to the +3.3V logic level. Figure 5 shows the circuit that
interfaces the crossbar switches to the LIN bus.
Waking Up the LIN Bus Driver
At power-up, the MAX9132/MAX9134/MAX9135 leave
NSLP low, keeping the LIN bus driver in sleep mode.
When the LIN driver receives a wake-up signal (Figure
6) from the LIN bus, the driver pulls RXD low. When the
MAX9132/MAX9134/MAX9135 detect a falling edge on
RXD, the device pulls NSLP high waking up the LIN dri-
ver. The MAX9132/MAX9134/MAX9135 then enable the
TXD pin.
Putting the LIN Bus Driver into Sleep Mode
There are two conditions under which the MAX9132/
MAX9134/MAX9135 put the LIN driver to sleep: line
activity timeout and receiving a sleep command. The
first condition arises if there is inactivity on the LIN bus
for more than 3s. The second condition requires send-
ing the data 0x00 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF
using the identifier 0x3C to the device. If any of the two
conditions happen, the device disables TXD and drives
NSLP low. This puts the LIN driver into sleep mode.
Multiple MAX9132/MAX9134/MAX9135 for
Port Expansion
The MAX9132/MAX9134/MAX9135 high-impedance
outputs allow the attachment of several parts in parallel.
Figure 7 shows example connection schemes to realize
larger crossbar connections.
LVDS Output Preemphasis
The MAX9132/MAX9134/MAX9135 feature a preem-
phasis mode where extra current is added to the output
and causes the amplitude to increase by 50% at the
transition point. Preemphasis helps to get a faster tran-
sition, better eye diagram, and improved signal integri-
ty (see the
Typical Operating Characteristics
). During
data transition, the switch injects additional current for
a short period, typically 400ps. Leave PD open or apply
a midlevel voltage (V
DD
/2) to enable preemphasis on
all LVDS outputs. Set PD high to set preemphasis
through the I
2
C or LIN interfaces. Preemphasis in this
mode is initially not on.
Power-Down
Set PD low to enable power-down mode. The registers
retain their values and the device resumes operation
from the same mode upon power-up.
MAX9132/MAX9134/MAX9135
Programmable, High-Speed, Multiple
Input/Output LVDS Crossbar Switches
______________________________________________________________________________________ 15
(22 Seiten)
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