LC04-12TB データシートの表示（PDF） - Semtech Corporation
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LC04-12TB Datasheet PDF : 8 Pages
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PROTECTION PRODUCTS
Applications Information (Continued)
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 (VF) of the device.
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.
LC04-12
ã 2000 Semtech Corp.
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