1893CKLFT IDT, 1893CKLFT Datasheet - Page 33

• Manufacturer Part Number: 1893CKLFT
• Description: Ethernet ICs 3.3V 10/100 BASE TX INTEGRATED PHYCEIVER
• Manufacturer: IDT

Specifications of 1893CKLFT

• Rohs: yes
• Part # Aliases: ICS1893CKLFT

6.4.2 100Base-TX Operation: MLT-3 Encoder/Decoder
6.4.3 100Base-TX Operation: DC Restoration
6.4.4 100Base-TX Operation: Adaptive Equalizer
6.4.5 100Base-TX Operation: Twisted-Pair Transmitter
ICS1893CK-40, Rev. C, 06/02/09
When operating in the 100Base-TX mode, the ICS1893CK-40 TP-PMD sublayer employs an MLT-3
encoder and decoder. During data transmission, the TP-PMD encoder converts the NRZI bit stream
received from the PMA sublayer to a 3-level Multi-Level Transition code. The three levels are -1, 0, and +1.
The results of MLT-3 encoding provide a reduction in the transmitted energy over the critical frequency
range from 20 MHz to 100 MHz. The TP-PMD MLT-3 decoder converts the received three-level signal back
to an NRZI bit stream.
The ICS1893CK-40’s 100Base-TX operations uses a stream-cipher scrambler to minimize peak
amplitudes in the frequency spectrum. However, the nature of the stream cipher and MLT-3 encoding is
such that long sequences of consecutive zeros or ones can exist. These unbalanced data patterns produce
an undesirable DC component in the data stream known as ‘baseline wander’.
Baseline wander adversely affects the noise immunity of the receiver, because the ‘baseline’ signal moves
or ‘wanders’ from its nominal DC value. The ICS1893CK-40 uses a unique technique to restore the DC
component ‘lost’ by the medium. As a result, the design is very robust, immune to noise and independent
of the data stream.
The ICS1893CK-40 has a TP-PMD sublayer that uses adaptive equalization circuitry to compensate for
signal amplitude and phase distortion incurred from the transmission medium. At a data rate of 100 Mbps,
the transmission medium (that is, the cable) introduces significant signal distortion because of
high-frequency attenuation and phase shift. The high-frequency loss occurs primarily because of the cable
skin effect that causes the conductor resistance to rise as the square of the frequency rises.
The ICS1893CK-40 has an adaptive equalizer that accurately compensates for these losses in shielded
twisted-pair (STP) and unshielded twisted-pair (UTP) cables. The DSP-based adaptive equalizer uses a
technique that compensates for a wide range of cable lengths. The optimizing parameter for the
equalization process is the overall bit error rate of the ICS1893CK-40. This technique closes the loop on
the entire data reception process and provides a very high overall reliability.
The ICS1893CK-40 uses the same Twisted-Pair Transmit pins (TP_TXP and TP_TXN) for both 10Base-T
and 100Base-TX operations. Each twisted-pair transmitter module is a current-driven, differential driver
that can supply either of the following:
•
•
The ICS1893CK-40 interfaces with the medium through an isolation transformer (sometimes referred to as
a magnetic module). The ICS1893CK-40’s transmitter uses wave-shaping techniques to control the output
signal rise and fall times (thereby eliminating the need for external filters) and interfaces directly to the
isolation transformer.
Note:
1. In reference to the ICS1893CK-40, the term ‘Twisted-Pair Transmitter’ refers to the set of Twisted-Pair
2. For information on the 10Base-T Twisted-Pair Transmitter, see
A two-level 10Base-T (that is, Manchester-encoded) signal
A three-level 100Base-TX (that is, MLT-3 encoded) signal
Transmit output pins (TP_TXP and TP_TXN).
Twisted-Pair
ICS1893CK-40 Data Sheet Rev. C - Release
Transmitter”.
Copyright © 2009, Integrated Device Technology, Inc.
All rights reserved.
33
Section 6.5.11, “10Base-T Operation:
Chapter 6 Functional Blocks
June 2009