AC101LKQT Broadcom, AC101LKQT Datasheet - Page 12

• Manufacturer Part Number: AC101LKQT
• Manufacturer: Broadcom

Specifications of AC101LKQT

• Number Of Receivers: 1
• Data Rate: 10/100Mbps
• Package Type: TQFP
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 48
• Operating Temperature (max): 85C
• Operating Temperature (min): -40C
• Lead Free Status / Rohs Status: Not Compliant

AC101L
Preliminary Data Sheet
03/10/03
TX_CLK. This provides a continuously running RX_CLK. At the PCS interface, the 5-bit data RXD[4:0] is synchronized to
the 25 MHz RX_CLK.
B
W
C
ASELINE
ANDER
ORRECTION
A 100BASE-TX data stream is not always DC balanced. Because the receive signal must pass through a transformer, the
DC offset of the differential receive input can wander. This effect, known as baseline wander, can greatly reduce the noise
immunity of the receiver. The 100BASE-TX PHY automatically compensates for baseline wander by removing the DC offset
from the input signal, and thereby significantly reduces the chance of a receive symbol error.
The baseline wander circuit is not required in 100BASE-FX PHY operation.
M
-
T
ULTI
MODE
RANSMITTER
The multi-mode transmitter transmits MLT3 coded symbols in 100BASE-TX mode, and NRZI coded symbols in
100BASE-FX mode. It utilizes a current drive output, which is well balanced and produces very low noise transmit signals.
PECL voltage levels are produced with resistive terminations in 100BASE-FX mode.
The serialized data bypasses the scrambler and 4B/5B encoder in FX mode. The output data is NRZI PECL signals. The
PECL level signals are used to drive the fiber-optic transmitter.
S
C
S
/D
TREAM
IPHER
CRAMBLER
ESCRAMBLER
In 100BASE-TX mode, the transmit data stream is scrambled to reduce radiated emissions on the twisted-pair cable. The
data is scrambled by exclusive ORing the NRZ signal with the output of an 11-bit wide Linear Feedback Shift register (LFSR),
which produces a 2047 bit nonrepeating sequence. The scrambler reduces peak emission by randomly spreading the signal
energy over the transmit frequency range and eliminating peaks at certain frequencies.
The receiver descrambles the incoming data stream by exclusive ORing it with the same sequence generated at the
transmitter. The descrambler detects the state of the transmit LFSR by looking for a sequence representing consecutive idle
codes. The descrambler locks to the scrambler state after detecting a sufficient number of consecutive idle code group.
The receiver does not attempt to decode the data stream unless the descrambler is locked. When locked, the descrambler
continuously monitors the data stream to make sure that it has not lost synchronization.
The receive data stream is expected to contain inter-packet idle periods. If the descrambler does not detect enough idle code
within 724 µs, it becomes unlocked and the receive decoder is disabled. The descrambler is always forced into the unlock
state when a link failure condition is detected.
Stream cipher descrambler is not used in the 100BASE-FX mode.
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Document
AC101L-DS05-R