LTC2274 Linear Technology, LTC2274 Datasheet - Page 16

• Manufacturer Part Number: LTC2274
• Description: 105Msps Serial Output ADC
• Manufacturer: Linear Technology

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DEFINITIONS
LTC2274
a D16.2 will be transmitted after the comma, otherwise
a D5.6 will be transmitted. The result is that the ending
disparity of an idle ordered set will always be negative.
Initial Frame Synchronization
The process of communicating frame synchronization
information to the receiver upon the request of the receiver.
For JESD204 compliance, K28.5 commas are transmitted
as the preamble. Once the preamble has been detected
the receiver terminates the synchronization request, and
the preamble transmission continues until the end of the
frame. The receiver designates the fi rst normal data word
after the preamble to be the start of the data frame.
Octet
The 8-bit input to an 8B/10B encoder, or the 8-bit output
from an 8B/10B decoder.
Run-Length Limited (RLL)
The act of limiting the number of consecutive 1’s or 0’s
in a data stream by encoding the data prior to serial
transmission.
This process guarantees that there will be an adequate
number of transitions in the serial data for the receiver
to lock onto with a phase-locked loop and recover the
high-speed clock.
Running Disparity
In order to maintain DC balance there are two possible
8B/10B output code-groups for each input octet. The
16
running disparity is calculated to determine which of the
two code-groups should be transmitted to maintain DC
balance.
The disparity of a code-group is analyzed in two segments
called sub-blocks. Sub-block1 consists of the fi rst six bits
of a code-group and sub-block2 consists of the last four
bits of a code-group. When a sub-block is more heavily
weighted with 1’s the running disparity is positive, and when
it is more heavily weighted with 0’s the running disparity
is negative. When the number of 1’s and 0’s are equal in a
sub-block, the running disparity remains unchanged.
The polarity of the current running disparity determines
which code-group should be transmitted to maintain DC
balance. For a complete description of disparity rules, refer
to IEEE Std 802.3-2002 part3, Clause 36.2.4.4.
Pseudo Random Bit Sequence (PRBS)
A data sequence having a random nature over a fi nite
interval. The most commonly used PRBS test patterns
may be described by a polynomial in the form of 1 + x
x
bits, where n indicates the order of the PRBS polynomial
and m plays a role in maximizing the length of the random
sequence.
Scrambler
A logic block that applies a pseudo random bit sequence
to the input octets to minimize the tonal content of the
high-speed serial bit stream.
n
and have a random nature for the length of up to 2
n
m
2274f
– 1
+