TPA2005D1 Datasheet, PDF (19/22 Pages) Texas Instruments – 1.1 W MONO FILTER FREE CLASS D AUDIO POWER AMPLIFIER

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TPA2005D1
SLOS369B – JULY 2002 – REVISED DECEMBER 2002
When to Use an Output Filter
Design the TPA2005D1 without an output filter if the traces from amplifier to speaker are short. The TPA2005D1
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 very 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.
OUTP
OUTN
Ferrite
Chip Bead
Ferrite
Chip Bead
1 nF
1 nF
Figure 35. Typical Ferrite Chip Bead Filter (Chip bead example: NEC/Tokin: N2012ZPS121)
OUTP
OUTN
33 µH
33 µH
1 µF
1 µF
Figure 36. Typical LC Output Filter, Cutoff Frequency of 27 kHz
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