High-Power Stereo Class-D Audio Power Amplifier
SGM4703 with Adjustable Power Limit and Automatic Level Control
28
DECEMBER 2022
SG Micro Corp
www.sg-micro.com
PCB LAYOUT
As a high power, high efficiency, Class-D stereo audio
power amplifier, the SGM4703 requires proper PCB
layout and grounding to ensure high efficiency, low
distortion, and low EMI emission. Use wide traces for
the power supply inputs (PVDD) and audio outputs
(VOPL/R and VONL/R) to minimize losses due to
parasitic trace resistances. Route all traces that carry
switching transients away from the traces or
components in the audio signal path.
Ground Plane – It is required to use a solid metal
plane with sufficiently wide area as a central ground
GND for SGM4703. All the power ground pins PGND
are directly shorted to the large ground plane GND,
which serves as a central “star” ground for the
SGM4703. Use a single point of connection between
the analog ground AGND and the ground plane GND to
minimize the coupling of high-current switching noise
onto audio signals.
Supply Decoupling Capacitors – The supply
decoupling capacitors (C
PVDD
and C
AVDD
) should be
placed as individually close as possible to PVDD and
AVDD pins.
Output Filters – Place each audio output filter (ferrite
bead or LC filter) individually close to their respective
output pins, VOPL/R and VONL/R, for best EMI
performance and operational robustness. Keep the
current loop from each of the audio outputs through the
output filters and back to the PGND pins as short and
tight as possible.
Power Dissipation – The maximum output power of
SGM4703 can be severely limited by its thermal
dissipation capability. To ensure the device operating
properly and reliably at maximum output power without
incurring over-temperature shutdown, the following
guidelines are given for best thermal dissipation
capability:
● Fill both top and bottom layers of the system board
with solid GND metal traces.
● Solder the thermal pad directly onto a grounded
metal plane.
● Place lots of equally-spaced vias underneath the
thermal pad connecting the top and bottom layers of
GND. The vias are connected to a solid metal plane
on the bottom layer of the board.
● Reserve wide and uninterrupted areas along the
thermal flow on the top layer, i.e., no wires cutting
through the GND layer and obstructing the thermal
flow.
● Avoid using vias for traces carrying high current.
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