TDA749313TR Datasheet, PDF (16/30 Pages) STMicroelectronics – 3-watt 3-watt dual BTL class-D audio amplifier

Applications information
TDA7493
5.6
Output low-pass filter
To avoid EMI problems, a low-pass filter can be inserted before the speaker. The cut-off
frequency of the filter should be higher than 22 kHz and much lower than the switching
frequency.
The component values of the filter vary according to the speaker impedance.
A typical LC output filter for a speaker impedance of 8 Ω and with a cut-off frequency of
27 kHz is shown in Figure 9.
Figure 9. Typical LC filter for 8 Ω speaker
OUTP
OUTN
33 µH
0.10 µF
330 pF
20 Ω
0.47 µF
8Ω
33 µH
0.10 µF
A similar filter for a speaker impedance of 4 Ω and also with a cut-off frequency of 27 kHz is
shown in Figure 10:
Figure 10. Typical LC filter for 4 Ω speaker
OUTP
OUTN
15 µH
0.22 µF
330 pF
20 Ω
0.47 µF
4Ω
15 µH
0.22 µF
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Doc ID 14570 Rev 6