TS4962_10 Datasheet, PDF (34/44 Pages) STMicroelectronics – 2.8 W filter-free mono class D audio power amplifier

Application information
TS4962
We have the following equations.
Out+
– Out-
=
Ve1 ×
--3----0---0---
Rin1
+ …+ Vek
×
--3---0----0---
Rink
(V)
k
Σ ^{Ceq =}
Cin_i
j=1
Cin_i = _2-----×------_π------_×------R----1-_i--_n----_i---_×------F---C-----L----_i (F)
R_eq = ---------¹----------
k
∑ ^----1-----
j =1 ^Rini
In general, for mixed situations (single-ended and differential inputs) it is best to use the
same rule, that is, equalize impedance on both TS4962 inputs.
4.10
Output filter considerations
The TS4962 is designed to operate without an output filter. However, due to very sharp
transients on the TS4962 output, EMI-radiated emissions may cause some standard
compliance issues.
These EMI standard compliance issues can appear if the distance between the TS4962
outputs and the loudspeaker terminal is long (typically more than 50 mm, or 100 mm 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 TS4962 output pins and the
speaker terminals.
● Use ground planes for "shielding" sensitive wires.
● Place, as close as possible to the TS4962 and in series with each output, a ferrite bead
with a rated current of at least 2.5 A and an 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 (see Figure 63).
Figure 63. Method for shorting perturbations to ground
From TS4962 output
Ferrite chip bead
To speaker
about 100pF
Gnd
34/44
Doc ID 10968 Rev 8