[SI-LIST] Re: Finding the impedance of a PCB trace
- From: "Graham Davies" <GrahamDavies@xxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Mon, 02 May 2005 22:39:32 -0000
--- In si-list@xxxxxxxxxxxxxxx, "Hargin, Bill" <bill_hargin@xxxx> wrote:
> ... with HyperLynx's 2D field
> solver ... I get 54.4 Ohms.
> I'll send you a jpg of the
> stackup ...
It probably makes no difference that your second layer down is VCC
instead of ground, so yes, the top layer is what I have.
Just to complete the picture, the layer order (thanks to Steve) is SGP
SGS where S is a signal layer, G is a ground plane layer and P is a
gridded power layer. The separations, in the same order, are 3.2, 4.0,
38, 4.0 and 3.2 mil. Most traces are 6 mil wide routed on a 12.5 mil
grid. All copper is 1 ounce, which various sources give as 1.3 or 1.4
mil, hence my use of 1.35 mil. I just had to plump for an Er and picked
4.2.
It's nice to know what HyperLynx thinks because when I do finally shake
some cash loose here some of it will go in Mentor's direction. If I
have to pick a tool to believe, it might as well be the one I have the
best chance of buying.
Graham.
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