L9313 datasheet(6/40 Pages) AGERE

6 / 40 page

Data Sheet

September 2001

Full-Feature SLIC and Ringing Relay for TR-57 Applications

L9313 Line Interface and Line Access Circuit

Agere Systems Inc.

Description (continued)

A programmable external voltage source may be used

to provide software control of the overhead. The rate of

change of the overhead voltage may be controlled by

use of a single external capacitor at the CF1 node. If the

rate of change is uncontrolled, there may be audible

noise associated with this transition. Design equations

for this feature are given in the dc Characteristics sec-

tion of this data sheet.

If the overhead is not programmed via a resistor, the

device develops a default overhead adequate for a

3.14 dBm overload into 900

Ω. For the default over-

head, OVH is connected to ground.

Data control is via a parallel latched data control

scheme. Data latches are edge-level sensitive. Data is

latched in when the LATCH control input goes low.

While LATCH is low, the user cannot change the data

control inputs. The data control inputs may only be

changed when LATCH is high.

Incorporation of data latches allows for data control

information and loop supervision information to be

passed to and from the SLIC via data buses rather than

on a per-line basis, thus minimizing routing complexity

and board routing area.

A device RESET pin is included. When this pin is low,

the logic inputs are overridden and the device will be

reset into SLIC forward disconnect state and the switch

into the all-off state. NSTAT is forced to the on-hook

condition when RESET is low.

The overall device protection is achieved through a

combination of an external secondary protector, along

with an integrated thermal shutdown feature, a battery

voltage window comparator, the break switch foldback

characteristic, and the dc/dynamic current-limit

response of the break and tip return switches.

For protection against long duration fault conditions,

such as power cross and tip/ring shorts, a thermal shut-

down mechanism is integrated into the device. Upon

reaching the thermal shutdown temperature, the device

will enter an all-off mode. Upon cooling, the device will

re-enter the state it was in prior to thermal shutdown.

Hysteresis is built in to prevent oscillation. During this

mode, the NSTAT supervision output overrides the

actual loop status and forces an off-hook.

The line break switches and tip return switch are

current-limited switches. The current-limit mechanism

limits current through the switch to the specified dc cur-

rent limit under low frequency or dc faults (power cross

and/or tip/ring to ground short) and limits the current to

the specified dynamic current-limit response under

transient faults, such as lightning.

A foldover characteristic is incorporated into the line

break switches within their I-V curve. Under voltage

conditions higher than the normal operating range,

such as may be seen under an extreme lightning or

power cross fault condition, the line break switch will

fold over into a low-current state. This feature allows for

more relaxed specifications on the ring side protector,

thus allowing for higher-voltage ringing signals. (Tip

side protector is limited by the requirements on the tip

return switch.) This feature is part of the overall device

protection scheme.

This device uses a window comparator to force an all-

off condition if the battery drops below, or rises above,

a specified threshold.

Upon loss of VBAT1, the L9313 will automatically enter

an all-off mode. The device will enter this mode if the

magnitude of the battery drops below a nominal 15 V

and will remain in this mode until the magnitude of the

battery rises above a typical 20 V. During this mode,

the NSTAT supervision output will override the actual

hook status and force an off-hook or logic low.

When the device is in the scan mode, because of the

design of the scan clamp circuit, common-mode cur-

rent can be forced into or out of the battery supply.

Because of this, and depending upon power supply

design, the magnitude of the battery may rise above

the maximum operating condition during extended lon-

gitudinal currents or during a power cross fault condi-

tion. To prevent excess current from being forced into

or out of the battery, if the magnitude of the battery

rises typically above 75 V to 80 V, the device will enter

an all-off state. The device will remain in the all-off state

until the magnitude of the battery drops into the normal

operating range. During this mode, the NSTAT supervi-

sion output will override the actual hook status and

force an off-hook or logic low.

See the Protection section of this data sheet for more

details on device protection. Please contact your Agere

Account Representative for a recommended secondary

protection device.

Longitudinal balance is consistent with North American

TR-57 requirements.

Transmit and receive gains have been chosen to mini-

mize the number of external components required in

the SLIC-codec ac interface, regardless of the choice

of codec.

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