TM
Document ID# 080248
Date:
Feb 18, 2005
Rev:
F
Version: 1
Distribution:
Public Document
Le79231
Intelligent Subscriber Line Interface Circuit
VE790 Series
APPLICATIONS
Enables a cost effective voice solution for long or short
loop applications providing POTS and integrated test
capabilities
-- CO
-- DLC
-- PBX/KTS
-- Pair Gain
FEATURES
Monitor of two-wire interface voltages and currents
supports
-- Voice transmission
-- Programmable DC feed characteristics
Independent of battery
Current limited
-- Selectable off-hook and ground-key thresholds
-- Subscriber line diagnostics
Leakage resistance
Loop resistance
Line capacitance
Bell capacitance
Foreign voltage sensing
-- Power cross and fault detection
Ring relay driver for external ringing
+5 V and battery supplies
Dual battery operation for system power saving
-- Automatic battery switching
-- Intelligent thermal management
Compatible with inexpensive protection networks
-- Accommodates low tolerance fuse resistors or PTC
thermistors
Metering capable
-- 12 kHz and 16 kHz
-- Smooth polarity reversal
Tip-open state supports ground start signaling
Integrated test load switches/relay drivers
Space Saving Package Options (8 x 8 QFN)
ORDERING INFORMATION
A VE790 series ISLACTM device must be used with this part.
1. Green package meets RoHS Directive 2002/95/EC of the European
Council to minimize the environmental impact of electrical equipment.
2. Due to size constraints, QFN devices are marked by omitting the
"Le" prefix. For example, Le79231QC is marked 79231QC.
Device
Package
Le79231JC
32-pin PLCC
Le79231DJC
32-pin PLCC (Green package)
1
Le79231QC
2
32-pin QFN
Le79231FQC
2
32-pin QFN (Green package)
1
DESCRIPTION
The Le79231 ISLIC device, in combination with a VE790 series
ISLACTM device, implements the 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
s i g n a l i n g pa r a m e t e r s a r e f u l l y p r o g r a m m a b l e v i a
microprocessor or GCI interfaces on the VE790 series ISLAC
devices. Additionally, the Le79231 ISLIC device has integrated
self-test and line-test capabilities to resolve faults to the line or
line circuit. The integrated test capability is crucial for remote
applications where dedicated test hardware is not cost
effective.
RELATED LITERATURE
080250 Le79Q2241x Quad ISLACTM Device Data Sheet
081065 Le79228 Quad ISLACTM Device Data Sheet
080262 VE790 Series Evaluation Board User's Guide
080804 Le79R2xx/Le79Q224x Chip Set User's Guide
080923 Le79R2xx/Le79228 Chip Set User's Guide
BLOCK DIAGRAM
Two-Wire
Interface
Thermal
Management
Control
Signal
Transmission
Gain/Level
Shift
Attenuator
Longitudinal
Control
Signal
Conditioning
Fault
Meas.
Input Decoder and
Control Registers
Switch Driver
Relay
Drivers
Relay
Driver 1
BGND
GND
VCC
Relay
Control
RSN
VTX
VLB
VSAB
VREF
IMT
ILG
CREF
P2
P3
P1
LD
AD
SA
HPA
HPB
SB
BD
TMN
TMP
TMS
VBL
R3
RYE
R2
R1
VBH
2
Le79231 VE790 Series Data Sheet
TABLE OF CONTENTS
Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Ordering Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Related Literature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Product Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Le79231 ISLIC Device Internal Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Features of the VE790 Series Chip set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Chip set Block Diagram - Four Channel Line Card Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Connection Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Pin Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Thermal Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Operating Ranges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Power Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
DC Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
Relay Driver Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Transmission Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
Current-Limit Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
Thermal Shutdown Fault Indications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
Operating Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
Operating Mode Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
Driver Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
Thermal-Management Equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
Timing Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
Application Circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
External Ringing Line card Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
Line card Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Physical Dimensions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
32-Pin PLCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
32-Pin QFN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Revision A to Revision B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Revision B to Revision C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Revision C to Revision D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Revision D to Revision E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Revision E to F1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Le79231 VE790 Series Data Sheet
3
PRODUCT DESCRIPTION
Legerity's VoiceEdge
family voice chip sets integrate all the functions of the subscriber line. Two chip types are used to
implement the line card
--
an Le79231 ISLIC device and a VE790 series ISLAC device. These provide the following basic
functions:
1. The Le79231 ISLIC device: A high voltage, bipolar device that drives the subscriber line, maintains longi-
tudinal balance and senses line conditions.
2. The VE790 series ISLAC devices: Low voltage CMOS ICs that provides conversion, control and DSP func-
tions for the Le79231 ISLIC device.
A complete schematic of the line card using a VoiceEdge chip set for external ringing is shown in the
Application Circuit, on
page 19
.
The Le79231 ISLIC device uses reliable, bipolar technology to provide the power necessary to drive a wide variety of subscriber
lines. It can be programmed by the VE790 series ISLAC device to operate in eight different modes that control power
consumption and signaling. This enables it to have full control over the subscriber loop. The Le79231 ISLIC device is designed
to be used exclusively with the VE790 series ISLAC devices. The Le79231 ISLIC device requires only +5 V power and the battery
supplies for its operation.
