TDA7350A datasheet(16/23 Pages) STMICROELECTRONICS

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TDA7350A

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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.

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).

5.2 TURN-ON

Fig. 42 shows the output waveform (before and af-

ter the "A" weighting filter) compared to the value

of Csvr.

Better pop-on performance is obtained with higher

Csvr values (the recommended range is from 22

µF

to 220

µF).

The turn-on delay (during which the amplifier is in

mute condition) is a function essentially of : Cout,

Csvr. Being:

≈ 120 · Cout

≈ 1200 · Csvr

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.

Figure 42.

a) Csvr = 22 µF

b) Csvr = 47 µF

c) Csvr = 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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