Correct. To keep things realistic, I'm just trying to use a material
that is representative of what actual PCIe4 designs will use (which I
expect will be driven by the SERDES, rather than the refclk,
requirements).
On 2017-02-22 12:42, Carson Au wrote:
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 about
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 can
survive.
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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