AN585 APPLICATION NOTE

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ISDN PROTECTION - PRODUCT RANGE

STMicroelectronics offers specific protection devices for ISDN interface protection. The product range is

given in Table 1, which shows that this function is available with different package versions.

Discrete and monolithic versions are available, in order to provide a wide choice of cost/performance com-

promises.

Depending on the solution chosen, different recommendations apply with regard to the optimum configu-

ration to use. Figure 2 illustrates the typical application schematic for TRIBALANCED PROTECTION.

When the discrete solution is used, three components per line are necessary.

Table 1. Tribalanced protection - product range

Figure 2. Tribalanced protection - functional schematic

APPLICATION SCHEMATICS

Figure 3 and 4 illustrate the use of tribalanced protection in a u-interface and an s-interface respectively.

In each case there is the choice of a discrete solution (SMTHDTxx or TPUxx) where a high surge capability

is required, or a single-chip solution for low cost (TPIxx). Thus cost a nd performance can be traded in a

variety of combinations. All of these components are innovative and ideal for use in high-speed transmis-

sion lines.

DISCRETE SOLUTION

(3 devices per line)

MONOLITHIC DEVICES

SOD15 / CB429

SO8 / DIL8

HIGH SURGE CAPABILITY

75A 10/1000 msec

MEDIUM SURGE CAPABILITY

30A 10/1000 msec

SMTHDT58 / TPU58

SMTHDT80 / TPU80

SMTHDT120 / TPU120

TPI8011P / TPI8012P

TPI12011P / TPI12012P

LOW CAPACITANCE LINE/GND

MONOLITHIC

SOLUTION

TPIxx

DISCRETE

SOLUTION

3 x SMTHDTXX / 3 x TPUxx

GOOD CAPACITANCE BALANCE A/LINE B

GOOD LONGITUDINAL BALANCE ON THE LINE

NO SIGNAL ATTENUATION