Thanks everyone for your recommendations and comments (really appreciate
it). Sounds like FR408HR is a good choice to represent low-cost yet
realistic PCIe4 designs.
Vinu, the spec does limit the edge rate for reference clocks (between
0.6 and 4 V/ns) measured at the output of the 12" trace, but as I'm an
independent test lab selling compliance reports to PCIe4 reference-clock
vendors, I'll need to accommodate a variety of devices with different
edge rates.
It is interesting to note though, if a company fails the edge rate test
using a 12" FR408HR, a lower-loss material may result in their device
passing this test. Thus, my interest in trying to choose a material that
is realistic for PCIe4 designs, without being too low loss.
Best regards, Gary
On 2017-02-22 10:35, Vinu Arumugham wrote:
Gary,------------------------------------------------------------------
Does the spec. provide an edge rate limit? You would want to pick the
material that brings you closest to the slowest edge rate allowed, to
perform a good stress based evaluation.
Thanks,
Vinu
On 02/21/2017 05:11 PM, Gary Giust wrote:
Hi, I'm designing a test board to evaluate reference clocks for PCIe
4.0
market. The standard calls for a 12" differential 100 Ohm trace, but I
don't think it specifies the PCB material (FR4, Rogers, Tachyon,
Nelco-13, Megtron-6, etc.) to use.
Since I have to pick a material, I'm looking for recommendations which
one would be realistic (although perhaps on the pessimistic side) for
actual PCIe 4 designs. I want to avoid picking a material that is
clearly too high loss, or too low loss, compared to what may actually
be
used.
Any recommendations?
Best regards, Gary
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