Target Condition: From Dream House to Drill Files
Connect the Dots: Proactive Controlled Impedance
Beyond Design: Radiation and Interference Coupling
Estimated reading time: Less than a minute
Bert's Practical Design Notes: Are Guard Traces Worth It?
By definition, a guard trace is a trace routed coplanar between an aggressor line and a victim line. There has always been an argument about whether to use guard traces in high-speed digital and mixed signal applications to reduce the noise coupled from an aggressor transmission line to a victim transmission line.
On one side of the debate, the argument is that the guard trace should be shorted to ground at regular intervals along its length using stitching vias spaced at 1/10 of a wavelength of the highest frequency component of the aggressor’s signal. By doing so, it is believed the guard trace will act as a shield between the aggressor and victim traces.
On the other side, merely separating the victim trace to at least three times the line width from the aggressor is good enough. The reasoning is that crosstalk falls off rapidly with increased spacing anyway, and by adding a guard trace, you will already have at least three times the trace separation to fit it in.Read the full column here.Editor's Note: This column originally appeared in the April 2013 issue of The PCB Design Magazine.
Share on:
More Columns from Bert's Practical Design Notes
Practical Modeling of High-Speed Backplane ChannelsObsessing over Conductor Surface Roughness: What’s the Effect on Dk?
The PDN Bandini Mountain and Other Things I Didn’t Know I Didn’t Know
Bert's Practical Design Notes: Accelerating the SI Learning Curve - Bogatin's SI Academy
Bert's Practical Design Notes: Perils of Lumped Via Modeling
Bert's Practical Design Notes: The "Stubinator" vs. Back-Drilling
Backplane High-Level Design: The Secret to Success
Bert's Practical Design Notes: Why Backplane Architecture is Crucial