L3000N L3092
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L3000N - L3000N
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PABX COST REDUCTION PERFORMANCE IMPROVEMENT OBTAINED WITH SLIC CHIP
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L3000N/L3092 SLIC need very external components, very power ON-HOOK provide innovative functions like Ringing injection, message waiting, line length measurement autoadaptive systems.
Abstract SGS-THOMSON SLIC (Subscriber Line Interface Circuit) L3000N/L3092 suitable PABX (Private Automatic Branch Exchange), C.O. (Central Office) ISDN terminal adaptor applications described. chip approach allows integration innovative functions ringing generation injection, line length evaluation, message waiting, loop extension software programmable. High level DC/AC performances provided very power requested hook condition (less than 10mW from battery typ. 50mW from supplies). INTRODUCTION years represent transition period from fully analog solution fully digital (ISDN) PABX systems design. particular this systems generation analog digital line cards will coexist. SLICs this systems should satisfy following requirements: degrade transmission performances digital part (ex: noise relay bounces during ringing injection). Software programmability DC/AC characteristics order have easy adaptation different countries requirements. Signaling self management order simplify card controller software. number external components. High reliability cost. order satisfy above requirements complex circuit structure necessary. Such structure cannot integrated single chip because high voltage technology required interface subscriber line. Single chip solutions based present H.V. Technology possible only givAN382/1093
most above requirements increasing much device size external components number. SGS-THOMSON SLIC family actually production based chip approach able satisfy above requirements. fact only circuit directly connected line realized High Voltage Technology while control signal management functions performed control chip realized high density, Voltage Technology. (15V). addition this approach allows easy adaptation different applicative situation only selecting proper voltage control chip. following L3000N/L3092 deeply described. L3000N-L3092 GENERAL DESCRIPTION SLIC L3000N/L3092 integrate functions, except overvoltage protection, needed interface subscriber line. shown fig.1 L3000N chip directly connected telephone line. L3092 chip interfaces present. first analog interface (4W) connected analog input/output Codec/Filter. second parallel digital interface that allows different operating modes transfer information about line status. Because internal latches circuit this interface connected SLIC common control driven Line Card Controller (see fig. alternative this interface directly connected control port second generation COMBO SGS-THOMSON TS5070/TS5071 (see fig. main features L3000N/L3092 following Programmable feeding resistance limiting current (25/40/60mA) power dissipation (50mW) hook condition (off-hook detector active). Loop extension Integrated message waiting function.
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Signaling function (ON-HOOK/OFF-HOOK; GROUND-KEY/GROUND-START detection) Line length evaluation Hybrid function Line impedance synthesis (real/complex) Balanced ringing signal generation with zero crossing injection Automatic ringing stop with zero crossing when OFF-HOOK detected. Parallel latched digital interface direct connection with generation COMBO Card Controller number external standard tolerance components. Integrated thermal protection that disable output stages when junction temperature exceeds 140°C
Figure latched parallel digital interface L3092 allows easy common control structure. card controller select proper SLIC corresponding pin.
L3092
L3000N
LINE INTERFACE
L3092
L3000N
LINE INTERFACE
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Figure digital interface L3092 directly connected COMBOII ports. card controller manage this digital interface 2Mbit serial control port.
L3092
L3000N
LINE INTERFACE
L3092
L3000N
LINE INTERFACE
OPERATING MODES Three input output pins represent parallel digital interface. addition allows connect digital interfaces SLICs Line Card same control bus; digital datas applied this interface selects following operating modes: Conversation Active Mode Stand-by On-Hook Mode Power Down Disable Mode Ringing Mode CONVERSATION ACTIVE MODE SLIC setted this mode when off-hook condition been detected communication must activated; main functions performed this mode are: current feeding into subscriber loop. Signaling recognition (OFF-HOOK; GND-KEY; DIAL PULSES) Bidirectional transfer speech band signals between line (2wire) COMBO (4wire) interfaces. CHARACTERISTIC main SLIC function provide current subscriber loop order feed
properly connected telephone set. fig. different characteristics Line Current (Il) versus loop resistance (Rl) shown. curve represents characteristic obtained with traditional line interface based transformer; purely resistive characteristic (Il=VBAT/(2xRFS)) where typical values 200ohm 400ohm. (b), (c), curves represent three different programmable characteristics that obtained with L3000N/L3092 SLIC conversation mode. Each curve composed regions first with constant line current second resistive were value programmed means external resistor. constant current region allows power dissipation reduction with short lines compared with transformer solution. addition possibility program software different limiting currents (25,40,60mA) make system more flexible allowing easy adaptation different administration requirements possibility line length measurement. fact when TEST MODE function activated digital interface output will show actual line current equal lower than programmed limiting current value. possibility program three different limiting current values allows distinguish four different line resistances ranges shown fig. this information very useful order optimize transmission performances each line length.
