Lightning and ESD Protection
for Gigabit Ethernet Interfaces
PROTECTION PRODUCTS - MicroClamp
®
Description
The
μClamp
®
2804L TVS diode is specifically designed
to meet the performance requirements of Gigabit
Ethernet interfaces. They are designed to protect
sensitive PHY chips from damage or upset due to
electrostatic discharge (ESD), lightning, electrical fast
transients (EFT), and cable discharge events (CDE).
The
μClamp2804L
is constructed using Semtech’s low
voltage EPD process technology. The EPD process
provides low operating voltages with significant reduc-
tions in leakage current and capacitance over silicon-
avalanche diode processes. The device features low
variation in capacitance over bias for stable operation
on GbE lines. This means the
μClamp2804L
will
introduce zero traffic frame errors on GbE interfaces
up to a PHY temperature of 100
o
C (100M Cat 5/5e
Cable). The
μClamp2804L
also features high surge
capability and can be used to replace existing SLVU2.8-
4 devices in applications where the device is placed on
the PHY side of the magnetics. In this configuration,
the device can withstand intra-building lightning surges
per Telcordia GR-1089.
The
μClamp2804L
is in a 8-pin SOIC package. The
leads are finished with lead-free matte tin. The combi-
nation of low clamping voltage, high surge capability,
and low loading capacitance makes the uClamp2804L
an ideal solution for protecting GbE systems to the
lightning immunity requirements of GR-1089.
uClamp2804L
Features
High ESD withstand Voltage:
+/-30kV
(Contact/Air)
per
IEC 61000-4-2
Able to withstand over 1000 ESD strikes per IEC
61000-4-2 Level 4
Flow-through design simplifies layout
Protects two line pairs
Low reverse current: 10nA typical (VR=2.8V)
Low variation in capacitance vs. bias voltage:
1.3pF
Typical (VR = 0 to 2.8V)
Working voltage: 2.8V
Solid-state silicon-avalanche technology
Mechanical Characteristics
JEDEC SO-8 package
Pb-Free, Halogen Free, RoHS/WEEE Compliant
Lead Finish: Matte tin
Molding compound flammability rating: UL 94V-0
Marking : Marking code, date code
Packaging : Tape and Reel
Applications
10/100/1000 Ethernet
Integrated magnetics/RJ-45 connectors
LAN/WAN Equipment
Security Cameras
Industrial Controls
Notebooks & Desktop Computers
Functional Circuit Diagram
Package Configuration
1.27
4.00 6.00
1
2
5.00
1.75
SO-8 (Max Dimensions in mm)
Revision 1/25/2011
1
www.semtech.com
uClamp2804L
PROTECTION PRODUCTS
Absolute Maximum Rating
R ating
Peak Pulse Power (tp = 8/20
μ
s)
Maximum Peak Pulse Current (tp = 8/20
μ
s)
ESD p er IEC 61000-4-2 (Air)
ESD p er IEC 61000-4-2 (Contact)
Op erating Temp erature
Storage Temp erature
Symbol
P
p k
I
p p
V
ESD
T
J
T
STG
Value
100
10
+/- 30
+/- 30
-40 to +85
-55 to +150
Units
Watts
Amps
kV
°C
°C
Electrical Characteristics (T=25
o
C)
Parameter
Reverse Stand-Off Voltage
Punch-Through Voltage
Snap-Back Voltage
Reverse Leakage Current
Clamping Voltage
Clamping Voltage
Variation in capacitance with
reverse bias
1
Symbol
V
RWM
V
PT
V
SB
I
R
V
C
V
C
Conditions
Minimum
Typical
Maximum
2.8
Units
V
V
V
I
PT
= 2
μ
A
I
SB
= 50mA
V
RWM
= 2.8V
I
PP
= 1A, tp = 8/20
μ
s
I
PP
= 10A, tp = 8/20
μ
s
Pins 1, 8 to 2, 7 and
pins 3, 6 to 4, 5
VR = 0 to 2.8V
f = 1MHz
3.5
2.8
3.8
4.3
0.01
0.05
5.5
10
μ
A
V
V
pF
1.3
Junction Capacitance
C
j
Pins 1, 8 to 2, 7 and
pins 3, 6 to 4, 5
VR = 2.8V, f = 1MHz
4.5
6
pF
Notes:
1) This parameter guaranteed by design and characterization and is not production tested
©
2011 Semtech Corp.
2
www.semtech.com
uClamp2804L
PROTECTION PRODUCTS
Non-Repetitive Peak Pulse Power vs. Pulse Time
10
Clamping Voltage vs. Peak Pulse Current
10
9
Clamping Voltage - V
C
(V)
8
7
6
5
4
3
2
1
Waveform
Parameters:
tr = 8μs
td = 20μs
Peak Pulse Power - P
PP
(kW)
1
0.1
0.01
0.1
1
10
100
Pulse Duration - tp (us)
0
0
2
4
6
8
10
12
Peak Pulse Current - I
PP
(A)
Normalized Junction Capacitance vs. Reverse Voltage
CH1 S21
Typical Insertion Loss (S21)
LOG
6 dB / REF 0 dB
1: -1.8892 dB
800 MHz
0 dB
-6 dB
-12 dB
5
12
2
1.8
1.6
Cj(V
R
) / Cj(V
R
=0V)
2: -2.1247 dB
900 MHz
3: -6.9338 dB
1.8 GHz
4: -15.047 dB
2.5 GHz
1.4
1.2
1
0.8
0.6
0.4
0.2
0
0
0.5
1
1.5
Reverse Voltage (V
R
)
3
-18 dB
-24 dB
-30 dB
4
f = 1 MHz
2
2.5
3
-36 dB
-42 dB
-48 dB
1
MHz
START . 030 MHz
10
MHz
100
MHz
3
1
GHz GHz
STOP 3000. 000000 MHz
ESD Clamping
(8kV Contact per IEC 61000-4-2)
ESD Clamping
(-8kV Contact per IEC 61000-4-2)
