PCB Design
Grounding and Return Paths in Mixed-Signal PCBs
A ground label does not make every point electrically identical at all frequencies.
A ground label does not make every point electrically identical at all frequencies. Review current loops and component guidance when laying out mixed-signal boards.
Trace the complete current loop
For each sensitive input and fast switching signal, consider the outgoing and return paths together. Keep noisy power loops compact and separate their placement from small sensor signals. Do not route critical signals across reference-plane gaps without a deliberate return strategy.
Follow device-specific guidance
Review converter, amplifier and interface datasheets for grounding and decoupling recommendations. Analogue and digital pin names do not automatically require separate planes. Galvanic isolation has different constraints and must retain its intended barrier and spacing.
Measure noise under activity
Test sensor readings while radios transmit, relays switch and processors communicate. Use appropriate probing to avoid creating misleading loop pickup. Compare noise against the application error budget and revise placement or return routing based on observed coupling.
FAQ
Should analogue and digital ground always be split?
No. The right arrangement depends on device guidance, current paths and isolation requirements.
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