TS2007_11 Datasheet, PDF (25/29 Pages) STMicroelectronics – 3 W filter-free Class D audio power amplifer with 6-12 dB fixed gain select

TS2007
Application information
4.10
Output filter considerations
The TS2007 is designed to operate without an output filter. However, due to very sharp
transients on the TS2007 output, EMI radiated emissions may cause some standard
compliance issues.
These EMI standard compliance issues can appear if the distance between the TS2007
outputs and loudspeaker terminal are 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 TS2007 output pins and the
speaker terminals.
● Use a ground plane for “shielding” sensitive wires.
● Place, as close as possible to the TS2007 and in-series with each output, a ferrite bead
with a rated current of minimum 2.5 A 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 extra footprint to place, if necessary, a capacitor to short perturbations to ground
(see Figure 51).
Figure 51. Ferrite chip bead placement
From TS2007 output ^{Ferrite chip bead}
to speaker
about 100pF
gnd
In the case where the distance between the TS2007 output and the speaker terminals is too
long, it is possible to have low frequency EMI issues due to the fact that the typical operating
frequency is 280 kHz. In this configuration, it is necessary to use the output filter
represented in Figure 1 on page 4 as close as possible to the TS2007.
Doc ID 13123 Rev 4
25/29