Group,
Can anyone advice on any guide for checking/qualifying second source
component, such as crystal, oscillator & ferrite bead, mounted on
product is still meeting the emission limits?
We are manufacturer of pheripherals cards. Some card has crystal and/or
oscillator for digital circuitry. Ferrite bead are used too.
As these component will affect the final product EMI level, therefore
some qualification/guide in terms of EMI must be considered when
qualifying second source component.
These components are used in lots of product that we made, it would be
costly to perform scan for every model.
Every product are tested and pass EMI with initial source components.
Can we just made a comparison of the specification of the first source
compnent with this second source?
If yes, what are the crucial specs/information that must meet the first
source component?
For crystal/oscillator, beside the Frequency stability & tolerance
specs, what other item is crucial.
For Ferrite bead, impedance curve, what other item is crucial.
If happens that some specs are slightly out, e.g. 2nd source crystal are
having 5PPM more than initla source crystal,
Can we make use of the product passing margin, say 3dB, and do some
calculation to confidently say that the second source component on the
card is still EMI compliance. Likewise for oscillator and ferrite bead.
If yes, could you advice on an example of such calculation.
Many thanks in advance for the replies.
Regards
Koh
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