Every signal sent down a trace must find its way back to the source ground, and it will always take the path of least impedance. At low frequencies, this is the path of least resistance, but at high frequencies, the return current flows directly underneath the signal trace to minimize loop area and inductance. Poorly designed return paths cause electromagnetic interference, ground bounce, and signal degradation.
You routed the high-speed clock right over a gap in the ground plane, completely destroying its return path.
High-frequency return currents mirror the signal trace. If you split the ground plane under a fast signal, the return current has to loop around the gap, creating a massive EMI-radiating loop antenna.
Also heard as
- ground return
Related terms
PCB
A laminated board holding and connecting electronic components using conductive traces.
Layout
The physical arrangement of components and traces on a chip or circuit board.
Floating ground
A zero-volt reference point in a circuit that is intentionally isolated from earth ground.
EMI
An external memory interface connects a microcontroller or processor to off-chip memory.