[SI-LIST] Re: PCI-E, Zdiff and Er

  • From: "Mike Heimlich" <mike@xxxxxxxxxxx>
  • To: <luc.durand@xxxxxxxxxx>, <roymesi@xxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
  • Date: Wed, 16 Nov 2005 09:11:00 -0800

Hi roy:

You can go to www.appwave.com/download and get a free tool called TxLine
that will help you design your diff lines given the dielectric constant
and thickness of the board.=20

If you have problems with this, let me know.

Regards,
MikeH


-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Luc Durand
Sent: Wednesday, November 16, 2005 6:45 AM
To: roymesi@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: PCI-E, Zdiff and Er

Hello Roy,

I have not read the PCI-E spec but I am surprised it would ask for
specific track widths/distances if they do not specify the dialectric as
well since woth are related. My guess is the spec asks for a Zohms of
100 ohms and it is up to you to calculate the proper width/distance by
the dialectric you wish to use.

Regards

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Roy M
Sent: Wednesday, November 16, 2005 3:51 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] PCI-E, Zdiff and Er


Hi Everyone,
I'm designing a PCI-E board and trying to figure out what the Er
(dielectric
constant) should be in order to achieve the 5-5-5 width-space demand for
PCI-E and the Zdiff=3D3D100ohm (i found out that 5-5-5 is the demand for
PCI-E traces - could anyone confirm that???).
i tried to find in the internet something related to Er for PCI-E but
couldn't find anything. I did find though that the standard width of the
add on card is 63mil (1.6mm), but regarding the Er - zippo.
 What kind of substrate is better to achieve the 5-5-5? (i mean FR4 of
Er=3D3D
4.2 or maybe something else...)
Maybe somone here designed other space-width ratio and achieved
Zdiff=3D3D100ohm? because i didn't succeed... what i got for Er=3D3D3.8 =
was
4-8-4
and not 5-5-5
  Thanks,
Roy
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