TS4961T datasheet(40/49 Pages) STMICROELECTRONICS

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Application component information

TS4961T

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4.8

Output filter considerations

The TS4961T is designed to operate without an output filter. However, due to very sharp

transients on the TS4961T output, EMI radiated emissions may cause some standard

compliance issues.

These EMI standard compliance issues can appear if the distance between the TS4961T

outputs and loudspeaker terminal are long (typically more than 50 mm, or 100 mm in both

directions, to the speaker terminals). Since the PCB layout and internal equipment device

are different for each configuration, it is difficult to provide a one-size-fits-all solution.

However, to decrease the probability of EMI issues, there are several simple rules to follow.

●

Reduce, as much as possible, the distance between the TS4961T output pins and the

speaker terminals.

●

Use ground planes for shielding sensitive wires.

●

Place, as close as possible to the TS4961T and in series with each output, a ferrite

bead with a rated current of 2.5 A minimum, and impedance greater than 50

Ω at

frequencies above 30 MHz. If, after testing, these ferrite beads are not necessary,

replace them by a short circuit.

●

Allow enough footprint to place, if necessary, a capacitor to short perturbations to

ground as shown in Figure 78.

Figure 78.

Output filter for shorting pertubations to ground

In the case where the distance between the TS4961T outputs and speaker terminals is high,

it is possible to have low frequency EMI issues due to the fact that the typical operating

frequency is 250 kHz.

In this configuration, it is recommended to use an output filter. It should be placed as close

as possible to the TS4961T.

Ferrite chip bead

about 100pF

Gnd

From TS4961T output

To speaker

Obsolete

Product(s)

- Obsolete

Product(s)

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