Datasheet

1nF
Ferrite
ChipBead
OUTP
OUTN
Ferrite
ChipBead
1nF
2.2 mF
15 Hm
15 mH
OUTP
OUTN
L1
L2
C2
C3
2.2 mF
1 mF
1 mF
33 Hm
33 mH
OUTP
OUTN
L1
L2
C2
C3
TPA3111D1
SLOS618E –AUGUST 2009–REVISED AUGUST 2012 www.ti.com
When to Use an Output Filter for EMI Suppression
The TPA3111D1 has been tested with a simple ferrite bead filter for a variety of applications including long
speaker wires up to 125 cm and high power. The TPA3111D1 EVM passes FCC Class B specifications under
these conditions using twisted speaker wires. The size and type of ferrite bead can be selected to meet
applicaton requirements. Also, the filter capacitor can be increased if necessary with some impact on efficiency.
There may be a few circuit instances where it is necessary to add a complete LC reconstruction filter. These
circumstances might occur if there are nearby circuits which are very sensitive to noise. In these cases a classic
second order Butterworth filter similar to those shown in the figures below can be used.
Figure 19. Typical LC Output Filter, Cutoff Frequency of 27 kHz, Speaker Impedance = 8 Ω
Figure 20. Typical LC Output Filter, Cutoff Frequency of 27 kHz, Speaker Impedance = 4 Ω
Figure 21. Typical Ferrite Chip Bead Filter (Chip Bead Example: Steward HI0805R800R-10)
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