I have 3 separate grounds in my project:
- AGND - Analog ground is very quiet, very small relatively smooth currents
- PGND - Power ground used for power bypass caps and power supply related circuitry is less quiet
- DGND - Dirty ground for digtal, led drivers, relays and things that cause horrible fast transient spikes and high current spikes
These grounds run over separate traces / wires back to a "star" on the power supply board.
Q: If I make a ground plane area that is DGND (the "dirty" ground), is that more or less likely to emit noise that could be picked up by surrounding circuitry as opposed to making the DGND circuitry regular traces and using another ground like PGND for the ground plane?
Generally we think of ground as being a low noise low impedance path. But if it's actually really noisy like a "dirty" ground that can see enough current to cause 100 mV spikes relative to a regular "quiet" ground, is that suitable for a ground plane or will putting noise into a big plane cause more harm than good?