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ã 2000 Semtech Corp.

www.semtech.com

PROTECTION PRODUCTS

LCDA05 THRU LCDA24

Applications Information

Device Connection for Protection of Two High-Speed

Data Lines

The LCDAxx is designed to protect up to two high-speed

data lines. The LCDAxx utilizes a low capacitance

compensation diode in series with, but in opposite

polarity to a TVS diode in each line. The resulting

capacitance is less than 5pF per line. Each line will

only suppress transient events in one polarity. There-

fore, to achieve protection in both positive and nega-

tive polarity, a second TVS/rectifier pair is connected in

anti-parallel to the first. Pins 1, 2, 7, and 8 are used to

protect one data line. Pins 3, 4, 5, and 6 are used to

protect the second data line.

The device is connected as follows:

l

Pins 1 & 2 are tied together and pins 7 & 8 are tied

together providing the protection circuit for one I/O

line. Pins 3 & 4 are tied together and pins 5 & 6

are tied together providing the protection circuit for

the second I/O line. Since the device is electrically

symmetrical, either side of the connected pairs

may be used to protect the lines. The other side of

the pair is used to make the ground connection.

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:

l

Place the TVS near the input terminals or connec-

tors to restrict transient coupling.

l

Minimize the path length between the TVS and the

protected line.

l

Minimize all conductive loops including power and

ground loops.

l

The ESD transient return path to ground should be

kept as short as possible.

l

Never run critical signals near board edges.

l

Use ground planes whenever possible.

I/O 1

I/O 2

I/O 1

I/O 2

1

2

3

45

6

7

8

1

2

3

45

6

7

8

Line 1

In/Out

Line 1

Ground

Line 2

In/Out

Line 2

Ground

From Connector

To Protected

Device

1

2

3

45

6

7

8

Line 1

In/Out

Ground

Line 2

In/Out

From Connector

To Protected

Device

Connection Options

I/O Line Protection

LCDA Connection Diagram