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PROTECTION PRODUCTS
PROTECTION PRODUCTS
SMS3.3
SMS3.3 Circuit Diagram
Protection of Four Unidirectional Lines
Device Connection for Protection of Four Data Lines
The SMS3.3 is designed to protect up to four unidirec-
tional data lines. The device is connected as follows:
1. Unidirectional protection of four I/O lines is
achieved by connecting pins 1, 3, 4 and 6 to the
data lines. Pin 2 and 5 are connected to ground.
The ground connections should be made directly to
the ground plane for best results. The path length
is kept as short as possible to reduce the effects
of parasitic inductance in the board traces.
Circuit Board Layout Recommendations for Suppres-
sion of ESD
Good circuit board layout is critical for the suppression
of ESD induced transients. The following guidelines are
recommended:
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.
Applications Information
