Specifications

DP83848Q-Q1
SNLS341C –MARCH 2011–REVISED MARCH 2015 www.ti.com
The DP83848Q-Q1 uses an extremely robust equalization scheme referred as ‘Digital Adaptive
Equalization.’
The Digital Equalizer removes ISI (inter symbol interference) from the receive data stream by continuously
adapting to provide a filter with the inverse frequency response of the channel. Equalization is combined
with an adaptive gain control stage. This enables the receive 'eye pattern' to be opened sufficiently to
allow very reliable data recovery.
The curves given in Figure 5-8 illustrate attenuation at certain frequencies for given cable lengths. This is
derived from the worst case frequency vs. attenuation figures as specified in the EIA/TIA Bulletin TSB-36.
These curves indicate the significant variations in signal attenuation that must be compensated for by the
receive adaptive equalization circuit.
Figure 5-7. EIA/TIA Attenuation vs. Frequency for 0, 50, 100, 130 & 150 Meters of CAT 5 Cable
5.5.1.2.2.2 Base Line Wander Compensation
Figure 5-8. 100BASE-TX BLW Event
The DP83848Q-Q1 is completely ANSI TP-PMD compliant and includes Base Line Wander (BLW)
compensation. The BLW compensation block can successfully recover the TP-PMD defined “killer”
pattern.
BLW can generally be defined as the change in the average DC content, relatively short period over time,
of an AC coupled digital transmission over a given transmission medium. (that is, copper wire).
BLW results from the interaction between the low frequency components of a transmitted bit stream and
the frequency response of the AC coupling component(s) within the transmission system. If the low
frequency content of the digital bit stream goes below the low frequency pole of the AC coupling
transformers then the droop characteristics of the transformers will dominate resulting in potentially
serious BLW.
40 Detailed Description Copyright © 2011–2015, Texas Instruments Incorporated
Submit Documentation Feedback
Product Folder Links: DP83848Q-Q1