Longer USB3.0 cables with U3 HDD Dock


#1

I have the U3 USB3.0 HDD dock and so far it’s working great. My question is a bit technical but … has Plugable done any performance testing with USB3.0 cables longer than the one supplied? Will a 6-foot USB3.0 cable likely allow data transfer rates similar to the factory cable? Also, does the U3 incorporate a “redriver” circuit in its design to allow use with longer cables in “noisy” environments where signal integrity can be an issue? Example redriver here:

http://www.eetimes.com/design/industr…


#2

Thanks for posting with the great info and question.

USB 3.0 cables are definitely a difficult issue, because of how the high data rates stress everything. We are still finding USB 3.0 cable quality to vary greatly.

Because of this, USB 3.0’s max specified cable length (3m) is shorter than USB 2.0 (5m). But it’s actually worse than that - our experience is limiting to 1 meter length is the practical limit right now for high reliability from mainstream sources. We expect that’ll improve over time, especially if usb.org implements a tight testing scheme.

The eetimes article was interesting. There are no redrivers in our USB 3.0 products (beyond the core USB 3.0 IC). EETimes lets vendors write articles to sell their products (Pericom is selling their redriver solution through the article - which is fine, because otherwise an article like that might never get written). So I don’t know how to judge the value of the redrivers they’re selling, but we’ll be on the look out for those kinds of opportunities with our designs.

So we recommend staying at 1m USB 3.0 cable length or so, if at all possible. But we’re hopeful that guidance will change as USB 3.0 matures.

Thanks again!
Bernie


#3

Thanks for the straight dope Bernie. This is why I puchased from Plugable, I think your tech support is better than most.

I’m an EE and have designed DVI/TDMS products in the past. The DVI bitrate on the twisted pairs is similar to USB3.0, so I know how tough it can be to keep your transitions within the required eye pattern.


#4