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

Richard Wilbur richard.wilbur at gmail.com
Thu Aug 3 20:04:18 BST 2017

On Thu, Aug 3, 2017 at 9:28 AM, Luke Kenneth Casson Leighton
<lkcl at lkcl.net> wrote:
> On Thu, Aug 3, 2017 at 2:59 PM, Richard Wilbur <richard.wilbur at gmail.com> wrote:
>> What I said earlier is that I would recommend the following geometry
>> for the transmission lines:
>> trace width = 6.5mil
>  there's not enough space.  when i said "there's not enough space" i
> *really meant*, "there's not enough space".  it *might* be possible to
> increase to 5.1 mil but i think you'd agree it would not be worth it.
>  the reason that there's not enough space is because:


Thanks for the explanation.  Sorry, I didn't remember how tight things
were.  I was thinking about how we now have more space--just not that
much more space.

So, I ran some numbers the other direction through the equations to
see what impedance we can expect from the connector lands and smaller
trace sizes without smaller trace separation:

The good news is it looks like we are still within the +/-15% of 100
Ohm.  I'll explain more later.

>  ok i did a video explaining: https://youtu.be/vFbzAmLSHPY

Thanks for the video, I watched the first 55s and thus this reply.
I'll finish watching and then tie up loose ends.

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