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

[Luke Kenneth Casson Leighton]

On Thu, Aug 3, 2017 at 12:37 PM, Richard Wilbur
<richard.wilbur at gmail.com> wrote:


> Here we can see the effect of changing the single-ended impedance on
> width and spacing of traces in a differential pair of given
> differential impedance.  By raising the single-ended impedance we
> reduced both the width of the traces and also the spacing.

 i know from DDR3 that they can change (dynamically) the end-impedance
both on the SoC and in the DDR3 RAM ICs.  it means you can stick with
a particular track width and spacing then have the SoC and DDR3 ICs
adjust each end to suit.


> Toradex mentions the lower impedance between wide traces and the
> reference plane causing impedance mismatch at large pads for
> components and connectors.[21]

 yehyeh.  fortunately the ones on the DC3 connector are tiny.

 i think you're saying we're ok here with 5mil track, 5mil spacing,
and lots and lots of ground vias.  i can't get them in between the
diff-pairs though.

l.