Correct Wiring of Electrically Isolated CAN Networks
6.2 Light Industrial Environment (
Single
Twisted Pair Cable)
6.2.1 General Rules
The following
general rules
for CAN wiring with single shielded
single
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 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 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 cables from disturbing sources. If this cannot be avoided, double shielded wires are
recommended.
Figure 5:
CAN wiring for light industrial environment
CAN-PCI104/200
Hardware Manual • Doc. No.: C.2046.21 / Rev. 1.1
Page 19 of 29
CAN GND
CAN_H
CAN_GND
n.c.
CAN_L
1
4
5
6
7
9
2
3
8
9
1
4
5
6
7
3
8
2
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.
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. = not connected
DSUB9 connector
(female or male)
pin designation
connector case
connector case
DSUB9 connector
(female or male)
pin designation
CAN wire with connectors
