I am trying to understand concepts in common mode voltage and EMI due to it. Now, I understand that differential mode is the difference between the P and N wires/signals. The common mode is the - (P+N)/2.This is w.r.t ground. Now, the common mode currents are induced due to noise generated via long wires that are connected to PCBs(that carried signals or power).
Now, the common mode current is dumped into the ground and thus making my ground noisy. Now my doubts are the following -
- Common mode noise is generated in power lines(Vcc and GND) or in differential signal lines(RS422,485) or in both ?
- If common mode noise is dumped into my ground and if I have a common ground my whole ground will be corrupted,right?
- How should the common mode ground be coupled to my main GND plane ?
Also, I have long wires bringingin in Vcc,GND,and RS422 signals. So, where all should I put common mode chokes to filter common mode noise ?