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

[Luke Kenneth Casson Leighton]

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.