Layout Considerations For The Cs8900; General Guidelines; Power Supply Connections - Cirrus Logic CRYSTAL LAN CS890 Technical Reference Manual

2.4 Layout considerations for the
CS8900
The CS8900 is a mixed signal device hav-
ing digital and analog circuits for an Ether-
net communication. While doing the PCB
layout and signal connections, it is impor-
tant to take the following precautions:
a) Provide a low inductive path to reduce
power and ground connection noise.
b) Provide proper impedance matching
especially to the Ethernet analog signals.
c) Provide low inductive path, wider and
short traces, for all analog signals.
It is important that a PCB designer follow
suggestions made in this document for
proper and reliable
CS8900. These guidelines will also benefit
the design with good EMI test results.
AN83REV1
operation of the
CS8900 Technical Reference Manual

2.4.1 General guidelines

Figure 2.4.1 shows component placement
for an ISA COMBO Ethernet adapter card
using a CS8900.
CS8900 should be such that the routes of
the analog signals and the digital signals
are not intermixing. No signal should route
beneath the CS8900 on any plane.

2.4.2 Power supply connections

The CS8900 has 3 analog and 4 digital
power pin pairs (Vcc and GND). Addi-
tional ground connections are provided.
Each power pin pair should be connected to
a 0.1 µF bypass capacitor. Connect the
extra ground pins directly the ground plane.
The placement of the
33