SMP100LC

Application information

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Application information

In wireline applications, analog or digital, both central office and subscriber sides have to be

protected. This function is assumed by a combined series / parallel protection stage.

Figure 9.

Examples of protection stages for line cards

In such a stage, parallel function is assumed by one or several Trisil, and is used to protect

against short duration surge (lightning). During this kind of surges the Trisil limits the voltage

across the device to be protected at its break over value and then fires. The fuse assumes

the series function, and is used to protect the module against long duration or very high

current mains disturbances (50/60Hz). It acts by safe circuit opening. Lightning surge and

mains disturbance surges are defined by standards like GR1089, FCC part 68, ITU-T K20.

Figure 10.

Typical circuits

Figure 7.

Variation of thermal impedance

junction to ambient versus pulse

recommended pad layout)

Figure 8.

Relative variation of junction

capacitance versus reverse voltage

applied (typical values)

1E-3

1E-2

1E-1

1E+0

1E+1

1E+2

5E+2

1

10

100

t (s)

p

Z/R

th(j-a)

th(j-a)

C [V ] / C [V =2V]

RR

12

5

10

20

50

100

300

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

V (V)

R

F =1MHz

V

= 1V

T = 25°C

j

RMS

Line

Ring

relay

Line

Ex. Analog line card

Ex. xDSL line card or terminal

Fuse TCP 1.25A

T1

T2

SMP100LC-xxx

Typical circuit for subscriber side

Fuse TCP 1.25A

Tip S

Gnd

SMP100LC-xxx

Ring S

SMP100LC-xxx

Fuse TCP 1.25A

Tip L

Gnd

Ring L

Typical circuit for central office side