1nF

Ferrite

ChipBead

OUTP

OUTN

Ferrite

ChipBead

1nF

2.2 mF

15

H

m

15 mH

OUTP

OUTN

L1

L2

C2

C3

2.2 mF

1 mF

1 mF

33

H

m

33 mH

OUTP

OUTN

L1

L2

C2

C3

TPA3110D2

SLOS528E – JULY 2009 – REVISED NOVEMBER 2015

www.ti.com

Feature Description (continued)

9.3.1.3 When to Use an Output Filter for EMI Suppression

The TPA3110D2 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 TPA3110D2 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

application 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 sensitive to noise. In these cases a classic

second order Butterworth filter similar to those shown in the figures below can be used.

Some systems have little power supply decoupling from the AC line but are also subject to line conducted

interference (LCI) regulations. These include systems powered by "wall warts" and "power bricks." In these

cases, it LC reconstruction filters can be the lowest cost means to pass LCI tests. Common mode chokes using

low frequency ferrite material can also be effective at preventing line conducted interference.

Figure 37. Typical LC Output Filter, Cutoff Frequency of 27 Khz, Speaker Impedance = 8

Ω

Figure 38. Typical Lc Output Filter, Cutoff Frequency Of 27 Khz, Speaker Impedance = 4

Ω

Figure 39. Typical Ferrite Chip Bead Filter (Chip Bead Example)

9.3.2 Gain Setting Via GAIN0 And GAIN1 Inputs

The gain of the TPA3110D2 is set by two input terminals, GAIN0 and GAIN1. The voltage slew rate of these gain

terminals, along with terminals 1 and 14, must be restricted to no more than 10V/ms. For higher slew rates, use

a 100k

Ω resistor in series with the terminals.

16

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