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PROTECTION PRODUCTS

PROTECTION PRODUCTS

LC04-12

Configuring The LC04-12 for Central Office ADSL

Applications

For Central Office applications, the LC04-12 can be

configured for operation to 24V with the addition of

two external steering diodes. This is accomplished by

connecting two adjacent legs of the LC04-12 in series

and adding the steering diodes as shown in Figure 4.

Each of the TVS diodes has a working voltage of 12V.

Since the voltages are additive when series connected,

the device will have a working voltage of 24V. The

power rating of the device is effectively doubled since

the surge current capability remains unchanged.

During positive duration transients, the internal TVS

diodes of the LC04-12 will be reversed biased when

the line voltage exceeds 24V. Transient current will

flow through the LC04-12 to ground. For negative

duration transient, the external steering diodes (D1 &

D2) will be forward biased when the voltage exceeds

the forward voltage (V

The steering diodes are required to insure that the

internal compensation diodes of the LC04-12 are not

reverse biased as this would result in their destruction.

The ES1A ultrafast rectifiers have been found to work

well in this application. These devices will survive the

Bellcore 1089 (intra-building) and ITU K.20/K.21

surges and have a repetitive reverse voltage rating of

50V, and a typical junction capacitance of 10pF.

The total capacitance seen by the line will typically be

<25pF. This is determined by the sum of the capaci-

tance of the steering diode and 1/2 of the capacitance

of each line pair of the LC04-12.

Applications Information (Continued)