,
V
out
= 0.775 Vrms (0dBm)
56.5
dB
Input resistance
R
IN
30
k
Output noise voltage
V
no
R
g
= 10 k,
BW = 20 Hz~20 kHz
0.3 1.0
mVrms
Ripple rejection ratio
R.R.
R
g
= 600 , f
ripple
= 100 kHz
-52
dB
Cross talk
C.T.
R
g
= 600 , amp1
2,
V
out
= 0.775 Vrms (0dBm)
-50
dB
Input offset voltage
V
11
, V
12
30 60 mV
Stand-by current
I
OFF
SW1
OFF
1 A
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