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Figure curve represents characteristic obtained with traditional line interface based transformer. (b), (c), curves represent three different programmable characteristics that obtained with L3000N/L3092 SLIC conversation mode. L3000N/3092 Characteristic.
feeding resistance: 200; batt. voltage
particular second generation COMBO, SGS-THOMSON TS5070/71 adopted line length used select software proper transmit/receive gains balance impedances obtaining this autoadaptive system four states. Another important feature consists balanced line feeding circuit; means that line current variations will produce equal opposite voltage variations TIP, RING SLIC line terminations. This characteristic very important because during dial pulse selection line current change from zero maximum value producing large line voltage variations. balanced structure avoid high common mode signals generation with very short rise/fall time. should noted that this problem always present when monolithic SLICs with integrated DC/DC converter adopted fact this case doesn't exist voltage symmetry between line terminations. This kind common mode signals produce serious transmission problems ISDN line present same system; addition they also noise sources other analog lines. L3000N/L3092 SLIC been studied only order avoid common mode noise line, also less sensitive noise present battery voltage
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typically generated dial pulse selection ringing injection operations. particular noise battery voltage transferred line with attenuation higher than 20dB frequency components (10Hz) with more than 40dB speech band components (typ. 1kHz). LONG LINES FEEDING. L3000N/L3092 SLIC also suitable public central office, since this application sometimes required feed very long lines particular operating mode (Boost Battery) provided. When boost battery mode activated characteristic modified allowing 20mA feeding current 4Kohm loop resistance equivalent more than 10Km (see fig.4). Considering PABX dedicated Hotel applications this operating mode used perform "MESSAGE WAITING" function. fact when Boost Battery mode selected line current zero line voltage greater than 100V; this voltage high enough switch neon lamp telephone typically used inform subscriber call back operator. During Boost Battery operation L3000N line interface circuit internal output stages between negative battery (typ -48V) positive bat-
Figure characteristic Boost Battery mode allows feed very long lines (20mA/4Kohm) perform "message waiting" function. line current close zero TIP/RING voltage greater than 100V. L3000N/3092 Characteristic.
feeding resistance: 200; Boost Battery mode (tot. batt.: 120V)
tery voltage (typ. +72V) already present ringing operation. SIGNALING. When Conversation operating mode selected output pins digital interface following informations provided: ON-HOOK/OFF-HOOK detection GROUND GROUND START detection. addition off-hook detection delay very allowing dial pulse detection with distortion lower than contrary ground information filtered with time constant range 100ms. CHARACTERISTIC. L3000N/L3092 SLIC provide excellent characteristics, addition internal structure allows easy programming line balance impedances both real complex means external scaled components. means that case complex impedances external capacitors values will time lower than synthetized values. Another peculiarity L3000N/L3092 SLIC possibility recover insertion loss external protection resistors connected between SLIC
RING output pins line; such resistors cannot avoided being necessary limit line current when surges other causes produces overvoltages line. major part monolithic SLICs available market requires values external protection resistors 20ohm) being able recover attenuation produced such components. This attenuation become problem presence complex line impedance because value depends also frequency. protection resistors higher than 20ohm adopted correspondent amplitude distortion with frequency will acceptable external complex equalizing circuit required. contrary L3000N/L3092 SLIC allows protection resistors range from 100ohm increasing this system protection level. this condition guaranteed insertion loss flatness (including external protection resistors) between (line) (COMBO) interfaces 0.1dB both real complex line impedances. Another important L3000N/L3092 SLIC feature overall system performances capability work also presence high induced lon5/10
gitudinal line current. longitudinal current generated following causes: Magnetic/capacitive coupling between subscriber line main power distribution network (110/220V; 50/60Hz). Magnetic/capacitive coupling with adjacent subscriber line which large voltage/current variations present (ex: dial pulse selection; ringing injection.) Magnetic/capacitive coupling with high frequency electromagnetic waves. proper SLIC operation presence above conditions following characteristics necessary: High value Longitudinal Transversal Conversion (LTC) High value Longitudinal Transversal Conversion also presence high common mode current. High value Longitudinal Transversal Conversion also presence high frequency common mode current. L3000N/L3092 SLIC able satisfy above requirements; particular guaranteed value 52dB; typical 60dB. This value remain nearly unchanged also high common mode current (ex. 65mA peak each wire with transversal line current 50mA peak with 40mA transversal line current). addition high gain-bandwidth product L3000N integrated operational amplifiers allows keep value very high also common mode current frequencies 200/300kHz. Higher frequencies common mode current easily attenuated connecting between line terminations ground small capacitors (10/20nF). effect such capacitors SLIC parameters (gains, impedances, four wire conversion.) easily recovered acting SLIC external components thanks high flexibility chip architecture. fig.5 shown test circuit used evaluation 10MHz results obtained with without filtering capacitors line terminations. This excellent result show that L3000N/L3092 SLIC provide very high rejection signals without requiring expensive H.F. coils.