The Le79231 ISLIC device implements a linear loop-current feeding method with the enhancement of intelligent thermal
management. This limits the amount of power dissipated on the Le79231 ISLIC device by dissipating power in external resistors
in a controlled manner.
Each VE790 series ISLAC device contains high-performance circuits that provide A/D and D/A conversion for the voice (codec),
DC-feed and supervision signals. The VE790 series ISLAC devices contain a DSP core that handles signaling, DC-feed,
supervision and line diagnostics for all channels.
The DSP core selectively interfaces with three types of backplanes:
Standard PCM/MPI
Standard GCI
Modified GCI with a single analog line per GCI channel
The 790 series voice chip set provides a complete software configurable solution to the BORSCHT functions as well as complete
programmable control over subscriber line DC-feed characteristics, such as current limit and feed resistance. In addition, these
chip sets provide system level solutions for the loop supervisory functions and metering. In total, they provide a programmable
solution that can satisfy worldwide line card requirements by software configuration.
Software programmed filter coefficients, DC-feed data and supervision data are easily calculated with the WinSLAC
software.
This PC software is provided free of charge. It allows the designer to enter a description of system requirements. WinSLAC then
computes the necessary coefficients and plots the predicted system results.
The Le79231 ISLIC device interface unit inside the VE790 series ISLAC devices processes information regarding the line
voltages, loop currents and battery voltage levels. These inputs allow the VE790 series ISLAC devices to place several key
Le79231 ISLIC device performance parameters under software control.
The main functions that can be observed and/or controlled through the VE790 series ISLAC devices backplane interface are:
DC-feed characteristics
Ground-key detection
Off-hook detection
Metering signal
Longitudinal operating point
Subscriber line voltage and currents
Ring-trip detection
Abrupt and smooth battery reversal
Subscriber line matching
Ringing
Sophisticated line and circuit tests
To accomplish these functions, the Le79231 ISLIC device collects the following information and feeds it, in analog form, to the
Le79Q224x or Le79228 codecs:
The metallic (IMT) and longitudinal (ILG) loop currents
The AC (VTX) and DC (VSAB) loop voltage
The outputs supplied by the VE790 series ISLAC device to the Le79231 ISLIC device are then:
A voltage (VHL
i
*) that provides control for the following high-level Le79231 ISLIC device outputs:
4
Le79231 VE790 Series Data Sheet
DC loop current
12 or 16 kHz metering signal
A low-level voltage proportional to the voice signal (VOUT
i
)
A voltage that controls longitudinal offset for test purposes (VLB
i
)
The VE790 series ISLAC devices perform the codec and filter functions associated with the four-wire section of the subscriber
line circuitry in a digital switch. These functions involve converting an analog voice signal into digital PCM samples and converting
digital PCM samples back into an analog signal. During conversion, digital filters are used to band-limit the voice signals.
The user-programmable filters set the receive and transmit gain, perform the transhybrid balancing function, permit adjustment
of the two-wire termination impedance and provide frequency attenuation adjustment (equalization) of the receive and transmit
paths. Adaptive transhybrid balancing is also included. All programmable digital filter coefficients can be calculated using
WinSLAC software. The PCM codes can be either 16-bit linear two's-complement or 8-bit companded A-law or -law.
Besides the codec functions, the 790 series chip set provides all the sensing, feedback, and clocking necessary to completely
control the Le79231 ISLIC device functions with programmable parameters. System-level parameters under programmable
control include active loop current limits, feed resistance, and feed mode voltages.
The VE790 series ISLAC devices supply complete mode control to the Le79231 ISLIC device using the control bus (P1-P3) and
tri-level load signal (LD
i
).
The 790 series voice chip set provides extensive loop supervision capability including off-hook, ring-trip and ground-key
detection. Detection thresholds for these functions are programmable. A programmable debounce timer is available that
eliminates false detection due to contact bounce.
For subscriber line diagnostics, AC and DC line conditions can be monitored using built-in test tools. Measured parameters can
be compared to programmed threshold levels to set a pass/fail bit. The user can choose to send the measurement data directly
to a higher level processor by way of the PCM voice channel. Both longitudinal and metallic resistance and capacitance can be
measured, which allows leakage resistance, line capacitance, and telephones to be identified.
*Note:
i = channel number
Le79231 VE790 Series Data Sheet
5
LE79231 ISLIC DEVICE INTERNAL BLOCK DIAGRAM
AD
BD
SA
SB
RSN
VLB
IMT
ILG
+
-
+
-
=
0.01
+
-
+
-
+
-
+
VTX
HPA
HPB
VBH
VREF
IA sense
IB sense
VREF
VBL
LD
VCC
GND
Active Lo
w Batter
y
VREF
TMN
Thermal
Management
Control
BGND
VSAB
Decoder
Standb
y
OHT Fix
ed Longitudinal
V
olta
g
e
TMP
VREF
IB
600
IB
Demux
RD2
RD3
C1
C2
C3
RD1
Control Register
P1
P2
P3
Reser
ved
Gain/Level Shift
IA
600
TMS
Active High Batter
y
High Neg.
Bat. sel.
R1
R3
RYE
R2
Power amplifiers positive supply
BGND
To Power
Amplifiers
Tip Open
CREF
Thermal
Shutdown
Disconnect
Fault
Meas.
Fault
Meas.
IA
600
IB
600
+
IA
IB
600
600
-
IA
A Amplifier
B Amplifier
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