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ATTL7582BC

Tip Ring Access Switch

Agere -> LSI Corporation 

Data Sheet

November 1999

L7582 Tip Ring Access Switch

Switching Behavior (continued)

Table 11. Break-Before-Make Operation

ACCESS INPUT TSD

0V

5 V Float

5V

5 V Float

5V

5 V Float

0V

0 V Float

State

Timing

Power

—

Ringing

All Off Hold this state for ≤25 ms.

SW4 waiting for zero cur-

rent to turn off.

All Off Zero current has occurred

and SW4 has opened.

Idle/Talk Release break switches.

Break

Switches

1&2

Open

Open

Open

Closed

Ring

Return

Switch 3

Closed

Open

Open

Open

Ring

Access

Switch 4

Closed

Closed

Open

Open

Line Access

Switches

5&6

Open

Open

Open

Open

Notes:

Break-before-make operation can also be achieved using TSD as an input. In lines two and three of Table 11, instead of using the logic input pins

to force the all OFF state, force TSD to ground. This will override the logic inputs and also force the all OFF state. Hold this state for 25 ms. Dur-

ing this 25 ms all OFF state, toggle the inputs from 10 (ringing state) to 00 (idle/talk state). After 25 ms, release TSD to return switch control to

the input pins which will set the idle talk state.

When using the L7582 in this mode, forcing TSD to ground will override the INPUT pins and force an all OFF state. Setting TSD to 5 V will allow

switch control via the logic INPUT pins. However, setting TSD to 5 V will also disable the thermal shutdown mechanism. This is not recom-

mended. Therefore, to allow switch control via the logic INPUT pins, allow TSD to float.

Thus, when using TSD as an input, the two recommended states are 0 (overrides logic input pins and forces all OFF state) and float (allows

switch control via logic input pins and thermal shutdown mechanism is active). This may require use of an open collector buffer.

Also note that TSD operation in L7582 is different than TSD operation of the L7581, where application of 5 V does not disable the thermal shut-

down mechanism.

Power Supplies

Both the 5 V and battery supply are brought onto the

L7582. The L7582 requires only the 5 V supply for

switch operation; that is, state control is powered exclu-

sively off of the 5 V supply. Because of this, the L7582

offers extremely low power dissipation, both in the idle

and active states.

The battery voltage is not used for switch state control.

The battery is used as a reference voltage by the

integrated secondary protection circuit. When the volt-

age at TBAT or RBAT drops 2 V to 4 V below the battery,

the integrated SCR will trigger, thus preventing

fault-induced overvoltage situations at the TBAT/RBAT

nodes.

Loss of Battery Voltage

As an additional protection feature, the L7582 monitors

the battery voltage. Upon loss of battery voltage, the

L7582 will automatically enter an all OFF state and

remain in that state until the battery voltage is restored.

The L7582 is designed such that the device will enter

the all OFF state if the battery rises above –10 V and

will remain off until the battery drops below –15 V.

Monitoring the battery for the automatic shutdown fea-

ture will draw a small current from the battery, typically

4 µA. This will add slightly to the overall power dissipa-

tion of the device.

Impulse Noise

Using the L7582 will minimize and possibly eliminate

the contribution to the overall system impulse noise

that is associated with ringing access switches.

Because of this characteristic of the L7582, it may not

be necessary to incorporate a zero cross switching

scheme. This ultimately depends upon the characteris-

tics of the individual system and is best evaluated at

the board level.

Lucent Technologies Inc.

9

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