Note: Descriptions are shown in the official language in which they were submitted.
CA 02498587 2005-02-28
SURGE PROTECTION CIRCUIT
This application claims the benefit of the filing date of a provisional
application
having serial number 60/457,874 which was filed on February 26, 2004.
BACKGROUND OF THE INVENTION
A typical data communication system includes data communication equipment that
transmits data over a charnel provided by a transmission media such as a
cable. The
channel may be subjected to transient over-voltage conditions which may not
only impair
the data but also may damage the data communication equipment. A surge
protector may be
applied across the channel in an attempt to protect the system from such over-
voltage
conditions. However, the insertion of a surge protector in a channel or cable
may introduce
various types of signal loss and crosstalk. For example, insertion loss
results from the
insertion of the surge protector and is expressed as the reciprocal of the
ratio of the signal
power delivered to that part of the cable or line following the device to the
signal power
I S delivered to that same part before insertion of the device. Return loss is
a measure of signal
reflections occurring along a cable and is caused by various electrical
mismatches along the
cabling of the channel.
In addition, transmission of data over a data channel may introduce crosstalk
which
is a signal disturbance, such as noise or interference, caused by
electromagnetic coupling
from one signal path to another. Crosstalk measured at the end from which the
disturbing
signal is transmitted is referred to as near end cross talk (NEXT). Crosstalk
measured at the
opposite end from which the disturbing signal is transmitted is referred to as
far end cross
talk (FEXT). The Telecommunications Industry Association/Electronic Industry
Association (TIA/EIA) provides specifications and compliance requirements for
cabling
used in data communication systems operating at different data rates. For
example, category
CA 02498587 2005-02-28
specifies requirements for a system communicating up to 100 Mbps (Fast
Ethernet) and
category Se (enhanced) species data rates up to 1 Gbps.
What is needed is a category Se surge protector that provides transient
protection
while meeting industry standards such as signal loss and crosstalk for a
communication
5 cabling system.
SUMMARY OF THE INVENT1UN
The present invention overcomes the disadvantages of the prior art by
providing a
surge protector having transient protection that meets industry standards for
signal loss and
crosstalk specifications for a category Se cabling system.
in one embodiment, a surge protector is provided that includes at least one
surge
suppressor integrated circuit (IC) having first and second transient voltage
suppression
(TVS) diodes configured 2 per package for reducing crosstalk such as NEXT and
FEXT in a
high speed telecommunication line. A first and second general purpose (e.g.,
non-
telecommunication grade) fuse is coupled to the first and second TVS diodes
for reducing
signal loss such as insertion and return loss in the high speed
telecommunication line. This
configuration substantially meets category Se industry standards for signal
loss and
crosstalk.
The foregoing has outlined the present invention so that those skilled in the
art may
better understand the detailed description of the invention that follows.
Additional features
of the invention will be described hereinafter that form the subject of the
claims of the
invention. Those skilled in the art should appreciate that they. can readily
use the disclosed
conception and specific embodiment as a basis for designing or modifying other
structures
for carrying out the same purposes of the present invention and that such
other structures do
not depart from the spirit and scope of the invention in its broadest form.
BRIEF DESCRIPTION OF THE DRAWINGS
Other aspects, features, and advantages of the present invention will become
more
fully apparent from the following detailed description, the appended claims,
and the
accompanying drawings in which similar elements are given similar reference
numerals.
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CA 02498587 2005-02-28
FIG. 1 is a schematic diagram ofa surge protector according to one
embc>dimr;nt ul'
the present invention;
FIG. 2 is a top view of a surge suppressor IC of FIG. 1;
FIG. 3 is a pin layout of the surge suppressor IC of FIG. 2;
FIG. 4 is a schematic diagram of the surge suppressor IC of FIG. 2; and
FIG. 5 is a PCB layout of the surge protector of FIG. 1.
