Datasheet

BUS CABLE
SLOPE CONTROL
1
2
3
4 5
6
7
8
CANL
R
CANH
Vcc
Rs
GND
LBK
D
IOPF6
TMS320LF2407
10 kΩ
to
100 kΩ
0
5
10
15
20
25
0 4.7 6.8 10 15 22 33 47 68 100
Slope (V/us)
Slope Control Resistance - kΩ
SN65HVD233
SN65HVD234
SN65HVD235
SLLS557F – NOVEMBER 2002 – REVISED AUGUST 2008 .............................................................................................................................................. www.ti.com
The ISO-11898 Standard specifies a maximum bus length of 40 m and maximum stub length of 0.3 m with a
maximum of 30 nodes. However, with careful design, users can have longer cables, longer stub lengths, and
many more nodes to a bus. A large number of nodes requires a transceiver with high input impedance such as
the HVD233.
The standard specifies the interconnect to be a single twisted-pair cable (shielded or unshielded) with 120- Ω
characteristic impedance (Z
O
). Resistors equal to the characteristic impedance of the line terminate both ends of
the cable to prevent signal reflections. Unterminated drop-lines (stubs) connecting nodes to the bus should be
kept as short as possible to minimize signal reflections.
The rise and fall slope of the SN65HVD233, SN65HVD234, and SN65HVD235 driver output can be adjusted by
connecting a resistor from the Rs (pin 8) to ground (GND), or to a low-level input voltage as shown in Figure 30 .
The slope of the driver output signal is proportional to the pin's output current. This slope control is implemented
with an external resistor value of 10 k Ω to achieve a ≈ 15 V/ µ s slew rate, and up to 100 k Ω to achieve a ≈ 2.0 V/ µ s
slew rate as displayed in Figure 31 . Typical driver output waveforms with slope control are displayed in
Figure 32 .
Figure 30. Slope Control/Standby Connection to a DSP
Figure 31. HVD233 Driver Output Signal Slope vs Slope Control Resistance Value
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Product Folder Link(s): SN65HVD233 SN65HVD234 SN65HVD235