Application information

SMP100MC

6/13

Doc ID 9699 Rev 5

2

Application information

In wire line 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 10.

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 circuits opening. Lightning surge and

mains disturbance surges are defined by standards like GR1089, TIA/EIA IS-968,

ITU-T K20.

Figure 8.

Variation of thermal impedance

junction to ambient versus pulse

duration

Figure 9.

Relative variation of junction

capacitance versus reverse voltage

applied (typical values)

Z/R

th(j-a)

th(j-a)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.E-02

1.E-01

1.E+00

1.E+01

1.E+02

1.E+03

tp(s)

Printed circuit board - FR4,

copper thickness = 35µm,

recommended pad layout

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1

10

100

1000

V (V)

R

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

RR

F =1MHz

V

= 1V

Tj = 25°C

OSC

RMS

Line

Ring

relay

Line

Ex. Analog line card

Ex. ADSL line card or terminal