Re: [SI-LIST] : differential impedance....NEED your feedback

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From: AYYANU,VAIRAMUTHU (A-Singapore,ex2) (vairamuthu_ayyanu@agilent.com)
Date: Mon Jun 12 2000 - 17:47:15 PDT


Hi Jenkins,

I have the same issue i.e. FC signals to have differential Zo = 150 ohms
(stripline if possible?)

Here is my thinking:

>>>>> SHOULD USE "BT" MATERIAL or other equivalent material that has a
diectric constant = 3.5. If you refer to
http://swan.automata.com/cgi-bin/imped-sl, you get the follwing data

I. Automata's Stripline Impedance and Capacitance Modeling

You submitted the following name/value pairs:
Er = 3.5
h = 16 (i.e. ground plane to ground plane separation)
t = .5 Oz
w = 3
The characteristic impedance = 74 Ohms (diff Zo = 2x75 = 150 ohm)
The intrinsic line capacitance = 1.6 pF/inch

>>>>> If we use FR-4, the dimensions are becoming out of limit for strip
line. Let me know if you have any final configuration/recommendation.

Regards,
Vairamuthu

Principal Development Engineer,
HSIO dept, Agilent Technologies S'pore Pte Ltd.,
SCO, 1150 Depot Road,
Singapore 109673

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Re: [SI-LIST] : differential impedance
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From: Mike Jenkins (jenkins@lsil.com)
Date: Thu Apr 20 2000 - 11:29:41 PDT

Next message: MikonCons@aol.com: "Re: [SI-LIST] : 20-H Rule and
Self-Resonant Frequency of Power Planes"

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Sean,

Based on experience with Fibre Channel PCB layouts, 150 ohm dif'l striplines will require some pretty thick dielectrics and some pretty thin lines. I believe it's doable, but will dictate some trade-offs on the cross section.

Good luck, Mike

> > We currently have an application that requires some signals to > be 150 ohms (stripline if possible?); with them being routed as > differential pairs so that their impedance is 75 ohms. Anyone have any > experience with this as stripline. We have done them as microstrip > before and at 100/50 stripline, but never 150/75. > > Regards, > Sean Murray > Sales Manager > > M&M Specialties Inc. > 1236 W. Southern Ave. #106 > Tempe, AZ. 85282-4518 > Phone: (480) 858-0393 x105 > Cell: (602) 684-7859 > Fax: (480) 858-1882 > Email: seandm@mmspec.com > WWW.mmspec.com

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