DETAILED DESCRIPTION
The present invention discloses a surge protector that provides tr~nsicnt
protection
and substantially meets category Se industry standards for signal loss and
crosstalk. The
surge protector includes at least one surge suppressor integrated circuit (IC)
having first and
second transient voltage suppression (TVS) diodes configured 2 per package for
reducing
emsstalk such as near end cross talk (NEXT) and far end cross talk (FEXT) for
a category
Se high speed telecommunication line. A first and second general purpose fuse
(e.g., non-
telecommunication grade) is coupled to the first and second TVS diodes for
reducing signal
loss such as insertion and return loss for a category Se high speed
telecommunication line.
Moreover, the TVS diodes can help provide transient protection by diverting an
input
overvoltage condition to the TVS diodes and away from computer/electrical
devices.
Referring to FIG. 1, shown is a a schematic diagram of a surge protector 10
according to an embodiment of the present invention. The surge protector 10
includes surge
suppressor ICs U1, U2, U3 and U4 which can be grouped or configured into
packages where
each package contains a pair of ICs and corresponding fuses. For example. U 1
and LJ? can
be configured to form one package and U3 and U4 can be configured to form
another
package. This arrangement can help reduce crosstalk such as FEXT and NEXT. In
particular, the arrangement of the surge protector 10 substantially meets the
energy handling
capability of the UL497B standard for transient protection and the category Se
channel
cabling requirements for high speed transmission lines.
In one application, surge protector 10 can be disposed between a transmitting
computer/electrical device (not shown) via a first connector Pl and a
receiving device (not
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CA 02498587 2005-02-28
shown) via a second connector P2. The terminals P1_1 through PI 8 of connector
Pl and
the terminals P2_1 through P2_8 of connector P2 can be arranged into 4 signal
line pairs
where each signal line pair is associated with a surge sttppressor IC and a
pair of fuses. The
first signal line pair includes a first signal line defined by terminals P1-1,
P2_l, conductors
S 30, 32 and fuse F1 and a second signal line defined by terminals P I ~2, P2
2, conductors 34.
36 and fuse F2. The second signal line pair includes a third signal line
defined by terminals
P1 3, P2 3, conductors 50, 52 and fuse F3 and a fourth signal line defined by
terminals
P1 6, P2 6, conductors 54, 56 and fuse F4. The third signal line pair includes
a fifth signal
line defined by terminals P1 4, P2 4, conductors 58, 60 and fuse FS and a
sixth signal line
defined by terminals PI 5, P2_5, conductors 62, 64 and fuse F6. The fourth
signal line pair
includes a seventh signal line defined by terminals P1 7, P2 7, conductors 66,
68 and fuse
F7 and an eighth signal line defined by terminals PI 8, P2 8, conductors 70,
72 and fuse
F8.
In one embodiment, connectors P1, P2 are category Se compliant connectors such
as
series 5164 8-pin registered jacks (RJ)-45 jacks manufactured by Stewart lnc.
for use in high
speed (1 Gbps) Ethernet data communication or telecommunication applications.
It should
be understood that the invention can be applied to other connector
configurations and other
transmission line speeds. Fuses F1 through F8 can be implemented as 8 in-line,
3 amperes,
250 VAC surface mount device (SMD) current limiting general purpose fuses (non-
telecommunication) such as those manufactured by Littlefuse Inc.
Surge suppressor circuits U1, U2, U3 and U4 provide transient protection for
each of
the 4 signal pairs. In particular, surge suppressor U I provides transient
protection for the
first signal pair, UZ provides transient protection for the second signal
pair, U3 provides
transient protection for the third signal pair and U4 provides transient
protection for the
fourth signal pair. A description of only suppressor U1 is provided below
since the
functionality of suppressors U2, U3 and U4 is similar to suppressor U 1.
