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PDF SR12 Data sheet ( Hoja de datos )
| Número de pieza | SR12 | |
| Descripción | Low Capacitance TVS Diode Array | |
| Fabricantes | Semtech | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de SR12 (archivo pdf) en la parte inferior de esta página. Total 8 Páginas | ||
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PROTECTION PRODUCTS
Description
RailClamps are surge rated diode arrays designed to
protect high speed data interfaces. The SR12 has been
specifically designed to protect sensitive components
which are connected to data and transmission lines from
overvoltages caused by ESD (electrostatic discharge), EFT
(electrical fast transients), and lightning.
The unique design of the SR12 incorporates four surge
rated, low capacitance steering diodes and a TVS diode
in a single package. During transient conditions, the
steering diodes direct the transient to either the positive
side of the power supply line or to ground. The internal
TVS diode prevents over-voltage on the power line,
protecting any downstream components.
The low capacitance array configuration allows the user
to protect two high-speed data or transmission lines.
The low inductance construction minimizes voltage
overshoot during high current surges.
SR12
RailClamp
Low Capacitance TVS Diode Array
Features
Transient protection for high speed data lines to
IEC 61000-4-2 (ESD) ±15kV (air), ±8kV (contact)
IEC 61000-4-4 (EFT) 40A (5/50ns)
IEC 61000-4-5 (Lightning) 0.5kV, 12A (8/20µs)
Array of surge rated diodes with internal TVS Diode
Protects two I/O lines
Operating Voltage: 12 volts
Low capacitance (5pF typical) for high-speed
interfaces
Low clamping voltage
Solid-state silicon-avalanche technology
Mechanical Characteristics
JEDEC SOT-143 package
UL 497B listed
Molding compound flammability rating: UL 94V-0
Marking : R12
Packaging : Tape and Reel per EIA 481
RoHS/WEEE Compliant
Applications
ADSL
Industrial Electronics
RS-422 Interfaces
Portable Electronics
Microcontroller Input Protection
WAN/LAN Equipment
Circuit Diagram
Pin 4
Pin 2
Pin 3
Schematic & PIN Configuration
4
1
Revision 04/11/05
Pin 1
23
SOT-143 (Top View)
1 www.semtech.com
1 page  
SR12
PROTECTION PRODUCTS
Applications Information (continued)
For negative events, the bottom diode will be biased
when the voltage exceeds the VF of the diode. At first
approximation, the clamping voltage due to the charac-
teristics of the protection diodes is given by:
VPCIN= VDCCe+scVrFipt(ifoonr spositive duration pulses)
VC = -VF
(for negative duration pulses)
However, for fast rise time transient events, the
effects of parasitic inductance must also be consid-
ered as shown in Figure 2. Therefore, the actual
clamping voltage seen by the protected circuit will be:
VC = VCC + VF + LP diESD/dt (for positive duration pulses)
VC = -VF - LG diESD/dt
(for negative duration pulses)
ESD current reaches a peak amplitude of 30A in 1ns
for a level 4 ESD contact discharge per IEC 1000-4-2.
Therefore, the voltage overshoot due to 1nH of series
inductance is:
Figure 1 - “Rail-To-Rail” Protection Topology
(First Approximation)
V = LP diESD/dt = 1X10-9 (30 / 1X10-9) = 30V
Example:
Consider a VCC = 5V, a typical VF of 30V (at 30A) for the
steering diode and a series trace inductance of 10nH.
The clamping voltage seen by the protected IC for a
positive 8kV (30A) ESD pulse will be:
VC = 5V + 30V + (10nH X 30V/nH) = 335V
This does not take into account that the ESD current is
directed into the supply rail, potentially damaging any
components that are attached to that rail. Also note
that it is not uncommon for the VF of discrete diodes to
exceed the damage threshold of the protected IC. This
is due to the relatively small junction area of typical
discrete components. It is also possible that the
power dissipation capability of the discrete diode will
be exceeded, thus destroying the device.
Figure 2 - The Effects of Parasitic Inductance
When Using Discrete Components to Implement
Rail-To-Rail Protection
The RailClamp is designed to overcome the inherent
disadvantages of using discrete signal diodes for ESD
suppression. The RailClamp’s integrated TVS diode
helps to mitigate the effects of parasitic inductance in
Figure 3 - Rail-To-Rail Protection Using
RailClamp TVS Arrays
2005 Semtech Corp.
5
www.semtech.com
5 Page | ||
| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet SR12.PDF ] | |
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