Civil Engineering Reference
In-Depth Information
Fig. 2.24
Separated grounding of communication and application
GND shifts are critical because they induce common-mode currents which lead
to worse EMC behaviour of the network and, in the case of huge GND shifts, the
information exchange itself is endangered by wrong bit decoding.
One solution to avoid GND shifts, caused by the current consumption of the
application, is to separate the GND line for the CAN communication and for the
application as well as a galvanic isolation between the CAN communication and the
application. Regarding the supply of the CAN communication parts, the galvanic
isolation can be realized by direct current (DC)/DC converter; the galvanic isolation
of the logic signals RxD and TxD can be realized by optocouplers. EMC behaviour
and interference immunity are enhanced by the isolation of the CAN physical layer.
The explained concept is depicted in Fig.
2.24
.
2.2.3
Interactions of Components and Analytic Signal Integrity
Inspections
An elementary problem at signal integrity valuations is the interactions of influ-
ences of different components on the overall behaviour of the system. That only
the sum of all influences can be measured is problematic. A systematic approach is
needed to identify and localize particular influences and to be able to evaluate these
influences.
Sections 2.2.1 and 2.2.2 describe the influences of network components as well
as those of the network architecture. The characteristics were analysed isolated
from influences of other network component or influencing parts.
This section, however, describes, taking examples from praxis, how the different
components interact with each other and how these interactions result in changes
of the signal integrity of the overall system. Furthermore, analytic procedures are
introduced to allow a specific consideration of the signal quality.
