Clock traces and GND layout issues

[neutrino]

Clock traces and GND

In general, clock/high speed traces on PCB, are made in microstrip and stripline topology. Sometimes i find speed traces with GND plane very close on same layer (near traces), sometimes far away. Why ?

Regards

 

[cyberrat]

Clock traces and GND

As a shield perhaps.

 

[dmd4raj]

Re: Clock traces and GND

Mostly the ground signal will guard the High speed /Clock traces,it will be placed close to the signals to protect the traces being caught to EMI interferences. It is also recommended to pour the Cu shapes around the clock Oscillator for Better EMI Protection


Regards
Rajan.K

 

[lhademmor]

Re: Clock traces and GND

Far away not to overload the driver with a low impedance in the traces.
Close to (as sayed) as guidance.

In general pcb routing, one should look at how much crosstalk is acceptable, and by that see if gnd is needed near by the trace. In many cases clock are diff pairs, and bad gnd near the trace can cost more pain, than no gnd at all.