LUCL9312AP-D AGERE [Agere Systems], LUCL9312AP-D Datasheet - Page 29

• Manufacturer Part Number: LUCL9312AP-D
• Description: Line Interface and Line Access Circuit Forward Battery SLIC and Ringing Relay for TR-57 Applications
• Manufacturer: AGERE [Agere Systems]

July 2001
Supervision
Break-Before-Make Operation
To achieve break-before-make, use the logic control
sequence device switching as shown below.
Table 15. Break-Before-Make Logic Control
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, it 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 L9312 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-
Agere Systems Inc.
Active/Scan
Disconnect
Ring
Disconnect
Active/Scan
(all-off)
(all-off)
State
Sequence Device Switching
(continued)
Switches
closed
closed
Break
open
open
open
Switches
Forward Battery SLIC and Ringing Relay for TR-57 Applications
closed
Ring
open
open
open
open
Comment
>8 ms
>8 ms
hold
hold
—
—
—
ally, the break switches have a foldback characteristic
that enables them to survive a higher on-state voltage
(320 V) than the tip ring return switch (130 V), which
does not have the foldback characteristic. (See 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
The overall device protection is achieved through a
combination of the external overvoltage and overcur-
rent devices, along with the integrated thermal shut-
down feature, the integrated window comparator,
the break switch foldback characteristic, and the
dc/dynamic current-limit response of the break and tip
return switches.
Active Mode Response at PT/PR
The line break switches and tip return switch are cur-
rent-limited switches. The current-limit mechanism lim-
its current through the switch to the specified dc current
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.
During a lightning fault (typical 1000 V 10 x 700 s
applied surge), the current-limited line break switches
will pass typically 2.5 A for 0.5 s before forcing the
break switches off. Once in the off state, the external
protection device must ensure that the off-state voltage
rating of 320 V is not exceeded. Note that the maxi-
mum differential voltage is the positive zener rating of
the protection device less the battery voltage, which
will appear on the line feed side of the switch.
is recommended in tip and ring.
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