FreeLists / si-list / [SI-LIST] Re: Finding the impedance of a PCB trace

["Graham Davies" <GrahamDavies@xxxxxxxx>]

--- 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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