SRDA70-4TBT Ver la hoja de datos (PDF) - Semtech Corporation
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SRDA70-4TBT Datasheet PDF : 7 Pages
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SRDA70-4
PROTECTION PRODUCTS
Applications Information
Device Connection Options for Protection of Four
High-Speed Data Lines
The SRDA70-4 TVS is designed to protect four data
lines from transient over-voltages by clamping them to
a fixed reference. When the voltage on the protected
line exceeds the reference voltage (plus diode VF) the
steering diodes are forward biased, conducting the
transient current away from the sensitive circuitry.
Data lines are connected at pins 1, 4, 6 and 7. The
negative reference (REF2) is connected at pins 5 and
8. These pins should be connected directly to a ground
plane on the board for best results. The path length is
kept as short as possible to minimize parasitic induc-
tance.
The positive reference (REF1) is connected at pins 2
and 3. The options for connecting the positive refer-
ence are as follows:
I/O Protection
Microcontroller Protection
1. To protect data lines and the power line, connect
pins 2 and 3 directly to the positive supply rail (VCC).
In this configuration the data lines are referenced
to the supply voltage. An external TVS diode may
be added between the supply rail and ground in
order to prevent over-voltage on the supply rail.
2. The SRDA70-4 can be isolated from the power
supply by adding a series resistor between pins 2
and 3 and VCC. A value of 10kΩ is recommended.
The internal steering diodes remain biased, provid-
ing the advantage of lower capacitance.
3. In applications where no positive supply reference
is available, or complete supply isolation is desired,
an external TVS diode may be used as the refer-
ence. The steering diodes will begin to conduct
when the voltage on the protected line exceeds the
working voltage of the TVS (plus one diode drop).
SRDA70-4
Matte Tin Lead Finish
Matte tin has become the industry standard lead-free
replacement for SnPb lead finishes. A matte tin finish
is composed of 100% tin solder with large grains.
Since the solder volume on the leads is small com-
pared to the solder paste volume that is placed on the
land pattern of the PCB, the reflow profile will be
determined by the requirements of the solder paste.
Therefore, these devices are compatible with both
lead-free and SnPb assembly techniques. In addition,
unlike other lead-free compositions, matte tin does not
have any added alloys that can cause degradation of
the solder joint.
 2006 Semtech Corp.
4
www.semtech.com
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