RE: [SI-LIST] : which layers should I use for routing my high spe ed traces

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From: Ron Miller (rmiller@brocade.com)
Date: Mon May 07 2001 - 12:19:22 PDT


Saeen

At 644 Mhz, and assuming about 5 mil dielectric thickness the capacitance
per square inch is ~200pf so that the ground and supply
planes are essentially the same. Use whichever layer you like.

Just keep you high speed traces on a layer away from other lines that might
couple non-coherent edges onto your sensitive data, reducing
signal to noise ratio.

Ron Miller

-----Original Message-----
From: Saeen Malik [mailto:saeens@hotmail.com]
Sent: Monday, May 07, 2001 11:38 AM
To: si-list@silab.eng.sun.com
Subject: [SI-LIST] : which layers should I use for routing my high speed
traces

I have the following stackup. I need to route 644 MHz. PECL signals. Which

layers should I use

------------------ gnd
      ---- route layer 1
------------------ gnd
      ---- route layer 2
      ---- route layer 3
------------------ peclpower
      ---- route layer 4
      ---- route layer 5
------------------ gnd
      ---- route layer 6
------------------ gnd

My inclination is to use layers 2,3 and 4,5 because it would provide return

path for
both cases - switching high and low. On the other hand if I use the single
stripline layers,
the return current when the device switched high would have to go through a
cap to enter the power
pin.

What do you people think???

Saeen
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