Correctly Wiring Electrically Isolated CAN Networks
6. Correctly Wiring Electrically Isolated CAN Networks
For the CAN wiring all applicable rules and regulations (EC, DIN), e.g. regarding electromagnetic
compatibility, security distances, cable cross-section or material, have to be met.
6.1 Light Industrial Environment (
Single
Twisted Pair Cable)
6.1.1 General Rules
Note:
esd grants the EC Conformity of the product, if the CAN wiring is carried out with at
least single shielded
single
twisted pair cables that match the requirements of ISO
118982-2. Single shielded
double
twisted pair cable wiring as described in chapter 6.2.
ensures the EC Conformity as well.
The following
general rules
for CAN wiring with single shielded
single
twisted pair cable must be
followed:
1
A cable type with a wave impedance of about 120 Ω ±10% with an adequate wire cross-section
(0.22 mm²) has to be used. The voltage drop over the wire has to be considered!
2
For light industrial environment use at least a two-wire CAN cable. Connect
•
•
the two twisted wires to the data signals (CAN_H, CAN_L) and
the cable shield to the reference potential (CAN_GND)!
3
The reference potential CAN_GND has to be connected to the functional earth (FE) at exactly
one
point.
4
A CAN net 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
at 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 cables from disturbing sources. If this cannot be avoided, double shielded wires are
recommended.
Figure. 4:
CAN wiring for light industrial environment
CAN-USB/2
Hardware Manual • Doc. No.: C.2066.21 / Rev. 1.4
Page 15 of 25
CAN GND
CAN_H
CAN_GND
n.c.
n.c.
n.c.
n.c.
CAN_L
1
4
5
6
7
9
2
3
8
9
1
4
5
6
7
3
8
2
earth (FE)
CAN_L
CAN_H
CAN_GND
Single shielded
twisted pair cable
(two-wire cable,
1x 2x 0.22mm²)
CAN_GND
(at wire shield)
Wire Layout
Signal assignment of single shielded twisted pair cable
with earth and termination
n.c.
n.c.
n.c.
n.c.
n.c.
n.c.
n.c.
n.c.
n.c.
n.c.
n.c.
n.c.
n.c.
n.c.
n.c. = not connected
DSUB9 connector
(female or male)
pin designation
connector case
connector case
DSUB9 connector
(female or male)
pin designation
CAN wire with connectors
