[Arm-netbook] HDMI High-Frequency Layout: Goals

Richard Wilbur richard.wilbur at gmail.com
Thu Aug 3 09:50:57 BST 2017

HDMI Layout Notes
for EOMA68 Cards
by Richard Wilbur


The portion of the HDMI transmission path contained on the PCB has
several goals:
    1.  Support all operating modes of the HDMI v1.4 interface of
which the A20 chip is capable (clock up to 340MHz, data up to 3.4GHz).
    2.  Match the characteristic impedance of the rest of the HDMI
transmission path (connectors, cable, and receiver) to minimize
reflections and deliver a recoverable/decodeable signal to the
receiver.  [low distortion, sufficient amplitude]
    3.  Minimize radiated Electro-Magnetic Interference which could
adversely effect other circuits on the EOMA68-A20 or in its
surroundings, or exceed regulatory limits of concerned agencies:  FCC,
CSA, etc.
    4.  Minimize sensitivity to EMI from other circuits on the
EOMA68-A20 and its surroundings.

Of these goals careful layout realizing a microstrip geometry helps
with minimizing EMI radiation and sensitivity, while impedance
matching both minimizes signal reflections which distort the
transmitted signal and delivers the signal energy to the intended

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