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

Richard Wilbur richard.wilbur at gmail.com
Fri Aug 11 00:37:35 BST 2017

On Wed, Aug 9, 2017 at 7:23 AM, Luke Kenneth Casson Leighton
<lkcl at lkcl.net> wrote:
> next set...
> wiggles.jpg is the layer 6 length-matching area: HX2N/P is the one
> that's the longest, it snakes back on itself.  i length-matched all 3
> signal pairs to 56.413, and left the CK lines at 57.134 just to give
> the tiniest bit of delay (TI recommendations iirc).

Very nicely done!  57.134mm - 56.413mm = 721um
=> T(delay) = 721um / 150um/ps = 4.8ps

That is a very tiny delay!  Now that we have achieved such close
synchronization, I'm suggesting we go for the next goal where we
design a certain amount of inter-pair skew into the layout for
purposes of lowering the strength of our synchronized pulsing data
lines to a more diffuse chatter.

> no - not even enough space to do 5.1mil / 5.0 clearance... just...  too much.

I understand.  We might end up with more room--see discussion below.

> the other images show the via'd portions, they're all either
> symmetrical or perfectly length-matched to 0.001mm.

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