AUGUST 1999 - REVISED FEBRUARY 2005

Specifications are subject to change without notice.

Customers should verify actual device performance in their specific applications.

TISP40xxL1AJ/BJ VLV Overvoltage Protectors

4-Wire Digital Systems (Continued)

Figure 12. 4-Wire System

AI4XAM

DC FEED

Th 9

SIGNAL

Th10

SIGNAL

TRANSFORMER COUPLED FOUR-WIRE INTERFACE

Th7

Th8

T3

T4

OVER-

CURRENT

PROTECTION

OVER-

CURRENT

PROTECTION

LINE 1

LINE 2

OVER-

CURRENT

PROTECTION

OVER-

CURRENT

PROTECTION

Th5

Th 6

Th1

Th2

Th 3

Th4

DC SUPPLY

SIGNAL

SIGNAL

T1

T2

For an HDSL d.c. feed voltage of 180 V or less and operation down to an ambient of -25 °C, the following Th1, Th2, Th3 and Th4 protectors

are suitable: TISP4250M3 or TISP4250H3, TISP3250H3 (combines Th1 and Th2 or Th3 and Th4) and TISP7250H3 (combines Th1, Th2 and

Th7 or Th3, Th4 and Th8). Possible overcurrent protection components are covered in the 2-wire digital systems clause.

For ISDN interfaces powered with ±40 V (ETSI, ETS 300 012 1992) the following Th1, Th2, Th3 and Th4 protectors are suitable: TISP4070M3

or TISP4070H3 or TISP4070L3, TISP3070F3 or TISP3070H3 (combines Th1 and Th2 or Th3 and Th4) and TISP7070F3 or TISP7070H3

(combines Th1, Th2 and Th7 or Th3, Th4 and Th8). At the terminating adaptor, the Th7 and Th8 protectors do not “see” the d.c. feed voltage

and should be selected to not clip the maximum signal level. Generally, the TISP40xxL1 series will be suitable.

Internal ISDN lines are not exposed to high stress levels and the chances of a.c. power intrusion are low (ETSI EN 300 386-2 1997).

Accordingly, the equipment port protection needs are at a lower level than ports connected to outside lines.

Home Phone Networking

Using the existing house telephone wiring, home phone networking systems place the local network traffic in a high band above the POTS and

ADSL (Asymmetrical Digital Subscriber Line) spectrum. Local network rates are 1 Mbps or more. To reject noise and harmonics, an in-line

protection and 5 MHz to 10 MHz bandpass filter module is used for the equipment. These modules are available from magnetic component

manufacturers (e.g. Bel Fuse Inc.) A typical circuit for the telephone line magnetics module is shown in Figure 13. Transformer T1 isolates the

equipment from the house wiring. The isolated winding output is voltage limited by a very low-voltage protector, Th1. With a differential voltage

of about 12 V peak to peak, the TISP4015L1 could be used for Th1. After filtering, connection is made to the differential transceiver of the

processing IC.

Figure 13. Home Phone Networking Isolation/filter/protection Circuit

AI4XAP

Th1

FILTER

C1

T1

TIP

RING

PROTECTION

HRTRX+

HRTRX-