Referring to FIGS. 2 through 4, shown is a detailed view of surge suppressor U
I of
the surge protector of FIG. 1. In one embodiment, U 1 (as well as U2, U3 and
U4) is a
microcircuit or IC for protecting components connected to high speed
telecommunication
lines (category Se) from surges. An example of such a circuit is the model
LC03-6 low
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CA 02498587 2005-02-28
capacitance TVS device for high speed data interfaces manufactured by Semtech
Corporation. The capacitance of the device, which is less than 25 Picofarads
for the
transmission of signals greater than 100 Megahertz, can be within a range of
10 to 60
Picofarads for signals of between 80 to 500 Megahertz. Such characteristics
help the surge
protector meet category Se requirements.
Surge suppressor U1 is shown configured for differential (line to line)
protection.
Surge suppressor U1 includes a diode bridge comprising four diodes 20, 22, 24,
26 and a
TVS diode 28 coupled across the bridge. The cathode of diode 24 and the anode
of diode 20
are connected to conductor 32 via pins I, 8. Similarly; the cathode of diode
26 and the
anode of diode 22 are connected to conductor 36 via pins 4. 5. The anode of
diodes 24. 26
and TVS diode 28 are to a common ground terminal via pins 2. 3 and 6. 7. The
cathode of
diodes 20, 22 and TVS diode 28 are connected together internally.
Referring to FIGS. I-4, suppressor circuit U 1 is capable of providing
overvoltage
protection for the first signal pair comprising first and second signal lines.
During an
I S overvoltage condition on the first signal line, an undesirable positive
transient having a
magnitude greater than the breakover point of TVS diode 28 and less than the
current level
of fuse F1 flows through terminal PI_1, conductor 30, fuse FI, conductor 32,
diode 20 and
TVS diode 28. TVS diode 28 conducts and passes the transient to the ground
terminal
thereby shunting the transient current away from a receiving electrical device
at terminal
P2_I. In a similar manner, a positive transient on the second signal line
having a magnitude
greater than the breakover point of TVS diode 28 and less than the current
level of luse F2
conducts through terminal Pl 2, conductor 34, fuse F2, conductor 36, of diode
22 and TVS
diode 28. TVS diode 28 conducts and passes the transient to the ground
terminal thereby
shunting the excess transient away from an electrical device at terminal P2 2.
On the other
hand, during normal operation (a non-overvoltage condition), a non-transient
signal flows
across terminals P1_1, P2_1 (or PI 2, P2 2) without being shunted to ground
because the
signal is not of a sufficient magnitude to cause TVS diode 28 to conduct.
FIG. 5 is a printed circuit board (PCB) layout 100 of the surge protector 10
of FIG. 1
according to an embodiment of the present invention. The components of the
surge
protector 10 can be configured to form 2 packages with each package consisting
of 2 groups
CA 02498587 2005-02-28
of ICs and corresponding fuses. For example, the first package can consist of
a first group
consisting of U1 and a parallel arrangement (i.e., side by side) of fuses FI
and F2 and a
second group of consisting of U2 and a parallel arrangement of fuses F3 and
F4. The
second package can consist of a third group consisting of U3 and a parallel
arrangement of
fuses FS and F6 and a forth group consisting of U4 and a parallel arrangement
of fuses h7
and F8. In addition, each group of each package can he contigured as a
transmission
channel, receive channel or a bidirectional channel. For example, the first
group ( U 1 ) can
be configured as a first transmission channel and the second group (U2) can be
configured
as a first receive channel. Likewise, the third group (U3) can be configured
as a second
transmission channel and the fourth group (U4) can be configured as a second
receive
channel. The above configuration helps reduce both NEXT and FEXT to achieve
category
Se requirements.
Other configurations having a similar functionality as the above configuration
are
possible. For example, the second group (U2) can be configured as a first
transmission
channel and the third group (U3) can be configured as a first rvceiv~ channel.
Likcwisc. the
first group (U l ) can be configured as a second transmission channel and the
fourth group
(U4) can be configured as a second receive channel.
While there have been shown and described and pointed out the fundamental
novel
features of the invention as applied to the preferred embodiments. it will be
understood that
various omissions and substitutions and changes of the form and details of the
structures and
circuits illustrated and in their operation may be made by those skilled in
the art without
departing from the spirit of the invention.
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