DS92LV1023E Datasheet, PDF (11/13 Pages) National Semiconductor (TI) – 30-66 MHz 10 Bit Bus LVDS Serializer

Application Information
USING THE SERIALIZER AND DESERIALIZER CHIPSET
The Serializer and Deserializer chipset is an easy to use
transmitter and receiver pair that sends 10 bits of parallel
LVTTL data over a serial Bus LVDS link up to 660 Mbps. An
on-board PLL serializes the input data and embeds two clock
bits within the data stream. The Deserializer uses a separate
reference clock (REFCLK) and an onboard PLL to extract
the clock information from the incoming data stream and
then deserialize the data. The Deserializer monitors the
incoming clock information, determines lock status, and as-
serts the LOCK output high when loss of lock occurs.
POWER CONSIDERATIONS
An all CMOS design of the Serializer and Deserializer makes
them inherently low power devices. In addition, the constant
current source nature of the Bus LVDS outputs minimizes
the slope of the speed vs. I_CC curve of conventional CMOS
designs.
TRANSMITTING DATA
Once you power up the Serializer and Deserializer, they
must be phase locked to each other to transmit data. Phase
locking occurs when the Deserializer locks to incoming data
or when the Serializer sends patterns. The Serializer sends
SYNC patterns whenever the SYNC1 or SYNC2 inputs are
high. The LOCK output of the Deserializer remains high until
it has locked to the incoming data stream. Connecting the
LOCK output of the Deserializer to one of the SYNC inputs of
the Serializer will guarantee that enough SYNC patterns are
sent to achieve Deserializer lock.
The Deserializer can also lock to incoming data by simply
powering up the device and allowing the “random lock”
circuitry to find and lock to the data stream.
While the Deserializer LOCK output is low, data at the De-
serializer outputs (ROUT0-9) is valid, except for the specific
case of loss of lock during transmission which is further
discussed in the "Recovering from LOCK Loss" section be-
low.
HOT INSERTION
All the BLVDS devices are hot pluggable if you follow a few
rules. When inserting, ensure the Ground pin(s) makes con-
tact first, then the VCC pin(s), and then the I/O pins. When
removing, the I/O pins should be unplugged first, then the
VCC, then the Ground. Random lock hot insertion is illus-
trated in Figure 12.
PCB CONSIDERATIONS
The Bus LVDS Serializer and Deserializer should be placed
as close to the edge connector as possible. In multiple
Deserializer applications, the distance from the Deserializer
to the slot connector appears as a stub to the Serializer
driving the backplane traces. Longer stubs lower the imped-
ance of the bus, increase the load on the Serializer, and
lower the threshold margin at the Deserializers. Deserializer
devices should be placed much less than one inch from slot
connectors. Because transition times are very fast on the
Serializer Bus LVDS outputs, reducing stub lengths as much
as possible is the best method to ensure signal integrity.
TRANSMISSION MEDIA
The Serializer and Deserializer can also be used in point-to-
point configuration of a backplane, through a PCB trace, or
through twisted pair cable. In point-to-point configuration, the
transmission media need only be terminated at the receiver
end. Please note that in point-to-point configuration, the
potential of offsetting the ground levels of the Serializer vs.
the Deserializer must be considered. Also, Bus LVDS pro-
vides a +/− 1.2V common mode range at the receiver inputs.
20131817
FIGURE 12. Random Lock Hot Insertion
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