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

[Luke Kenneth Casson Leighton]

hiya richard, so how you getting on?
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On Fri, Oct 13, 2017 at 1:56 AM, Luke Kenneth Casson Leighton
<lkcl at lkcl.net> wrote:
> On Thu, Oct 12, 2017 at 9:16 PM, Richard Wilbur
> <richard.wilbur at gmail.com> wrote:
>
>>> 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.
>
>  i sort-of understand that.  am i right in thinking: at the ends we
> have to treat them as single-ended, and achieve a sngle-ended
> impedance of 50 ohms, but 100 ohms for the diff-pairs.
>
>> 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%).
>
>  ok so 72's not really very close to 50 ohms... interested to learn
> how that can be achieved.
>
> l.