TLK100_11 Datasheet, PDF (19/88 Pages) Texas Instruments – Industrial Temp, Single Port 10/100 Mb/s Ethernet Physical Layer Transceiver

TLK100
www.ti.com
SLLS931B – AUGUST 2009 – REVISED DECEMBER 2009
3.7 Cable Diagnostics
With the vast deployment of Ethernet devices, the need for reliable, comprehensive and user-friendly
cable diagnostic tool is more important than ever. The wide variety of cables, topologies, and connectors
deployed results with the need to non-intrusively identify and report cable faults. TI cable diagnostic unit
provides extensive information about cable integrity.
The TLK100 offers the following capabilities in its Cable Diagnostic tools kit:
1. Time Domain Reflectometry (TDR).
2. Active Link Cable Diagnostic (ALCD).
3. Digital Spectrum Analyzer (DSA)
3.7.1 TDR
The TLK100 uses Time Domain Reflectometry (TDR) to determine the quality of the cables, connectors,
and terminations in addition to estimation of the cable length. Some of the possible problems that can be
diagnosed include opens, shorts, cable impedance mismatch, bad connectors, termination mismatches,
and any other discontinuities on the cable.
The TLK100 device transmits a test pulse of known amplitude (1V) down each of the two pairs of an
attached cable. The transmitted signal continues down the cable and reflects from each cable
imperfection, fault, bad connector and the end of the cable itself. After the pulse transmission the TLK100
measures the return time and amplitude of all these reflected pulses. This technique enables measuring
the distance and magnitude (impedance) of non-terminated cables (open or short), discontinuities (bad
connectors), and improperly-terminated cables with an accuracy of ±1m.
To do this, the TLK100 uses a RAM with up to 256 samples to record all the input sampled data (Equals
to max possible measured cable length of over 200m). The TLK100 also uses soft data averaging to
reduce noise and improve accuracy. The TLK100 is capable of recording up to five reflections within the
tester pair. In case more than 5 reflections were recorded the TLK100 will save the last 5 of them.
For all TDR measurements, the transformation between time of arrival and physical distance is done by
the external host using minor computations (such as multiplication/addition and lookup tables). The host
must know the expected propagation delay of the cable, which depends, among other things, on the cable
category (e.g. CAT5/CAT5e/CAT6).
Copyright © 2009, Texas Instruments Incorporated
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