5 2005 Semtech Corp.
www.semtech.com
PROTECTION PRODUCTS
SMDA05C-8 through SMDA24C-8
Circuit Diagram
Connection Diagram
Device Connection for Protection of Eight Data Lines
The SMDAxxC-8 is designed to protect up to 8 data or
I/O lines. They are bidirectional devices and may be
used on lines where the signal polarities are above and
below ground.
The SMDAxxC-8 TVS arrays employ a monolithic struc-
ture. Therefore, the working voltage (V
RWM
) and break-
down voltage (V
BR
) specifications apply to the differen-
tial voltage between any two data line pins. For ex-
ample, the SMDA24C-8 is designed for a maximum
voltage excursion of ±12V between any two data lines.
The device is connected as follows:
z Pins 2, 3, 5, 6, 9, 10, 12 and 13 are connected to
the lines that are to be protected. Pins 1, 7, 8,
and 14 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. Pins 4 and 11 are
not connected.
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.
GND
GND
I/O 1
I/O 2
N.C.
I/O 3
I/O 4
GND
N.C.
GND
I/O 5
I/O 6
I/O 7
I/O 8
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Applications Information
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.
