Correct Wiring of Electrically Isolated CAN Networks
Page 20 of 31
Hardware Manual Doc.-Nr.: C.2035.21 / Rev. 2.2
CPCI-CAN/200
7.2.1 General Rules
NOTICE
esd only grants the compliance with directive 2014/30/EU, if the CAN wiring is carried out
with single shielded
double twisted
pair cables that match the requirements of
ISO 11898-2.
The following
general rules
for the CAN wiring with single shielded
double
twisted pair cable should
be followed:
1
A cable type with a wave impedance of about 120
Ω
±
10% with an adequate conductor cross-section
(
≥ 0.22 mm
²
) has to be used. The voltage drop over the wire has to be considered.
2
For heavy industrial environment use a four-wire CAN cable.
Connect
•
•
•
two twisted wires to the data signals (CAN_H, CAN_L) and
the other two twisted wires to the reference potential (CAN_GND) and
the cable shield to functional earth (FE) at least at one point.
3
The reference potential CAN_GND has to be connected to the functional earth (FE) at exactly
one
point.
4
A CAN bus line must not branch (exception: short cable stubs) and has to be terminated with the
characteristic impedance of the line (generally 120
Ω
±
10%) at both ends (between the signals CAN_L
and CAN_H and
not
to CAN_GND).
5
Keep cable stubs as short as possible (l < 0.3 m).
6
Select a working combination of bit rate and cable length.
7
Keep away CAN cables from disturbing sources. If this can not be avoided, double shielded cables are
recommended.
Figure 4:
CAN wiring for heavy industrial environment
7.2 Heavy Industrial Environment (Double Twisted Pair
Cable)
