Specifications

DP83848C

DP83848I

DP83848VYB, DP83848YB

www.ti.com

SNLS266E –MAY 2007–REVISED MARCH 2015

In order to ensure quality transmission when employing MLT-3 encoding, the compensation must be able

to adapt to various cable lengths and cable types depending on the installed environment. The selection of

long cable lengths for a given implementation, requires significant compensation which will over-

compensate for shorter, less attenuating lengths. Conversely, the selection of short or intermediate cable

lengths requiring less compensation will cause serious under-compensation for longer length cables. The

compensation or equalization must be adaptive to ensure proper conditioning of the received signal

independent of the cable length.

The DP83848VYB 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 6-8 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 6-7. EIA/TIA Attenuation vs. Frequency for 0, 50, 100, 130 and 150 Meters of CAT 5 Cable

6.5.1.2.2.2 Base Line Wander Compensation

Figure 6-8. 100BASE-TX BLW Event

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