TDA7350A_05 Datasheet, PDF (16/23 Pages) STMicroelectronics – 22W BRIDGE-STEREO AMPLIFIER FOR CAR RADIO

TDA7350A
5 Application Hints
This section explains briefly how to get the best
from the TDA7350A and presents some applica-
tion circuits with suggestions for the value of the
components.These values can change depending
on the characteristics that the designer of the car
radio wants to obtain,or other parts of the car radio
that are connected to the audio block.
To optimize the performance of the audio part it is
useful (or indispensable) to analyze also the parts
outside this block that can have an interconnection
with the amplifier.
This method can provide components and system
cost saving.
Figure 42.
a) C_svr = 22 µF
5.1 Reducing Turn On-Off Pop
The TDA7350A has been designed in a way that
the turn on(off) transients are controlled through
the charge(discharge) of the Csvr capacitor.
As a result of it, the turn on(off) transient spectrum
contents is limited only to the subsonic range.The
following section gives some brief notes to get the
best from this design feature(it will refer mainly to
the stereo application which appears to be in most
cases the more critical from the pop viewpoint.The
bridge connection in fact,due to the common mode
waveform at the outputs,does not give pop effect).
b) C_svr = 47 µF
5.2 TURN-ON
Fig. 42 shows the output waveform (before and af-
ter the "A" weighting filter) compared to the value
of C_svr.
Better pop-on performance is obtained with higher
C_svr values (the recommended range is from 22µF
to 220µF).
The turn-on delay (during which the amplifier is in
mute condition) is a function essentially of : C_out,
C_svr. Being:
T1 ≈ 120 · C_out
T2 ≈ 1200 · C_svr
The turn-on delay is given by:
T1+T2 STEREO
T2 BRIDGE
The best performance is obtained by driving the st-
by pin with a ramp having a slope slower than 2V/
ms.
c) C_svr = 100 µF
5.3 TURN-OFF
A turn-off pop can occur if the st-by pin goes low
with a short time constant (this can occur if other
car radio sections, preamplifiers,radio.. are sup-
plied through the same st-by switch).
This pop is due to the fast switch-off of the internal
current generator of the amplifier.
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