Hi Gary,
Look into the physical Layer spec, there should be some information about the
Losses (maybe hidden in Eye Masks). The maximum allowed loss gives the best
starting point for material selection. Then define the impedance cell based on
routing restrictions (e.g. Pinfields...). With Material and tracewidth you can
calculate the max. Tracelength you can tolerate. If you need more tracelength,
then change to a lower loss material.
For "Low cost FR4" I must say that there a huge performance differences from
vendor to vendor. Look at the datasheets and choose one with low dispersion to
lower the energy consumption of your circuit (FFE and DFE are quite hungry).
BR
Gert
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-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On ;
Behalf Of Gary Giust
Sent: Wednesday, February 22, 2017 2:12 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] common PCB material for routing refclk in PCIe4 designs?
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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