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

[Richard Wilbur]

Regarding the taper, I am sure we don't want to reduce the spacing
over a long enough distance to reduce the impedance below the HDMI
tolerance:
differential = 100 +/-15% Ohm = [85,115] Ohm,
single-ended = 55 +/15% Ohm = [42.5,57.5] Ohm.

What does PADS report for the impedance of our HDMI differential
traces on the current or a recent layout?

(We opened up the clearance to 15mil around the differential pairs in
order to try to keep the impedance up.)  If the impedance is too low,
we may need to forgo the taper altogether and just live with the small
discontinuities caused by a few vias and component lands that are
significantly closer.