SNOSAX1F May 2008 – September 2015 DP83849I
The device VDD supply pins must be bypassed with low-impedance 0.1-μF surface mount capacitors. To reduce EMI, the capacitors must be places as close as possible to the component VDD supply pins, preferably between the supply pins and the vias connecting to the power plane. In some systems it may be desirable to add 0-Ω resistors in series with supply pins, as the resistor pads provide flexibility if adding EMI beads becomes necessary to meet system level certification testing requirements. (See Figure 7-1) It is recommended the PCB have at least one solid ground plane and one solid VDD plane to provide a low impedance power source to the component. This also provides a low impedance return path for non-differential digital MII and clock signals. A 10.0-μF capacitor must also be placed near the PHY component for local bulk bypassing between the VDD and ground planes.