P R E L I M I N A R Y
ISLIC™
Intelligent Subscriber Line Interface Circuit
Le79R251 device
APPLICATIONS
ORDERING INFORMATION
Provides a cost-effective voice solution for long loop
applications providing POTS and integrated test
capabilities.
CO
DLC
PBX/KTS
Pair Gain
Device
Package
Le79R251JC
32-pin PLCC
DESCRIPTION
FEATURES
Monitor of two-wire interface voltages and currents
supports
— Voice transmission
— Through chip ring generation
— Programmable DC feed characteristics
– Independent of battery
– Current limited
— Selectable off-hook and ground-key thresholds
— Subscriber line diagnostics
– Leakage and Loop resistance
– Line capacitance and Bell
– Foreign voltage sensing
— Power cross and fault detection
Integrates through chip ringing
— High voltage operation supports long loops
— Provides the highest ringing capability in Legerity's
Intelligent Access Voice family.
Dual battery operation for system power saving
— Automatic high/low battery switching
— Intelligent thermal management
— +5 V and battery voltages required
Compatible with inexpensive protection networks
— Maintains longitudinal balance with low tolerance fuse
resistors or PTC thermistors
Provides pulse metering
— 12 kHz and 16 kHz
— Smooth polarity reversal
Tip-open state supports ground start signaling
Integrated test load switches/relay drivers
5 REN with 20 V DC offset trapezoid.
The Le79R251 device, in combination with an ISLAC™ device,
implements telephone line interface function. This enables the
design of a low cost, high performance, fully software
programmable line interface for multiple country applications
worldwide. All AC, DC, and signaling parameters are fully
programmable via microprocessor or GCI interfaces on the
ISLAC device. Le79R251 device has integrated self-test and
line-test capabilities to resolve faults to the line or line circuit.
Integrated test capability is crucial for remote applications
where dedicated test hardware is not cost effective.
RELATED LITERATURE
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—
—
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An ISLAC™ device must be used with this part.
080274 Am79D2251 Dual ISLAC Data Sheet
080250 Am79Q224x Quad ISLAC Data Sheet
080345 Am79R2xx/Am79D2251 Technical Reference
080344 Am79R2xx/Am79Q224x Technical Reference
BLOCK DIAGRAM
SA
HPA
Two-Wire
Interface
Longitudinal
Control
RSN
VTX
SB
Gain/Level
Shift
VLB
Attenuator
HPB
VSAB
BD
VREF
Signal
Conditioning
TMN
TMP
Thermal
Management
Control
IMT
ILG
CREF
Fault
Meas
TMS
VBP
VBL
Switch
Driver
VBH
Relay
Control
R2
R3
For US standard:
— drives ring up to 16.9 kft of 26 gauge wire.
or
— drives ring up to 26.8 kft of 24 gauge wire.
For European (British) standard:
— drives ring up to 6.5 km of 0.5 mm copper cable.
Signal
Transmission
AD
Input
Decoder
and
Control
Registers
Relay
Drivers
RYE
R1
P1
P2
P3
Relay Driver 1
BGND
LD
GND
VCC
Publication# 080253 Rev: A
Version: 1.0
Date: Sep 27, 2001
Le79R251 ISLIC™ Data Sheet
