EQCO400T8 Datasheet, PDF (10/24 Pages) Microchip Technology – EQCO400T8 UTP Cable Equalizer

EQCO400T8
2.1 Guidelines for PCB Layout
Because signals are strongly attenuated by a long
cable, special attention must be paid on the PCB layout
between the RJ45 connector and the EQCO400T. The
EQCO400T8 should be as close as is practical to the
RJ45 connector. Traces between the RJ45, the
transformer and the EQCO400T8 should be either
single-ended 50Ω traces or, preferably, differential
traces with a differential impedance of 100Ω. To avoid
noise pickup, these traces should be placed as far away
as possible from other traces carrying digital signals or
fast switching signals. All differential traces should be
matched in length to minimize time of arrival skew.
For best EMC performance, identical common-mode
chokes should be used on the unused pairs to those
used on the signal pairs as shown in Figure 2-1. This
ensures the impedance seen by all conductors in the
UTP cable is the same.
A reference design is available on request.
2.2 Recommended Magnetics
The following magnetics are recommended for use
with EQCO400T:
TABLE 2-1: RECOMMENDED MAGNETICS
Component
Part Number
Transformers (1:1 with center tap)
Two per channel
Coilcraft WBC1-1TLB
Common-mode chokes
Four per channel
Coilcraft 1206USB-113MLB
Note: Operation with magnetics other than the recommended components cannot be guaranteed.
2.3 Connector Pins and Cable
Connection
The EQCO400T8 does not support auto-crossover. If
required, this must be implemented externally to the
device.
To be the same as 100BaseT Ethernet, IEEE Standard
1394-2008 recommends that data is transmitted on
RJ45 pins 1 and 2, and received on pins 3 and 6. If both
sides of the long-haul UTP connection are configured in
this way, a crossover cable or patch cord must be used.
If one side of the UTP connection transmits data on
RJ45 pins 1 and 2 and receives data on pins 3 and 6,
and the other side transmits data on RJ45 pins 3 and 6
and receives data on pins 1 and 2, a straight-through
cable must be used.
If maximum reach is the highest priority and if a closed
system is created, it is recommended to use pins 1 and
2 for transmit (receive) and pins 7 and 8 for receive
(transmit). This reduces near-end crosstalk (NEXT)
significantly, which will give a bonus on the maximum
cable span; especially for CAT5e.
2.4 Supplying Power over the UTP
Cable
The EQCO400T8 is fully compatible with the Power
Over Ethernet standard, allowing standard POE chip
sets to be used at the ends of the cable to transmit
power to a remote device. The unused pairs (RJ45 pins
4,5 and 7,8) are most easily used for the transmission
of power. The signal pairs can also be used as speci-
fied in the standard, but in this case, careful choice of
magnetic components is required to conform to both
the DC requirements of POE and the AC requirements
of IEEE-1394.
A POE reference design is available on request.
DS60001310B-page 10
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