LUCL9310GP-D datasheet(39/60 Pages) AGERE

39 / 60 page

Data Sheet

July 2001

Full-Feature SLIC, Ringing Relay, and Test Access Device

L9310 Line Interface and Line Access Circuit

Agere Systems Inc.

Supervision (continued)

Make-Before-Break Operation (continued)

With the make-before-break switch, there will be a

period of time (depending on ring signal frequency but

measured in tens of microseconds) where all four

switch contacts will be on. This means that the ring

generator will be connected through the current-limited

break switches to the input of the SLIC device. Current

will be limited by the break switch current limit, and this

will not damage the SLIC. This current may, however,

cause a false glitch at the NSTAT supervision output

that will need to be digitally filtered. The board designer

should consider any ramifications of this state on the

overall system or ring generator and battery design.

The major benefit of make-before-break switching is

that it will minimize any impulse noise generated during

ringing cadence. In many cases when operating the

switch in the make-before-break mode, no special

design to switch at zero current and voltage crossing is

required. Impulse noise generation when using solid-

state relays is documented in the

Impulse Noise and

the L758X Series of Solid State Switches Application

Note.

Break-Before-Make Operation

To achieve break-before-make, use the logic control

sequence device switching as shown below.

Table 20. Break-Before-Make Logic Control

Sequence Device Switching

The advantage of break-before-make operation is that

it eliminates the current spike when the ring access

relay changes state. The disadvantage is that it forces

an all-off state. Under inductive ringing loads, due to

Ldi/dt effects, may cause a reduction in the impulse

noise performance compared to make-before-break

switching.

Protection

External Protection

An external overvoltage clamp is required to ensure

that the off-state and on-state ratings of the solid-state

break switch and solid-state ring access switch are not

exceeded. The solid-state switches in the L9310 are

constructed in a dielectrically isolated high-voltage

technology. Because of the high device-to-device isola-

tion that is inherent in the dielectric isolation, only a tip

to ground and a ring to ground clamp is required. A tip

to ring overvoltage clamp is not needed. A foldback or

crowbar type device is recommended to minimize

power across the solid-state switches under a fault

condition.

The break switches and tip return switch are con-

structed from DMOS transistors. Because the on resis-

tance of the break switches is less than the tip side ring

return switch, the break switches are physically bigger

and have a higher current handling capability. Addition-

ally, the break switches have a foldback characteristic

which enables them to survive a higher on-state volt-

age (320 V) than the tip ring return switch (130 V),

which does not have the foldback characteristic. (See

the On-State Switch I-V Characteristics section.) The

ring access switch is a pnpn type device. Additionally,

the ring side will see the full power ring voltage, and the

tip side switch will see the power ringing voltage that is

attenuated by the ringing load, subscriber loop, feed

resistor, and protection resistors. Because of these dif-

ferences, the protection requirements on the tip side

are different from the protection requirements on the

ring side. Thus, it is recommended that an asymmetri-

cal (with respect to tip and ring) overvoltage protection

scheme be used.

Please contact your Agere Account Representative for

a recommended protection device.

Additionally, a series protection resistor with a fusible

characteristic or a PTC resistor is recommended to

limit current during lightning and power cross faults. A

minimum 50

Ω is recommended in tip and ring.

State

Break

Switches

Ring

Switches

Comment

Active/Scan

closed

open

—

Disconnect

(all-off)

open

hold

>8 ms

Ring

open

closed

—

Disconnect

(all-off)

open

hold

>8 ms

Active/Scan

closed

open

—

LUCL9310GP-D Datasheet(PDF) 39 Page - Agere Systems

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