Datasheet

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WHEN TO USE AN OUTPUT FILTER
1 nF
Ferrite
Chip Bead
V
O−
V
O
+
Ferrite
Chip Bead
1 nF
TPA2032D1
TPA2033D1
TPA2034D1
SLOS476 – JUNE 2006
Design the TPA2032D1 without an output filter if the traces from the amplifier to the speaker are short. Wireless
handsets and PDAs are great applications for this class-D amplifier to be used without an output filter.
The TPA2032D1 passed FCC- and CE-radiated emissions testing with no shielding with speaker trace wires 100
mm long or less. For longer speaker trace wires, a ferrite bead can often be used in the design if failing radiated
emissions testing without an LC filter; and, the frequency-sensitive circuit is greater than 1 MHz. If choosing a
ferrite bead, choose one with high impedance at high frequencies, but very low impedance at low frequencies.
The selection must also take into account the currents flowing through the ferrite bead. Ferrites can begin to
loose effectiveness at much lower than rated current values. Please see the EVM User's Guide for components
used successfully by TI.
Figure 40 shows a typical ferrite-bead output filter.
Figure 40. Typical Ferrite Chip Bead Filter
15
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