Wiring Notes
CPCI-405
Hardware-Manual • Doc.-No.: I.2306.21 / Rev. 3.5
Page 51 of 57
6.4 Electrical Grounding
For CAN devices with electrical isolation the CAN_GND must be connected between the CAN
devices.
CAN_GND should be connected to the earth potential (FE) at exactly one point of the network.
Each CAN interface with electrical connection to earth potential acts as grounding point.
For this reason it is recommended not to connect more than one CAN device with electrical
connection to earth potential.
Grounding can be made e.g. at a connector (e.g. order no. C.1302.01 or C.1301.01)
6.5 Bus Length
Bit-Rate
[kBit/s]
Typical values of reachable
wire length with esd
interface l
max
[m]
CiA recommendations
(07/95) for reachable wire
lengths l
min
[m]
1000
37
25
800
59
50
666 6
.
80
-
500
130
100
333 3
.
180
-
250
270
250
166
420
-
125
570
500
100
710
650
83 3
.
850
-
66 6
.
1000
-
50
1400
1000
33 3
.
2000
-
20
3600
2500
12.5
5400
-
10
7300
5000
Table 2: Recommended cable lengths at typical bit rates (with esd-CAN interfaces)
Optical couplers are delaying the CAN signals. esd modules typically reach a wire length of
37 m at 1 Mbit/s within a proper terminated CAN network without impedance disturbances like
e.g. caused by cable stubs > 0.3 m.
Note:
Please note the recommendations of ISO 11898 regarding to the configuration of the
conductor cross section in dependance of the cable length.