SM05_04 Datasheet, PDF (5/7 Pages) Semtech Corporation – TVS Diode Array

SM05 through SM36
PROTECTION PRODUCTS
Applications Information
Device Connection Options
The SM series is designed to protect one bidirectional
or two unidirectional data or I/O lines operating at 5 to
36 volts. Connection options are as follows:
z Bidirectional: Pin 1 is connected to the data line
and pin 2 is connected to ground (Since the device
is symmetrical, these connections may be re-
versed). The ground connection should be made
directly to a ground plane. The path length should
be kept as short as possible to minimize parasitic
inductance. Pin 3 is not connected.
z Unidirectional: Data lines are connected to pin 1
and pin 2. Pin 3 is connected to ground. For best
results, this pin should be connected directly to a
ground plane on the board. The path length should
be kept as short as possible to minimize parasitic
inductance.
Circuit Board Layout Recommendations for Suppres-
sion of ESD.
Good circuit board layout is critical for the suppression
of fast rise-time transients such as ESD. The following
guidelines are recommended (Refer to application note
SI99-01 for more detailed information):
z Place the TVS near the input terminals or connec-
tors to restrict transient coupling.
z Minimize the path length between the TVS and the
protected line.
z Minimize all conductive loops including power and
ground loops.
z The ESD transient return path to ground should be
kept as short as possible.
z Never run critical signals near board edges.
z Use ground planes whenever possible.
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.
 2004 Semtech Corp.
5
Device Schematic & Pin Configuration
RS-232 Transceiver Protection Example
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