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EMC good practices

Discussion in 'General Electronics Discussion' started by Rajinder, Feb 6, 2018.

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  1. Rajinder


    Jan 30, 2016
    I was wondering if someone could help me with the following EMC and PCB layout questions:

    1. Why is it good to have a separate layer dedicated to the GND? Is it because it is a low inductance/resistance path to ground? i.e. less voltage spikes?
    2. Are track lines meant to be short as possible because the longer the track the more it radiates as a antenna?
    3. If I had a 30mm track, what would I need to change for a 1MHz square wave compared to a 5GHz square wave on the same length of track? What modifications would I need to make?
    4. I am not sure what ground current loops are and how to reduce the effects of these.
    5. When choosing a decoupling capacitor say for example a 100nF on a IC (between VCC and 0V) close to the IC pins. Do I use Xc = 1/(2*PI*F*C) as the formula? For the frequency (is that the frequency of the signal I am looking to reduce?) Also should I aim for a value of XC to be as low as possible but not 0, as 0 would be a short between VCC and 0V?
    6. Why is it a good idea to have the VCC and GND layers (on a 4 layer PCB), back to back?

    Thanks in advance
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    People have answered this question so many times on the internet.
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