Figure Test circuit evaluation. BASIC TEST CIRCUIT CONFIGURATION MEASUREMENTS
L3092
L3000N
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Figure high bandwidth high current capability L3000N output operational amplifier allows excellent rejection longitudinal signals 200kHz curve. This good performances maintained higher frequencies using inexpensive small capacitors (Crf=10/20nF). L3000N/3092 measurements
Test circuit: Teil
STAND-BY ON-HOOK MODE L3000N/L3092 SLIC usually programmed Stand-By mode when connected telephone on-hook condition; only functions performed this mode are: line feeding with limiting current value (10mA) OFF-HOOK detection This second function performed sophisticate circuit that allows proper off-hook detection also presence high common mode currents induced line therefore off-hook information provided SLIC doesn't need additional processing card controller. reduced number functions provided this mode allows significative SLIC power dissipation reduction (150mW). POWER DOWN MODE This mode used those condition which necessary reduce zero power delivered line (power failure, emergency, line connected power down mode line interface circuit L3000N completely switched therefore able detect OFF-HOOK,
pedance line terminations 1Mohm current sinked from battery reduced zero. this mode power dissipation from +/-5V supplies typ. 50mW. case very power dissipation requested also when telephone on-hook such condition doesn't sink more than 500µA Automatic Stand-by Mode selected. Automatic Stand-by Mode combine advantages previous operating modes, particular: Accurate OFF-HOOK detection power consumption (50mW from +/-5V <10mW from battery). When this mode selected L3000N normally Power-Down Mode. dedicated circuitry inside L3092 will sense line voltage will automatically program Stand-by Mode L3000N possible off-hook condition detected. RINGING MODE L3000N/L3092 SLIC main characteristic possibility inject directly ringing signal line without request external electromechanical relay high level ringing
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generator. order obtain from L3000N proper level ringing signal additional positive voltage source requested (typically +72V). ringing signal obtained amplifying level signal (1.5Vrms) applied SLIC, this level oscillation obtained either from local oscillator from COMBO path. ringing signal injected line balanced mode with nominal amplitude 60Vrms that increased 70Vrms. During ringing injection SLIC output impedance just equal series protection resistors (dohm); this characteristic allows lower ringing signal amplitude compared with standard solutions where ringing generator series impedance typically 800ohm. fig.6 represented effect output impedance with different ringer load compared with traditional solution with source voltage 75Vrms 800ohm output impedance. dedicated circuitry guarantee that ringing signal injected disconnected from line always presence zero voltage crossing transition, avoiding generation very fast voltage transition line. During ringing injection sophisticate circuit will perform complete ring trip detection; when offhook condition recognized SLIC will automatically stop ringing signal without waiting card controller command. conclusion L3000N/L3092 SLIC allows save: centralized H.V. ringing generator ringing relays zero crossing circuitry software ring trip detection.
Figure Comparison between L3000N/L3092 SLIC standard solutions ringing performances. voltage across ringer load after line (280ohm) shown different (Ringer Equivalent Number). L3000N output impedance ringing mode allows recover lower source voltage (60Vrms versus 75Vrms) better than standard solution when increase. L30XX/3000N SLIC KITs
EFFECT OUTPUT IMPEDANCE DURING RINGING INJECTION (after line)
CONCLUSIONS complete circuitry needed interface system highways subscriber line shown fig.7. SLIC chip approach al8/10
lows reduce drastically number external components, save centralized ringing generator, ringing relay, zero crossing ringing control implement "message waiting" function. addition combination
L3000N/L3092 SLIC with COMBOII increase system flexibility performances. particular card controller select software: feeding currents (25/40/60mA) gains (25dB range; 0.1dB step) Balance networks Time slot assignment 64x2 slots) addition Test Mode implemented L3092 conjunction with COMBOII allows realize four step autoadaptivebalance system.
Figure Complete application circuit needed interface subscriber line with system highways. Very number external components high flexibility achieved SLIC chip architecture.
L3092
L3000N
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Information furnished believed accurate reliable. However, SGS-THOMSON Microelectronics assumes responsibility consequences such information infringement patents other rights third parties which result from use. license granted implication otherwise under patent patent rights SGS-THOMSON Microelectronics. Specifications mentioned this publication subject change without notice. This publication supersedes replaces information previously supplied. SGS-THOMSON Microelectronics products authorized critical components life support devices systems without express written approval SGS-THOMSON Microelectronics. 1995 SGS-THOMSON Microelectronics Rights Reserved SGS-THOMSON Microelectronics GROUP COMPANIES Australia Brazil France Germany Hong Kong Italy Japan Korea Malaysia Malta Morocco Netherlands Singapore Spain Sweden Switzerland Taiwan Thaliand United Kingdom U.S.A.
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