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www.protekdevices.com

05100.R5 4/05

PLC497

APPLICATION NOTE

The PLC497 is an ultra low capacitance, bidirectional array that is designed to protect I/O or high speed data lines from the damaging effects of ESD

or EFT. This product has a surge capability of 250 Watts P

DIFFERENTIAL-MODE CONFIGURATION (Figure 1)

The PLC497 is designed to protect one unidirectional line. Figure 1 shows a typical differential-mode (line to line) I/O port protection circuit applica-

tion. To achieve bidirectional protection, two PLC497 units are placed in parallel with opposing polarities within the circuit layout.

Circuit connectivity is as follows:

✔ Pins 1 and 2 of each device connected to datalines

✔ Pin 3 is not connected

COMMON-MODE CONFIGURATION (Figure 2)

The PLC497 can provide protection for sensor circuit applications. Figure 2 is a typical common-mode (line to ground) sensor circuit application. To

achieve bidirectional protection in this application, a second pair of TVS devices is added in parallel with opposing polarities where pins 2 are

connected to the line, pins 1 connected to ground and pins 3 unconnected.

Circuit connectivity is as follows:

✔ Pins 1 each device connected to datalines

✔ Pins 2 each device connected to ground

✔ Pin 3 is not connected

CIRCUIT BOARD LAYOUT RECOMMENDATIONS

Circuit board layout is critical for Electromagnetic

Compatibility (EMC) protection. The following guidelines

are recommended:

✔

The protection device should be placed near the

input terminals or connectors, the device will divert

the transient current immediately before it can be

coupled into the nearby traces.

✔

The path length between the TVS device and the

protected line should be minimized.

✔

All conductive loops including power and ground

loops should be minimized.

✔

The transient current return path to ground should

be kept as short as possible to reduce parasitic

inductance.

✔

Ground planes should be used whenever possible.

For multilayer PCBs, use ground vias.

Figure 1. Typical Differential-Mode i/o Port Protection Circuit

2

2

1

1

3

3

LINE 1 OUT

LINE 1 IN

LINE 2 OUT

LINE 2 IN

Figure 2. Typical Common-Mode Sensor Protection Circuit

SENSOR

CIRCUITRY

1

2

3

3

2

1

1

2

2

33

1