Since the cable conducts noise, EMI filters are installed in the cable
connections. Generally, the BLM Series (Chip Ferrite Bead), and a capacitor
type EMI filter such as the NFM21C Series (Chip Solid "EMIFIL®"),
are used in combination. To get the maximum effects from this capacitor-type
EMI filter, it is important to minimize the impedance at high frequencies
between the filter's GND and the metal case.
The number of points where the PCB's GND and metal case are screwed together
is increased. An additional finger is attached to the PCB's GND to increase
the number of connections between the PCB and metal case. |
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