Cable Selection - ICP DAS USA I-7530 User Manual

2.7

Cable selection

The CAN bus is a Balanced (differential) 2-wire interface running over
either a Shielded Twisted Pair (STP), Un-shielded Twisted Pair (UTP), or
Ribbon cable. The CAN-L and CAN-H Wire start on one end of the total
CAN network that a terminator of 120 Ohm is connected between CAN-L
and CAN-H. The cable is connected from CAN node to CAN node,
normally without or with short T connections. On the other end of the
cable again a 120Ω(Ohm) terminator resistor is connected between the
CAN lines. How to decide a cable type, cable length, and terminator
depends on the baud rate in the CAN BUS network, please refer to the
following table 4.
Figure 9: Un-shielded Twisted Pair (UTP)
Bus speed
50k bit/s at 1000m
100k bit/s at 500m
500k bit/s at 100m
1000k bit/s at 40m
Note: The AWG means a standard method used to measure wire. The
numbering system works backwards from what people would think, the
thicker (heavier) the wire, the lower the number. For example: a 24AWG
wire is thicker/heavier than a 26AWG wire.
I-7530 RS-232/CAN Converter User's Manual (Version 2.0, Sep/2007) ------------- 12
Table 4: Cable selection
Cable type
resistance/m
0.75~0.8mm2
18AWG
0.5~0.6 mm2
20AWG
0.34~0.6mm2
22AWG,
20AWG
0.25~0.34mm2
23AWG,
22AWG
Cable
Terminator Bus Length
150~300
70 mOhm
Ohm
150~300
< 60 mOhm
Ohm
< 40 mOhm 127 Ohm
< 40 mOhm 124 Ohm
600~1000m
300~600m
40~300m
0~40m