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ATTL7582AC

Tip Ring Access Switch

Agere -> LSI Corporation 

L7582 Tip Ring Access Switch

Data Sheet

November 1999

Switching Behavior (continued)

When using an L7582 in the make-before-break mode,

during the ring-to-idle transition, for a period of up to

one-half the ringing frequency, the ring break switch

and the pnpn-type ring access switch can both be in

the ON state. This is the maximum time after the logic

signal at INRING has transitioned that the ring access

switch is waiting for the next zero current cross, so it

can close. During this interval, current that is limited to

the dc break switch current-limit value will be sourced

from the ring node of the SLIC.

This current is presented to the internal protection cir-

cuit.

The SCR may turn on if:

s The SCR-type protector is used (A code)

s By random probability the ring-to-idle transition

occurs during a portion of the ring cycle when the

ringing voltage exceeds the protection circuit SCR

turn-on voltage.

s Current in excess of the SCR’s turn-on current is also

available.

Once the SCR is triggered on, if the SLIC is capable of

supplying current in excess of the holding current, the

SCR may be latched on by the SLIC.

The probability of this event depends on the character-

istics of the given SLIC and of the holding current of the

L7582A device. The SCR hold current distribution is

designed to be safely away from the test limit of

80 mA. The higher the distribution, the lower the proba-

bility of the latch.

If this situation is of concern for a given board design,

either use the A series device in the break-before-make

mode (eliminates the original 25 ms current pulse) or

use a B series device (eliminates the SCR).

Table 10. Make-Before-Break Operation

ACCESS INPUT TSD

State

Timing

Break

Switches

1&2

0V

5 V Float Power Ringing

—

Open

0V

0 V Float Make-before- SW4 waiting for next zero Closed

break

current crossing to turn off

maximum time—one-half of

ringing. In this transition

state, current that is limited

to the dc break switch cur-

rent-limit value will be

sourced from the ring node

of the SLIC.

0V

0 V Float Idle/Talk Zero cross current has

Closed

occurred.

Ring

Return

Switch

3

Closed

Open

Open

Ring

Access

Switch

4

Line

Access

Switches

5&6

Closed

Closed

Open

Open

Open Open

8

Lucent Technologies Inc.

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