Type: Answers
Area: Component


Last Modified: June 16, 2016

What I/O standard should I use when driving signals over long lengths of cable?

Description

Generally LVDS is a good choice for long lengths in noisy environments.  The advantage is the differential nature of the standard helps to maintain the signal integrity as well as keep signals coupled to their respective opposite polarity instead of coupling to other signals in the cable.  However, that would only be beneficial if the cable is manufactured for differential signaling, such as having twisted pairs for specific channels.  If the cable does not have twisted pairs, or other methods to ensure the positive and negative legs of each LVDS pair are coupled, then you lose some of the LVDS advantages.

You can refer to Board Design Guidelines for LVDS Systems (PDF) for further information.

You can also try using a single ended standard using a high drive strength, but then you will not have the benefit of your cable being as immune to noise as differential signaling would provide

To verify functionality and maximum cable length, you should simulate the interface using Altera® IBIS models.  You will also need an IBIS model for the cable you intend to use.  This is the best way to ensure you make the best choice for your system.