GS2971A Datasheet, PDF (146/152 Pages) Gennum Corporation – Integrated audio clock generator

5. Application Reference Design
5.1 High Gain Adaptive Cable Equalizers
The GS2971A has an integrated adaptive cable equalizer. In order to extend the cable
length that an equalizer will remain operational at, it is necessary for the equalizer to
have high gain.
A video cable equalizer must provide wide band gain over a range of frequencies in
order to accommodate the range of data rates and signal patterns that are present in a
SMPTE compliant serial video stream.
Small levels of signal or noise present at the input pins of the GS2971A may cause
chatter at the output. In order to prevent this from happening, particular attention must
be paid to board layout.
5.2 PCB Layout
Special attention must be paid to component layout when designing Serial Digital
Interfaces for HDTV. An FR-4 dielectric can be used, however, controlled impedance
transmission lines are required for PCB traces longer than approximately 1cm. Note the
following PCB artwork features used to optimize performance:
• PCB trace width for 3Gb/s rate signals is closely matched to SMT component width
to minimize reflections due to change in trace impedance.
• The PCB ground plane is removed under the GS2971A input components to
minimize parasitic capacitance.
• High speed traces are curved to minimize impedance changes.
GS2971A 3Gb/s, HD, SD SDI Receiver
Data Sheet
54311 - 2
September 2012
146 of 152