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

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On Thu, Aug 3, 2017 at 11:53 PM, Richard Wilbur richard.wilbur@gmail.com wrote:

We can still take some of the recommendations to heart:

1. Use minimal size vias for high-frequency traces to reduce

parasitic capacitance.[23]

yep. 0402 all the way round. can't go smaller as it risks the drill hitting the edge of the ring.

2. Place the two vias of the differential pair in close proximity to

increase capacitive coupling between the signals.(smaller via pitch)

yep. doing that.

3. Instead of using two separate anti-pads on signal vias, combine

them into an oval shared antipad (on every layer) to reduce parasitic capacitance.

oo. never heard of this practice. never heard of "anti-pads" either! so sorry, if you put some references i missed them.

4. Place ground vias next to signal vias to provide low-impedance

ground-return paths.[22, Figure 2]

yep doing that.

l.