LUCL8574DP-D AGERE [Agere Systems], LUCL8574DP-D Datasheet - Page 27

• Manufacturer Part Number: LUCL8574DP-D
• Description: L8574D Resistive Subscriber Line Interface Circuit(SLIC), Ring Relay,and Protector(SRP)for Long Loop and TR-57 Applications
• Manufacturer: AGERE [Agere Systems]

Data Sheet
October 1998
Applications
Thermal Shutdown
If the silicon temperature rises above a nominal 145 C,
the L8574 will enter a thermal shutdown mode where
all switches are off and the SLIC is in a state that is
functionally equivalent to the disconnect state.
Relay Driver
The L8574 offers a single integrated relay driver. The
relay driver output RDO is low (relay operated) when a
low input on B3 is latched into the device. The driver
has sufficient driver capability to provide 70 mA with a
1.0 V drop and 20 mA with a 0.4 V drop. Turn-off and
turn-on times are a maximum of 10 s.
Solid-State Ringing Access
The L8574 offers a solid-state ringing access switch for
power ringing access and for the associated line break
function. During the Ringing state, unbalanced battery-
backed power ringing is applied to the Ring lead
through resistors R
SW3. The Ring drive amplifier of the L8574 SLIC is iso-
lated from the subscriber loop via the integrated line
break switch SW2 during the power ringing state. Since
the Tip lead of the L8574 SLIC is tied to ground via
resistor R
Tip lead. The return ground path for the power ringing
signal is via R
The line break switch, SW2, is implemented using a
high-voltage MOS transistor. This gives a linear V-I
characteristic, as seen in Figure 3. The ON resistance
of this switch is a nominal 50
This switch is current limited to a nominal 35 mA and
has a maximum off-state voltage rating of 320 V. The
ringing access switch, SW3, is implemented using a
pnpn type structure. This gives a linear V-I characteris-
tic with an offset through the origin, as shown in Figure
4. This offset is less than 3 V. The off-state voltage rat-
ing is 500 V. Surge current (10 s x 1000 s) through
this switch must be limited to less than 2 A. Steady
state current through this switch must be limited to less
than 150 mA.
Lucent Technologies Inc.
2
, no line break function is associated with the
2
.
(continued)
10
and R
1
via ringing access switch
Relay, and Protector (SRP) for Long Loop and TR-57 Applications
with a maximum 100 .
L8574D Resistive Subscriber Line Interface Circuit (SLIC), Ring
Battery Supplies
There are two battery pins on the L8574, V
V
mon negative battery voltage. The magnitude of the
battery should be sufficient to supply the required dc
current into the specified (long) loop requirement.
Integrated into the L8574 is solid-state switch, SW1.
SW1 has similar characteristics to the line break
switch, SW2, including the 35 mA current limit. When
SW1 is closed, the battery is applied through SW1 from
the V
ited by the current-limiting action of SW1. When SW1 is
open, the battery at V
internal current-limit circuit is associated with the V
node; thus, when the current-limit circuit is active, the
battery is applied to the subscriber loop through V
node and through the internal current-limiting circuitry,
limiting dc current to the subscriber loop to 28 mA.
When the current-limit circuit is not active, the voltage
battery at V
The state of SW1 and the current-limiting circuit is con-
trolled via logic inputs B0—B2. The L8574 state table
(Table 14) details, for a given operational state, the con-
dition of SW1 and the current-limit circuit.
dc Characteristics
V-I Characteristics
Resistors R
connected from battery to Ring, and R
from Tip to Ground. The dc loop current is fed to the
subscriber loop via these resistors. When the L8574 is
operating in the linear region of the V-I characteristic,
the dc feed resistance or slope of this region of opera-
tion is determined by the sum of resistors R
The slope of the V-I characteristic will be –1/400 .
When the L8574 is operating in the current-limited
region of the V-I characteristic, the current will be con-
stant, regardless of loop length, and will be set and
fixed by the internal current-limit circuit. The current
limit is internally fixed to a nominal 28 mA. Connect a
33 nF capacitor from C
slope of 1/10 k to the V-I characteristic in the current-
limited region of operation.
BAT2
BAT1
. These two nodes may be connected to a com-
node. dc current from the battery will be lim-
BAT2
1
and R
is isolated from the loop.
2
are the dc feed resistors. R
BAT1
LIM
is isolated from the loop. The
to V
BF
. Note that there is a
2
is connected
BAT1
1
plus R
and
1
is
BAT2
BAT2
2
.
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