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

Richard Wilbur richard.wilbur at gmail.com
Thu Oct 12 21:16:45 BST 2017

On Oct 11, 2017, at 19:31, Luke Kenneth Casson Leighton <lkcl at lkcl.net> wrote:
> https://ez.analog.com/docs/DOC-11303
> Each TMDS signal shall have single ended impedance of 50 Ω ± 10%.
> Each TMDS pair shall have differential impedance of 100 Ω ± 5%.
> whoops.... :)  89 ohm... 50 ohm.  89 ohm... 50 ohm.  oops... :)

Well, if the reported impedance is the single-ended impedance of those lines we have considerable margin to burn and should aggressively pursue the taper structure and bring in the keepouts at each end.

For the geometry that fit our constraints, we calculated a single-ended impedance of ~72 Ohm and differential impedance of ~111 Ohm (which corresponds to a tolerance of 11%).

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