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May 2004

AN578

APPLICATION NOTE

POWER CROSSING

BEHAVIOUR OF LINE CARD PROTECTION

REV. 2A - 3601

INTRODUCTION

The purpose of this document is to explain the behaviour of LCP 150S/1511/1512 devices during the cou-

pling between a telecommunication line and a mains line.

TEST DIAGRAM

Figure 1 shows the test diagram. The mains 220 V 50 Hz is applied to the test assembly through an iso-

lation transformer. A relay driven by a mono-pulse generator allows the conducting time to be adjusted.

The current through the device is adjusted by a series resistor.

Figure 1. Test Diagram

MEASUREMENTS

During the tests three kinds of behaviour occur:

a) As shown in Figure 2 the device acts as a clamping device (non-firing) due to the small value of the

current which never exceeds the latching current of the structure.

220V

50Hz

1/1

TRANSFORMER

ISOLATION

RELAY

0to 4K

Line A

GND

GATE

LCPxxx

POWER SUPPLY

48V

+-