USB traces

Former Member over 11 years ago

This is not an Eagle-specific question, but I need to do a short run

of traces between two USB connectors on a board, connecting a USB host

with a USB slave. I have never laid out USB signals before and I am a

little nervous about how to do it. Must I treat the data lines as RF

transmission lines? What trace width and spacing should I use? Can I

use vias? What trace thickness should I use? The traces joining the

two recepticals are only going to be about 2 inches long. How

critical is USB layout anyway?

Robert Scott

Ypsilanti, Michigan

amigabill over 11 years ago

If you're USB2 speeds, then soem care should be taken. I don't know
about USB1 speeds.

As it sounds like you are doing a connector/board/connector thing, I
will assume you are not going to be within the rise time distance that
lets you ignore impedance matching, and that you will have to pay
attention to that.

Some USB2 layout guides I found on the google:
http://www.ti.com/lit/an/spraar7/spraar7.pdf
http://www.usb.org/developers/docs/hs_usb_pdg_r1_0.pdf
http://www.atmel.com/Images/doc7633.pdf

These are likely to talk about driver to connector type things more than
connector direct to connector things. Figure out your target impedance
and work to that. Figure out what trace width/space is easy to
manufacturer from your board peeps, and choose a width/space/height from
plane combination to suite the impedance needs.

billt

Robert Scott wrote:
This is not an Eagle-specific question, but I need to do a short run
of traces between two USB connectors on a board, connecting a USB host
with a USB slave. I have never laid out USB signals before and I am a
little nervous about how to do it. Must I treat the data lines as RF
transmission lines? What trace width and spacing should I use? Can I
use vias? What trace thickness should I use? The traces joining the
two recepticals are only going to be about 2 inches long. How
critical is USB layout anyway?

Robert Scott
Ypsilanti, Michigan
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Former Member over 11 years ago in reply to amigabill

On Tue, 06 Mar 2012 14:26:42 -0500, Bill Toner <amigabill@gmail.com>
wrote:

>If you're USB2 speeds, then soem care should be taken. I don't know
>about USB1 speeds.
>As it sounds like you are doing a connector/board/connector thing, I
>will assume you are not going to be within the rise time distance that
>lets you ignore impedance matching, and that you will have to pay
>attention to that.
>Some USB2 layout guides I found on the google:
>http://www.ti.com/lit/an/spraar7/spraar7.pdf
>http://www.usb.org/developers/docs/hs_usb_pdg_r1_0.pdf
>http://www.atmel.com/Images/doc7633.pdf

These documents are exactly what I needed. Thanks for the pointers.

Robert Scott
Ypsilanti, Michigan
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