That's fair ... In which case we'd need to ask what the fastest speed on the
board is ... You could easily run 100MHz on a standard loss material.
Bill Hargin
425-301-4425
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Carson Au
Sent: Wednesday, February 22, 2017 12:42 PM
To: billh@xxxxxxxxxxxxx
Cc: corley@xxxxxxxxx; lists@xxxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx;
si-list-bounce@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: common PCB material for routing refclk in PCIe4
designs?
Doesn't the question call for REFCLK routing of PCIe Gen4, rather than the
actual SERDES channels? In that case, the reference clock is 100MHz, maximum
slew rate 4V / ns. That should not require any particular laminates to meet
jitter requirements.
On Thu, Feb 23, 2017 at 7:03 AM, Bill Hargin (Nan Ya, USA) <
billh@xxxxxxxxxxxxx> wrote:
As I understand it PCIe4 is running at 16 Gbps, so the comments aboutcan survive.
PCIe3 don't apply, since it's running at half that speed.
You need to consider the run length, of course, and consider
simulating with different loss tangents to get an idea of what your eyes
FR408HR isn't a bad material, but with Df~0.010 range, I'd say that
it's more suited to PCIe3 than 4. Without a repeater or pretty short
run lengths, I would think that you're looking at a more expensive
material down in the Df~0.0045 range. Megtron 6 or a Meg6 lookalike
might be in order, although you'll be paying for the lower loss.
You would also need to consider whether you're building in the US or
in Asia, as well. Availability is significantly different when you
cross the pond.
P.S. Small caveat to the "NP-175" statement below. (NP=Nanya
Plastics.) The actual product name is "NP-175FM," and I wouldn't use
it for PCIe3 or PCIe4, as its Df is in the neigborhood of 0.0175.
Bill Hargin
Director of North American Sales and Marketing Nan Ya Copper-Clad
Laminates
billh@xxxxxxxxxxxxx ⪠425-301-4425 ⪠Skype: bill.hargin
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Chuck Corley
Sent: Tuesday, February 21, 2017 10:31 PM
To: lists@xxxxxxxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx; si-list-bounce@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: common PCB material for routing refclk in PCIe4
designs?
To be a bit more precise, I'd probably group them this way:
Medium speed / lowest cost:
370HR
NP175
Higher speed / moderately lower cost:
N4000-13
FR408HR
As someone else also mentioned, FR408HR would probably be an excellent
choice.
Chuck Corley
National Instruments
On 2017-02-21 22:25, Chuck Corley wrote:
Many people who will be implementing PCIe 4.0 will be doing it for
PCs or for markets that want to minimize cost so I would suggest
looking at something on the less expensive end of the spectrum like
FR408HR or 370HR or NP175. All 3 of these are moderately lower loss
and less expensive.
Chuck Corley
National Instruments
On 2017-02-21 17:11, 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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