Datasheet

Data Sheet ADAU1772
Rev. B | Page 49 of 116
APPLICATIONS INFORMATION
POWER SUPPLY BYPASS CAPACITORS
Each analog and digital power supply pin should be bypassed to
its nearest appropriate ground pin with a single 0.1 μF capacitor.
The connections to each side of the capacitor should be as short
as possible, and the trace should be routed on a single layer with no
vias. For maximum effectiveness, locate the capacitor equidistant
from the power and ground pins or slightly closer to the power pin
if equidistant placement is not possible. Thermal connections to
the ground planes should be made on the far side of the capacitor.
Each supply signal on the board should also be bypassed with a
single bulk capacitor (10 μF to 47 μF).
Figure 94. Recommended Power Supply Bypass Capacitor Layout
LAYOUT
Pin 24 is the AVDD supply for the headphone amplifiers. If the
headphone amplifiers are enabled, the PCB trace to this pin should
be wider than traces to other pins to increase the current carrying
capacity. A wider trace should also be used for the headphone
output lines.
GROUNDING
A single ground plane should be used in the application layout.
Components in an analog signal path should be placed away
from digital signals.
EXPOSED PAD PCB DESIGN
The ADAU1772 has an exposed pad on the underside of the
LFCSP. This pad is used to couple the package to the PCB for
heat dissipation. When designing a board for the ADAU1772,
special consideration should be given to the following:
• A copper layer equal in size to the exposed pad should be
on all layers of the board, from top to bottom, and should
connect somewhere to a dedicated copper board layer (see
Figure 95).
• Vias should be placed to connect all layers of copper,
allowing for efficient heat and energy conductivity. For an
example, see Figure 96, which has nine vias arranged in a
3 × 3 grid in the pad area.
Figure 95. Exposed Pad Layout Example, Side View (Not to Scale)
Figure 96. Exposed Pad Layout Example, Top View (Not to Scale)
VDD
GND
TO GND
TO VDD
CAPACITOR
10804-086
TOP
POWER
GROUND
BOTTOM
COPPER SQUARESVIAS
10804-087
10804-088