Applications information
TDA7498L
5.6
Output low-pass filter
To avoid EMI problems, it may be necessary to use a low-pass filter before the speaker. The
cutoff frequency should be larger than 22 kHz and much lower than the output switching
frequency. It is necessary to choose the L and C component values depending on the
loudspeaker impedance. Some typical values, which give a cutoff frequency of 27 kHz, are
shown in Figure 25 and Figure 26 below.
Figure 25. Typical LC filter for a 8-Ω speaker
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ꢀꢀU(
ꢃOHM
ꢀꢀꢁN&
ꢂꢂꢁP&
ꢀꢀꢁN&
ꢅꢄꢁN&
ꢃOHM
ꢀꢀOHM
ꢀꢀꢁN&
ꢀꢀꢁN&
ꢀꢀU(
ꢃOHM
07-?.
Figure 26. Typical LC filter for a 6-Ω speaker
07-?0
ꢀꢀU(
ꢃOHM
ꢀꢀꢁN&
ꢂꢂꢁP&
ꢀꢀꢁN&
ꢆꢃꢁN&
ꢆOHM
ꢀꢀOHM
ꢀꢀꢁN&
ꢀꢀꢁN&
ꢀꢀU(
ꢃOHM
07-?.
22/27
Doc ID 16504 Rev 3
STMICROELECTRONICS [ ST ]
