LTC2274 datasheet(23/40 Pages) LINER

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LTC2274

2274f

APPLICATIONS INFORMATION

SERIALIZED DATA FRAME

Prior to serialization, the ADC data is encoded into the

8B/10B format, which is DC balanced, and run-length

limited. The receiver is required to lock onto the data

and recover the clock with the use of a PLL. The 8B/10B

format requires that the ADC data be broken up into 8-bit

blocks (octets), which is encoded into 10-bit code groups

applying the 8B/10B rules (refer to IEEE Std 802.3-2002

Part 3, for a complete 8B/10B description).

Figure 12 illustrates the generation of one complete 8B/10B

frame. The 8 most signiﬁcant bits of the ADC are assigned

to the ﬁrst half of the frame, and the remaining 8 bits

to the second half of the frame. Next, the two resulting

octets are optionally scrambled and encoded into their

corresponding 8B/10B code. Finally, the two 10-bit code

groups are serialized and transmitted beginning with Bit

0 of code group 1.

+–

AIN–

AIN+

S/H

AMP

DIGITAL

SUMMATION

8b10b

ENCODER

MULTIBIT DEEP

PSEUDO-RANDOM

NUMBER

GENERATOR

16-BIT

PIPELINED

ADC CORE

PRECISION

DAC

CLOCK/DUTY

CYCLE

CONTROL

ENC

DITHER ENABLE

HIGH = DITHER ON

LOW = DITHER OFF

DITH

ENC

ANALOG

INPUT

2274 F11

LTC2274

CMLOUT+

CMLOUT–

SERIALIZER

Figure 11. Functional Equivalent Block Diagram of Internal Dither Circuit

Figure 12. Evolution of One Transmitted Frame (Compare to IEEE Std 802.3-2002 Part 3, Figure 36-3)

BIT

FIRST OCTET

ADC OUTPUT WORD

MSB

LSB

OCTET

ASSIGNMENT

OPTIONAL

SCRAMBLER

8B/10B

ENCODER

BIT

FIRST SCRAMBLED OCTET

8B/10B CODE GROUP 1

BIT 0 OF CODE GROUP 1 IS TRANSMITTED FIRST

BIT

SECOND OCTET

BIT

SECOND SCRAMBLED OCTET

8B/10B CODE GROUP 2

ONE FRAME

SERIAL OUT

2274 F12

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