[SI-LIST] Re: Finding the impedance of a PCB trace
- From: "Hargin, Bill" <bill_hargin@xxxxxxxxxx>
- To: <GrahamDavies@xxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Mon, 2 May 2005 09:57:42 -0700
This is getting interesting. =20
If I understood your stackup properly, Graham, I come up with a
significantly different value with HyperLynx's 2D field solver. I get
54.4 Ohms. I'll send you a jpg of the stackup I'm looking at offline,
and maybe you can tell me whether I've got it right.
Why the 20% variation amongst the equation-based solvers? ... An
interesting question for someone with the time to investigate would be
where the equation-based results are breaking down. Eric Bogatin and
others have compared the HyperLynx field solver with both Ansoft and
bench measurements, finding the results to be within 1 percent across a
wide range of standard PCB dimensions. =20
Doug commented:
"As an added reference, the new Polar Quicksolver gives Zo for these
dimensions as 47.38 Ohms" ...=20
So, that would be a 12 percent variation between the two field solvers
here. =20
Can you run this in LineSim, Doug, and see if you get the same results
that I do?
Bill Hargin
Product Manager - HyperLynx
Mentor Graphics Corp.
425-497-5079 - Direct
425-301-4425 - Mobile
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx=20
> [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Graham Davies
> Sent: Friday, April 29, 2005 2:29 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Finding the impedance of a PCB trace
>=20
> This is, of course, related to my search for a good 6-layer stackup.
>=20
> What is the impedance of a PCB trace (microstrip) with the following
> parameters:
> Width ......................... 6.00 mil Height above return=20
> plane ..... 3.20 mil Thickness ..................... 1.35 mil=20
> (1 ounce copper) Dielectric rel. permittivity .. 4.2
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> These are the answers I get from various tools:
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> 41... ohms (http://www.icd.com.au/)
> 41.69 ohms (http://www.emclab.umr.edu/pcbtlc/microstrip.html)
> 41.69 ohms (TraceSim version 1.0.0)
> 41.69 ohms (http://www.technick.net/public/code/cp_dpage.php?
> aiocp_dp=3Dutil_pcb_imp_calculator)
> 41.7 .ohms (http://www.sunmantechnology.com/resources/cal_cat00.shtml)
> 46.14 ohms (ZTOOL Impedance Calculator V1.2)
> 47.31 ohms (http://www.rogers-corp.com/mwu/mwi_java/mwij_vp.html)
> 50.89 ohms (http://www.csgnetwork.com/boardrunimpcalc.html)
> 51.27 ohms (TxLine version 1.1)
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> Does anyone have an idea as to why these calculators give=20
> results that vary by 20% and which are more reliable?
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> Graham.
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