Note: Data is taken with a 10x attenuator
©
2011 Semtech Corp.
3
Note: Data is taken with a 10x attenuator
www.semtech.com
uClamp2804L
PROTECTION PRODUCTS
Applications Information
Device Connection Options for Protection of Four
High-Speed Data Lines
The uClamp2804L is designed to protect four high-
speed data lines (two differential pairs) from transient
over-voltages which result from lightning and ESD.
Data line inputs/outputs are connected at pins 1 and
8, 2 and 7, 3 and 6, and 4 and 5. The device is
designed such that PCB traces must remain unbroken
and routed through the device as shown in Figure 2.
Gigabit Ethernet Protection Solutions
When designing Ethernet protection, the entire system
must be considered. An Ethernet port includes
interface magnetics in the form of transformers and
common mode chokes. Transformers and chokes can
be discrete components, but integrated solutions that
include the RJ-45 connector, resistors, capacitors, and
protection are also available. In either case, the
transformer will provide a high level of common mode
isolation to external voltages, but no protection for
metallic (line-to-line) surges. During a metallic
transient event, current will flow into one line, through
the transformer and back to the source. As the
current flows, it charges the windings of the
transformer on the line side. Once the surge is
removed, the windings on the line side will stop
charging and will transfer its stored energy to the IC
side where the Ethernet transceiver or PHY IC is
located. The magnitude and duration of the surge is
attenuated by the inductance of the magnetics. The
amount of attenuation will vary by vendor and
configuration of the magnetics. It is this transferred
energy that must be clamped by the protection
circuitry.
A typical protection scheme which utilizes the
uClamp2804L
is shown in Figure 3. One device is
placed across two line pairs and is located on the PHY
side of the transformer as close to the magnetics as
possible. This is done to minimize parasitic inductance
and improve clamping performance. In this design, the
isolation voltage of the transformer is relied upon to
suppress common mode lightning surges.
The need
for a common mode protection device depends upon
the magnitude of the surge and the isolation rating of
the transformer. Most transformers are rated for at
least 1500V of common mode isolation. It is also
©
2011 Semtech Corp.
4
www.semtech.com
Figure 1 - Circuit Diagram
Figure 2 - Connection for Protection of Two
Differential Line pairs
uClamp2804L
PROTECTION PRODUCTS
Applications Information
important to make sure the resistor/capacitor
termination networks are rated accordingly.
Metallic
surges will be transferred in some form to the PHY
side and clamped by the
uClamp2804L. The amount of
energy will vary depending on the transformer, but will
be well within the surge handling capability of the
uClamp2804L.
The
uClamp2804L
will turn on when
the voltage across it exceeds the punch-through
voltage of the device. Low voltage turn on is important
since many PHY chips have integrated ESD protection
structures. These structures are for protection of the
device during manufacture and are not designed to
handle large amounts of energy. Should they turn on
before the external protection, they can be damaged
resulting in failure of the PHY chip.
As always, the final
design should be verified with testing.
Replacing SLVU2.8-4 in Existing Designs
The uClamp2804L can be used to replace SLVU2.8-4
in existing designs where the device is placed on the
PHY side of the transformer. This is true even though
the uClamp2804L is rated for a lower peak pulse
current than the SLVU2.8-4. The reason is that the
duration and magnitude of the input surge waveform
will be attenuated by the magnetics such that the
amount of energy that is delivered to the
uClamp2804L will be well within the capability of the
device.
Lightning Surge Test Results
During the metallic (line-to-line) surge test, the line
being stressed is tied to the surge generator with the
remaining lines tied together and connected to the
generator ground. Current will flow through the line
transformer transferring energy to the PHY side of the
transformer. Figure 4 shows the test set-up for
measuring the clamping voltage of the device. This set
up is designed to simulate the surge in an actual
gigabit Ethernet (GbE) circuit. A 100 Ohm resistor is
used to simulate the differential load of the PHY.
Figure 5 shows the clamping voltage of the
uClamp2804L
for a metallic mode 4000V (100A) 10/
700μs surge. The clamping voltage, measured at less
than 11 volts, provides sufficient clamping margin to
minimize electrical stress and is well below the failure
voltage range of typical GbE PHY chips that have been
tested by Semtech. The graph in Figure 6 shows the
typical clamping voltage of the
uClamp2804L
compared to the clamping voltage of the SLVU2.8-4.
An integrated magnetics module was used for the line
side magnetics/RJ-45. As shown, the clamping voltage
of both devices is nearly identical across the voltage
test range.
RJ-45
1
2
3
4
5
6
7
8
uClamp2804L
Gigabit
Ethernet
PHY
uClamp2804L
Figure 3 - GbE Protection to Lightning, ESD, and CDE
©
2011 Semtech Corp.
5
www.semtech.com
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