100600B
Conexant
4-1
4
4.0 PC Board Layout Considerations
4.1 Layout Considerations
The PC board layout should be optimized for lowest noise on the Fusion 878A
power and ground lines. Route digital traces away from analog traces. All shields
must be connected to the ground plane with low impedance connection. Use
shielded connectors.
4.1.1 Capacitors
From the following pins to ground, place bypass capacitors as close to the Fusion
878A as possible (using 0.1 µF ceramic capacitors):
Additionally, place bypass capacitors from all other voltage pins to ground
(using 0.1 µF ceramic capacitors) as close to the Fusion 878A, where possible.
Also, whenever possible, place traces from all power pins to a bypass capacitor on
the component side, in addition to any feed-through. Finally, place traces from all
ground pins to a bypass capacitor on the component side, in addition to any
feed-through, when possible.
Ensure that there is ample ground plane under the Fusion 878A. Make wide
paths of copper under and around the Fusion 878A, if possible. Avoid creating a
cut in the plane with feed-throughs instead, disperse them. Also ensure that there
is ample power plane under the Fusion 878A. Make wide paths of copper under
Table 4-1. Capacitor Location
VBB
Pin 95
(1)
VBB
Pin 101
(1)
VAA
Pin 110
VAA
Pin 115
VAA
Pin 117
NOTE(S):
(1)
These pins should be tied to the same voltage as analog
source device.