11.1 Layout Guidelines

Figure 38 shows a typical PCB floor plan for the PCM175x devices. 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 PCM175x should 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 PCM175x. In cases where a common 5-V supply must be used for the analog and digital sections, an inductance (RF choke, ferrite bead) should be placed between the analog and digital 5-V supply connections to avoid coupling of the digital switching noise into the analog circuitry. Figure 39 shows the recommended approach for single-supply applications.