CAN-8x23 user’s manual (Revision 3.20, Ma r/08/2012) ------
12
2.3 Wire Connection
In order to minimize the reflection on the CAN bus line, the CAN bus line
has to be terminated at both ends by two terminal resistances as shown in the
following. According to the ISO 11898-2 spec, each terminal resistance is
120Ω (or other between 108Ω~132Ω). The length related resistance has to
reach
70mΩ/m. At this circumstance, users would better check the resistances
of the CAN bus before installing a new CAN network.
12
0
Ω
12
0
Ω
CAN_H
CAN_L
Device N
Device 2
Device 1
. . .
Moreover, to minimize the voltage drop, value of the terminal resistance
must be higher than the one defined in the ISO 11898-2. The following table is
for users
’ reference.
Bus Length
(meter)
Bus Cable Parameters
Terminal
Resistance
(Ω)
Length Related
Resistance
(mΩ/m)
Cross Section
(Type)
0~40
70
0.25(23AWG)~
0.34mm
2
(22AWG)
124 (0.1%)
40~300
< 60
0.34(22AWG)~
0.6mm
2
(20AWG)
127 (0.1%)
300~600
< 40
0.5~0.6mm
2
(20AWG)
150~300
600~1K
< 20
0.75~0.8mm
2
(18AWG)
150~300
In the CAN-8x23,
the 120Ω terminal resistance is supplied as a standard
accessory. About enable/disable the
120Ω terminal resistance jumps, please
refer to section
2.5
“Terminal Resistor Jumper and Initial Switch”
.