2.2.3 Printed circuit protection
The e.m. interference problemes born already from the printed circuit level where the logical circuits involved is diffused and incidental digital signals always faster and therefore of harmonic contain always wider.
The big problemes that rise to the printed circuit level born from this reason:
- the signals current flow along the feeding pistes closing through the feeder; these pistes that are assimilated to the inductances for the r.f., acting like the radiant elements;
- the currents of different devices (integrated circuit) follow all together a piece of piste causing a d.d.p. to its extremes; this piste piece becomes an impedance to more circuits.
How to intervene on the printed circuit
- Keep the logical signals pistes shorter as it can, can be necessary reunite and enclose them removed from the printed circuit and far away from the I/O points of the same circuit.
- Involve the clocks with the rise/decline times as slower as possible;
- Involve the "multilevel" printed circuits to have the maximum wide and reduce the pairing area with the e.m. wave.
- Separate the different feeding lines and the ground (return) to the different circuits considered critical.
- Alternate the conductors' signal and the ground in the cable (flat cable job) and in the connector;
- Involve the signal's connectors filtrated ;
- Involve the rings of hurt .
See also: PCB
Espanol
French
Italian
