differential pair of 8o ohms for a usb io PCB
differential pair of 8o ohms for a usb io PCB
(OP)
I have never needed to do a differential pair myself but the schematic calls out for one. The data sheet says it needs to be 80 differential between the two traces. Reading tutorials on it tell me that the this can be determine by trace width height and permeability of the dielectric. I found two approaches on this stripline and microstrip. I am confused on the advantages of which one to use. Can some elaborate on this?





RE: differential pair of 8o ohms for a usb io PCB
Wikipedia has the following:
http://en.wikipedia.org/wiki/Stripline
http://en.wikipedia.org/wiki/Microstrip
In your specific case, you'd want something slightly different, I think, which is that you want the characteristic impedance BETWEEN the two lines to be the value desired. This would normally entail running one of the two lines on top of the other.
TTFN
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RE: differential pair of 8o ohms for a usb io PCB
Dan - Owner

http://www.Hi-TecDesigns.com
RE: differential pair of 8o ohms for a usb io PCB
RE: differential pair of 8o ohms for a usb io PCB
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Once you get it running, go to:
Design Type > Microstrip > Edge Coupled
Pick your board material (you can input the board properties manually if you're using someone else's material). Then you can vary the height, width, spacing etc until you reach the right differential impedance.
Peter
RE: differential pair of 8o ohms for a usb io PCB
RE: differential pair of 8o ohms for a usb io PCB
Orientation of the connector isn't an issue as long as your impedance and signal length are within spec. At high speeds, placing it on a piggy-back connector could present issues...
Dan - Owner

http://www.Hi-TecDesigns.com
RE: differential pair of 8o ohms for a usb io PCB
RE: differential pair of 8o ohms for a usb io PCB
Dan - Owner

http://www.Hi-TecDesigns.com
RE: differential pair of 8o ohms for a usb io PCB