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 2005 Semtech Corp.

www.semtech.com

PROTECTION PRODUCTS

SMDA05 through SMDA24

Circuit Diagram

I/O Line Protection

Device Connection for Protection of Four Data Lines

The SMDAxx series of devices are designed to protect up

to four data lines. The devices are connected as follows:

The SMDAxx are unidirectional devices and are

designed for use on lines where the normal operat-

ing voltage is above ground. Pins 1, 2, 3, and 4 are

connected to the protected lines. Pins 5, 6, 7, and 8

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:

Place the TVS near the input terminals or connectors

to restrict transient coupling.

Minimize the path length between the TVS and the

protected line.

Minimize all conductive loops including power and

ground loops.

The ESD transient return path to ground should be

kept as short as possible.

Never run critical signals near board edges.

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 compared 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.

1

2

3

45

6

7

8

1

2

3

45

6

7

8

Ground

From Connector

To Protected

Device

Typical Connection

Applications Information