Texas Instruments TPA005D02 - Manual (Page 26)

The TPA005D02 Audio Power Amplifier Evaluation Module
3-12 Details
3.2.3.4 Ground Plane
Experimentation with several types of ground planes has shown that a solid
ground plane works as well as methods that split the analog and power ground
planes when good layout practices are followed. This allows a much simpler
design that requires less time and is less prone to layout errors. The success
of the solid ground plane is partially due to the TPA005D02 IC, which allows
the designer to keep the input and output sections of the chip separated,
reducing the chance that high- and mid-frequency return currents will make a
path to the analog input section of the chip.
The traces for the analog circuit grounds are extremely short and are
connected to the ground immediately under the chip through vias, while the
power circuit grounds are connected to the ground plane slightly further out
from the chip and closer to the signal outputs and power inputs. The large
current traces of the output are then shielded from the input circuit by the
ground plane.
The solid ground plane has low resistance compared with the narrow paths to
pins and vias that are attached. If a voltage spike or current spike hits the
ground plane, the entire plane shifts up or down, unlike a split plane, which has
inductance between the halves that dampens the noise and can cause uneven
voltage potentials to exist.
3.2.3.5 Compensation, Ramp Generator, and Charge Pump Capacitors
The components (C19, C5, C4 and C8) for these circuits are critical to the
operation of the TPA005D02 amplifier. The capacitance at these nodes must
be close to the specified value and maintain this value over EVM temperature
extremes. Ceramic capacitors with X7R temperature characteristics should be
used for their low ESR and their stability over a wide temperature range. Tight
tolerances are needed, especially for RCOMP (C4) and LCOMP (C8), which
need to track closely for good left and right channel matching. A high voltage
rating is not needed (15 V would work), yet 50 V is one of the lowest ratings
for the size and type of capacitor selected.
Ramp generator capacitor C5 does not need the tight capacitance value
tolerance that C4 and C8 require; however, capacitance stability over
temperature change is important.
Charge pump capacitor C19 has the same requirements as the ramp
generator capacitor (C5), though the size is much larger and the necessary
voltage rating due to the charge tripling is increased, making the part
somewhat less readily available.