Hi
When laying out a pcb/pwb, if a signal source needs to be ac coupled to a
receiver, is it best to:
1) put the cap nearest the source,
2) in the middle, or
3) nearest the receiver?
Noise considerations would suggest that tracking to the first active
node of the reciever be minimized. As a coupling capacitor is intended
to look like a short at the frequencies communicated, it simply
increases the effective pick-up area of the tracking wherever it is
situated.
Singlre-fault abnormal implications would suggest that the capacitor
be closest to the node that would be most physically damaged by a
single fault to ground, or adjacent tracking. This could be either
node, but the transmission side usually has greater potential circuit
component loss under the abnormal fault, as it is configured to
deliver power. This is an issue of recoverability, repairability.
Series resistor tracking can have a larger affect on nodes subjected
to external noise sources than series coupling caps.
RL