Are there any important points to consider, especially about noise, when more than one switching regulator is connected into the same ground reference, or is having a separate ground layer in the PCB good enough?
To summarize, are there any extra precautions to take while dealing with multiple switching regulators or designing them one by one when it comes to dealing with noise?
I have always used a "star" connection when dealing with multiple EMI sources but it is highly dependant on the circumstances of how you are using them. A separate ground layer is essential for best performance. If you have multiple layers or two-sided pcb, put the regulators on one side that the other circuits on the other side. You are asking a very tough question. Good luck.
The star connection is a good principle, mainly connected under the IC. But the problem is to detect and correct a lay-out error when it occurs. An oscilloscope does not work as it sees much more disturbance than the real circuit, by the mass current to the oscilloscope (ghost signals) . I used a transformer + resistor to see voltage level differences in the reference wire. Using a galvanic separated current measurement instead of shunts helps to reduce the disturbance, but also the gate current disturbes the mass. It is one of the more difficult arts in pwover electronics...
Have you read these slides? http://ecee.colorado.edu/~ecen5797/course_material/layout.pdf
Please take a look to the 35 slide (the common-mode choke).
Regards...
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