I have laid out this board that includes (among other lower speed connections) a 1 upstream and 2 downstream ports on a 0.5mm FR4. The USB differential traces are 0.6mm wide with 0.15mm spacing between them. Can you give your opinion if this is going to work?

It's an open-source project, here is the link : https://tools.upverter.com/eda/#tool=pcb,designId=6f8c466dba06e940

Thanks for you time.

  • \$\begingroup\$ What does your fab say you should do for 90 ohm controlled impedance? Are those values the result of a PCB impedance calculator? Is there a ground plane on the other side? \$\endgroup\$
    – pjc50
    Apr 13, 2016 at 11:00
  • \$\begingroup\$ Having looked (slowly) at your PCB,it looks like they're short enough that it will make little difference unless you're trying to push the full 5m USB cable length. I can't see any ESD protection which may be a problem in production. See also electronics.stackexchange.com/questions/41851/… \$\endgroup\$
    – pjc50
    Apr 13, 2016 at 11:06
  • \$\begingroup\$ Thank you for your comments. The values are a result of this PCB impedance calculator, eeweb.com/toolbox/edge-coupled-microstrip-impedance, and yes in the bottom copper (which I guess you have already seen there is a ground pour). The ESD protection devices are the ones just after every USB connector (TI SN75240PWR), except if I am understanding sth completely wrong :) . \$\endgroup\$
    – aletsoup
    Apr 13, 2016 at 14:18

1 Answer 1


You can check the line impedance on many WEB sites, for example: http://www.hughescircuits.com/index.php/en/support/impedance-calculator

However: the impedance matching becomes important when the line length is longer than 5-10% of wavelength. The wavelength on FR4 PCB is 2e8/f (length in m, frequency in Hz).


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