About HDMI Signal Routing Requirements

[UNA_H]

Hi,

I have the following questions regarding the AGX HDMI routing requirements.

Q1: The Jetson AGX Xavier Series OEM Product Design Guide p72 contains the following.
"For Stripline, this is 3x of the thinner of above and below. "
What exactly does “the thinner of above and below” mean? Which part is thinner?

Q2: Does the Max Total Delay item indicate a maximum wiring length requirement?
For example, Stripline requires 63.5mm, which seems to be a severe restriction.
Is this requirement a correct requirement?

Q3: What does “5x spacing” or “7x spacing” mean?

Best Regards,
UNA

[UNA_H]

Hi,

I would be happy to hear from anyone familiar with NVIDA who would like to comment on this question.

Best Regards,
UNA

[Trumany]

Q1, it means the thinner of above/below layer of PCB board.
Q2, Yes, it is for delay and so get the trace length limit.
Q3, 5x/7x is corresponding to the Trace spacing (Pair-Pair).

[UNA_H]

Hi Trumany,

Thank you for your reply.

Q3, 5x/7x is corresponding to the Trace spacing (Pair-Pair).

Please explain in more detail as I do not understand correctly what is being described.
Does this indicate a case where Trace spacing is 5x (7x) for “the length of which part”?

Best Regards,
UNA

[Trumany]

When you use 5x or 7x trace spacing microstrip, your trace length (max total delay) should be the value as marked with 5x or 7x.

[UNA_H]

For example, does the diagram below specify the trace length when “W (Microstip wide)” is 5x (or 7x) larger than “S (Trace space)”?

Best Regards,
UNA

[Trumany]

When S is 5x (or 7x) dielectric, the total max total delay (trace length) should be 300ps (or 350ps).

[UNA_H]

I am confused. Where is it 5x(or 7x) against?
You mean 300 ps when S is 5x longer than W, right?

[Trumany]

Sorry, if S is the spacing between P and N lines, then it has nothing to do with “S” and “W” in your picture.

[EDITED]
The 5x/7x is the spacing (dielectric) of pair to pair. If your design is 5x spacing microtrip, then you should control the total trace length of each HDMI pair < 50.8mm(300ps), if it’s 7x design, you should control that < 63.5mm(375ps). Is it clear?