Data Sheet
October 1998
L8574D Resistive Subscriber Line Interface Circuit (SLIC), Ring
Relay, and Protector (SRP) for Long Loop and TR-57 Applications
Features
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Low-power scan mode for low on-hook power dis-
sipation (55 mW max)
Low active power dissipation; talk or on-hook
transmission (240 mW max)
Distortion-free on-hook transmission
Eight operating states via latched paralleled data
inputs with channel select feature
Precision fixed 28 mA current limiter
Integrated protection
No external protection device required
Integrated ringing access relay
Ring trip detector
Loop closure detector with hysteresis
Relay driver
Battery noise cancellation
Thermal protection
44-pin, surface-mount, plastic package (PLCC)
Included in the L8574 are a solid-state ringing
access switch and a line break switch. Also included
is a relay driver for an external (test) access mechan-
ical relay.
State control is via four latched parallel data inputs. A
chip select feature allows the user to enable, disable,
or reset the data latches to a known logic state.
The L8574 offers a low-power scan state to minimize
power to less than 55 mW in the on-hook state. The
L8574 also supports on-hook transmission. The
active power in both the talk or on-hook transmission
mode is also very low (<240 mW). Current is limited
to a fixed value of 25 mA by an internal precision
current-limit circuit.
Because of the internal architecture of the L8574
SLIC and because of the power rating of the associ-
ated external feed resistors, the L8574 will meet most
surge requirements without use of an external sec-
ondary protection device. Internal circuitry steers
both positive and negative faults to fault ground. Neg-
ative faults are not dumped into battery.
The L8574 is a two-chip line interface solution pack-
aged in a single, 44-pin PLCC package. The Tip and
Ring drive amplifiers, the XMT amplifier, the receive
interface, and battery noise cancellation circuits are
fabricated in a 90 V complementary bipolar (CBIC)
process. The ring access switch, line break switch,
battery switch, current-limit, protection functions,
supervision, and control functions are fabricated in a
320 V dielectrically isolated bipolar-CMOS-DMOS
(BCDMOS) process. The device is available in a
44-pin PLCC package.
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Description
The L8574 is a resistive subscriber line interface cir-
cuit (SLIC) that is optimized for long loop applica-
tions, such as Bellcore TR-NWT-000057
requirements for digital loop carrier (DLC) applica-
tions. It interfaces the low-voltage circuits on an ana-
log line card to the Tip/Ring subscriber loop. The
L8574 does not supply dc current to the subscriber
loop; external resistors are used for this purpose.
AGERE [ AGERE SYSTEMS ]
