TS4962M datasheet(32/41 Pages) STMICROELECTRONICS

32 / 41 page

Application information

TS4962M

32/41

We have the following equations:

In general, for mixed situations (single-ended and differential inputs), it is best to use the

same rule, that is, to equalize impedance on both TS4962M inputs.

5.10

Output filter considerations

The TS4962M is designed to operate without an output filter. However, due to very sharp

transients on the TS4962M output, EMI radiated emissions may cause some standard

compliance issues.

These EMI standard compliance issues can appear if the distance between the TS4962M

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

directions, to the speaker terminals). As 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 TS4962M output pins and the

speaker terminals.

●

Use ground planes for “shielding” sensitive wires.

●

Place, as close as possible to the TS4962M and in series with each output, a ferrite

bead with a rated current at minimum 2A and impedance greater than 50

Ω at

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

replace them by a short-circuit. Murata BLM18EG221SN1 or BLM18EG121SN1 are

possible examples of devices you can use.

●

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

ground (see the schematics in Figure 63).

Figure 63.

Method for shorting pertubations to ground

Out

–

300

in1

-------------

×… V

300

ink

-------------

(V)

inj

π R

inj

CLj

-------------------------------------------------------

(F)

inj

----------

∑

-------------------

Ferrite chip bead

about 100pF

Gnd

From TS4962 output

To speaker

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