3.0 PC Board Considerations
CX25870/871
3.2 Power and Ground Planes
Flicker-Free Video Encoder with Ultrascale Technology
3.2 Power and Ground Planes
For optimum performance, a common digital and analog ground plane and a
common digital and analog power plane are recommended. The power plane
should provide power to all CX25870/871 power pins, reference voltage (VREF)
circuitry, and COMP decoupling.
The CX25870/871 power plane should be connected to the graphics system
power plane (VCC) at a single point through a ferrite bead, as illustrated in
Figures 3-1 and 3-2. This bead should be located within 3 inches of the
CX25870/871. The bead provides resistance to switching currents by acting as a
resistor at high frequencies. A low-resistance bead should be used, such as
Ferroxcube 5659065-3B, Fair-Rite 2723021447, or TDK BF45-4001. See
Table 3-1 for a typical parts list for key passive components.
Figure 3-1. Power Plane Illustration
Bracket
3.3 V
Composite #1
Luma
Chrome
Composite #2
S-Video
CX25870
Ferrite Bead
o VCC3.3
3.3 VAA-CX870
Oscillator
Analog
Conexant
(Bt835)
Video
o VCC3.3
Data
Decoder
5V
Clocks
TOP
Signals
GND
PWR
4 layer board
plane order:
PCI or AGP Connector
Signals
BOTTOM
100381_017
3-2
Conexant
100381B
CONEXANT [ CONEXANT SYSTEMS, INC ]
