I am trying to select common mode chokes for a board that I am designing. The point of doubt is common mode and differential mode noise filtering and the parameters/values of the components selected.
Now, the system consist of the following - battery connected to my PCB via wires(Vcc and GND) of 20V or so, Buck regulator and the rest of the system.
Now, having long wires from the batteries I understand that there can be common mode noise that can creep into my system. So I am having a common mode choke (XFMR1). L1 and C1 will filter out differential noise.
I understand how these 3 work. Now, what purpose does C1 serve ?
Suppose my buck regulator supplies 4Amps,this would mean I will have to select a common mode choke greater than 4Amps rating,right ? Now, the common mode choke has the property of having a high impedance at specific frequencies. What frequency will my choke be of ? As it is coming from the battery and since the battery is connected to many other boards, it is difficult to zero in on a certain frequency,right ? How do I start about it please ?