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Grundlagen FlexRay BasicsV 1.1 16
Terminated end of a cable
R T = 80…110 Ω
Figure 2.5 Termination with a resistor [FREPLS06]
A ECU with termination is marked by a filled black square.
A better way of termination is shown in Figure 2.6. The resistor R T is replaced by two
identical resistors R TA and R TB . In between these two resistors, a 20 MHz RC filter is placed.
R TA , R TB = 40...55 Ω
R 1 < 10 Ω
C 1 = 4700 pF
Figure 2.6 Termination with RC filter [FREPLA06]
The properties of the termination and the electromagnetic compliance can be further
increased, by using a Common Mode Choke. The configuration is shown in Figure 2.7. The
stray inductivity L stray should be low.
R Line ≤ 1 Ω
L ≥ 100 µH
L stray < 1µH
Figure 2.7 Termination with RCL filter[FREPLA06]
Not every node of the bus can be equipped with a terminating resistor, because the resistance
of the whole bus would be too low. At nodes without terminations (see Figure 2.8), the Bus
Driver is directly connected to the bus.
Bäurle 12.10.2012