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

Luke Kenneth Casson Leighton lkcl at lkcl.net
Fri Aug 11 07:12:45 BST 2017

On Fri, Aug 11, 2017 at 12:37 AM, Richard Wilbur
<richard.wilbur at gmail.com> wrote:

> 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!

 ooooOoo :)

>  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.

 *deep breath*.... aaaaaaaa! :)

 well.... that actually happens for the majority of the length in the
middle (starting layer 6)

 but.... if i simply *take out* the intermediary wiggles on layer 6....

>> 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.

 which has probably been truncated...

>> the other images show the via'd portions, they're all either
>> symmetrical or perfectly length-matched to 0.001mm.
> Again, they look nice.<div id="DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2">

 whoops.... something melted there...

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