Correctly Wiring Electrically Isolated CAN Networks
6.3 Electrical Grounding
●
CAN_GND has to be connected between the CAN devices, because esd CAN devices are
electrically isolated from each other!
●
CAN_GND has to be connected to the earth potential (FE) at
exactly one
point of the
network!
●
Each CAN interface without electrically isolated interface acts as an earthing point. For this
reason do not connect more than one CAN device without electrically isolated CAN
interface!
●
Earthing can e.g. be made at a connector/T-connector.
6.4 Bus Length
●
Optical couplers are delaying the CAN signals. esd modules typically reach a wire length of
37 m at 1 Mbit/s within a closed net without impedance disturbances like e.g. cable stubs
>> 0.3 m.
Bit rate
[Kbits/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
800
666.6
500
333.3
250
166
125
100
66.6
50
33.3
20
12.5
10
37
59
80
130
180
270
420
570
710
1000
1400
2000
3600
5400
7300
25
50
-
100
-
250
-
500
650
-
1000
-
2500
-
5000
Table 6:
Recommended cable lengths at typical bit rates (with esd-CAN interfaces)
Note:
Please note the recommendations according to ISO 11898 for the selection of the cross
section of the wire depending of the wire length.
CAN-USB/2
Hardware Manual • Doc. No.: C.2066.21 / Rev. 1.4
Page 19 of 25
