VT6103 datasheet(29/46 Pages) VIA

29 / 46 page

VT6103 - Fast Ethernet 10 / 100 PHY / Transceiver

Revision 1.1 April 15, 2002

-23-

Functional Description

Technologies, Inc.

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Twisted Pair Transmitter

Transmitter - 100 Mbps

The transmitter consists of an MLT-3 encoder, waveform

generator and line driver. The MLT-3 encoder converts the

NRZ data from the scrambler into a three level MLT-3 code.

MLT-3 coding uses three levels, converts 1's to transitions

between the three levels, and converts 0's to no transitions or

changes in level. The purpose of the waveform generator is to

shape the transmitter output pulse. The waveform generator

takes the MLT-3 three level encoded waveform and uses an

array of switched current sources to control the rise / fall time

and level of the signal at the output.

The output of the

switched current sources then goes through a lowpass filter in

order to "smooth" the current output and remove any high

frequency components. In this way, the waveform generator

preshapes the output waveform transmitted onto the twisted

pair cable to meet the pulse template requirements outlined in

IEEE 802.3. The waveform generator eliminates the need for

any external filters on the TP transmit output. The line driver

converts the shaped and smoothed waveform to a current

output that can drive 100 meters of category 5 unshielded

twisted pair cable or 150 ohm shielded twisted pair cable.

Transmitter - 10 Mbps

The operation of the 10 Mbps transmitter is much different

from the operation of the 100 Mbps transmitter. Even so, the

transmitter still consists of a waveform generator and line

driver. The purpose of the waveform generator is to shape the

output transmit pulse.

VT6103 Datasheet(PDF) 29 Page - VIA Technologies, Inc.