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Philips Semiconductors
2
8 W stereo BTL audio output amplifier
with DC volume control
2.0
handbook, halfpage
V in
(V)
1.6
1.2
0.8
0.4
0
0
4
THD = 1 %.
Fig.11 Input signal handling.
APPLICATION INFORMATION
The application diagram is illustrated in Fig.13.
Test conditions
T
= 25 C unless otherwise specified; V
amb
V
= 1.4 V; f
= 1 kHz; R
DC
i
The quiescent current has been measured without load
impedance.
The output power as a function of the supply voltage has
been measured at THD = 10%. The maximum output
power is limited by the maximum power dissipation and the
maximum available output current.
The maximum input signal voltage is measured at
THD = 1% at the output with a voltage gain of 0 dB.
To avoid instabilities and too high a distortion, the input
ground and power ground must be separated as far as
possible and connected as close as possible to the IC.
The DC volume control can be applied in several ways.
Two possible circuits are shown below the main
application diagram. The circuits at the control pin will
influence the switch-on and switch-off behaviour and the
maximum voltage gain.
1998 Apr 07
MBG665
8
12
16
20
V P (V)
= 12 V;
P
= 16 .
L
30
handbook, halfpage
I VC
( A)
20
10
0
10
20
30
0
0.4
Fig.12 Volume control current as a function of
volume control voltage.
For single-end applications the output peak current must
not exceed 100 mA. At higher output currents the
short-circuit protection (MCL) will be active.
Thermal considerations:
At high junction temperatures (>125 C) the voltage gain
will decrease when it is higher than 0 dB. This results in a
decrease of the output voltage and an increase of the
distortion level. Thus for an optimal performance of the IC
the heatsink has to be designed properly.
Calculation example for application: V
stereo sine wave; worst case sine wave power dissipation
is 12 W.
For T
= 40 C the thermal resistance from junction
amb(max)
to ambient
R
=
---------------------------- -
th j-a
The thermal resistance of the heatsink becomes:
R
= R
(R
th h-a
th j-a
th j-c
R
= 7.1
(4 + 0.1) = 3 K/W.
th h-a
It should be noted that for 'music power' the power
dissipation will be approximately half of the sine wave
dissipation. Thus a smaller heatsink can be used.
9
Product specification
TDA7057AQ
MBG666
0.8
1.2
1.6
V VC (V)
= 15 V; R
P
125 40
–
=
7.1 K/W
12
+ R
);
th c-h
2.0
= 8 ,
L
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