[SI-LIST] Re: Finding the impedance of a PCB trace
- From: Doug Brooks <doug@xxxxxxxxxx>
- To: GrahamDavies@xxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Mon, 02 May 2005 09:21:07 -0700
As an added reference, the new Polar Quicksolver gives Zo for these
dimensions as 47.38 Ohms
The new UltraCAD differential calculator (single ended calculations are
free) does not allow a value for H less than 4 mils, BUT, you can scale
everything up by a factor of two (check this out with the Polar calculator,
you get the same result) and when you do that the UltraCAD calculator gives
a value for Zo of 48.5 Ohms. The new UltraCAD calculator will also do
differential calculations, but a license is required.
Doug Brooks
At 02:28 PM 4/29/2005, Graham Davies wrote:
>This is, of course, related to my search for a good 6-layer stackup.
>
>What is the impedance of a PCB trace (microstrip) with the following
>parameters:
>Width ......................... 6.00 mil
>Height above return plane ..... 3.20 mil
>Thickness ..................... 1.35 mil (1 ounce copper)
>Dielectric rel. permittivity .. 4.2
>
>These are the answers I get from various tools:
>
>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=util_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)
>
>Does anyone have an idea as to why these calculators give results
>that vary by 20% and which are more reliable?
>
>Graham.
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