Datasheet

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SLES071B − MARCH 2003 − REVISED NOVEMBER 2006
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54
CONSIDERATIONS FOR APPLICATION CIRCUITS
PCB Layout Guidelines
A typical PCB floor plan for the PCM1791A is shown in Figure 64. A ground plane is recommended, with the analog
and digital sections being isolated from one another using a split or cut in the circuit board. The PCM1791A must
be oriented with the digital I/O pins facing the ground plane split/cut to allow for short, direct connections to the digital
audio interface and control signals originating from the digital section of the board. Separate power supplies are
recommended for the digital and analog sections of the board. This prevents the switching noise present on the digital
supply from contaminating the analog power supply and degrading the dynamic performance of the D/A converters.
In cases where a common 5-V supply would be used for the analog and digital sections, an inductance (RF choke,
ferrite bead) must be placed between the analog and digital 5-V supply connections to avoid coupling of the digital
switching noise into the analog circuitry. Figure 65 shows the recommended approach for single-supply applications.
Digital Logic
and
Audio
Processor
Digital Power
+V
D
DGND
Digital Section Analog Section
Return Path for Digital Signals
Analog Power
+V
S
AGND −V
S
+5VA
Digital
Ground
Analog
Ground
Output
Circuits
PCM1791A
AGND
V
CC
V
DD
DGND
REG
Figure 64. Recommended PCB Layout