Datasheet

When to Use an Output Filter
1nF
Ferrite
ChipBead
V
O-
Ferrite
ChipBead
1nF
V
O+
0.1 Fm
33 Hm
33 Hm
V
O-
V
O+
0.1 Fm
0.47 Fm
TPA2006D1
SLOS498A – SEPTEMBER 2006 – REVISED JULY 2008 ................................................................................................................................................. www.ti.com
Design the TPA2006D1 without an output filter if the traces from amplifier to speaker are short. The TPA2006D1
passed FCC and CE radiated emissions with no shielding with speaker trace wires 100 mm long or less.
Wireless handsets and PDAs are great applications for class-D without a filter.
A ferrite bead filter can often be used if the design is failing radiated emissions without an LC filter, and the
frequency sensitive circuit is greater than 1 MHz. This is good for circuits that just have to pass FCC and CE
because FCC and CE only test radiated emissions greater than 30 MHz. If choosing a ferrite bead, choose one
with high impedance at high frequencies, but low impedance at low frequencies.
Use an LC output filter if there are low frequency ( < 1 MHz) EMI sensitive circuits and/or there are long leads
from amplifier to speaker.
Figure 35 and Figure 36 show typical ferrite bead and LC output filters.
Figure 35. Typical Ferrite Chip Bead Filter (Chip bead example: NEC/Tokin: N2012ZPS121)
Figure 36. Typical LC Output Filter, Cutoff Frequency of 27 kHz
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Product Folder Link(s): TPA2006D1