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LCDP1521
DUAL LINE PROGRAMMABLE TRANSIENT VOLTAGE SUPPRESSOR FOR SLIC PROTECTION
LCDP1521DUAL LINE PROGRAMMABLE TRANSIENT VOLTAGE
SUPPRESSOR FOR SLIC PROTECTION Dual line programmable transient voltage
suppressor Wide negative firing voltage range:
VMGL= -150V max. Low dynamic switching voltages: VFP and VDGL Low gate triggering current: IGT =5mAmax Peak pulse current: IPP=15A (10/1000 μs) Holding current:IH= 150 mA min
FEATURESThis device has been especially designed to
protect2 new high voltage, as well as classical
SLICs, against transient overvoltages.
Positive overvoltages are clamped by2 diodes.
Negative surges are suppressed by2 thyristors,
their breakdown voltage being referencedto -VBAT
through the gate.
This component presentsa very low gate
triggering current (IGT)in orderto reduce the cur-
rent consumption on printed circuit board during
the firing phase.
DESCRIPTIONA.S.D.™
FUNCTIONAL DIAGRAMTrisils are not subjectto ageing and providea fail
safe modein short circuit fora better protection.
Trisils are usedto help equipmentto meet various
standards suchas UL1950, IEC950/ CSA C22.2,
UL1459 and FCC part68. Trisils have UL94 V0
resin approved (Trisils are UL497B approved (file:
E136224)).
BENEFITS
LCDP1521 COMPLIANCES WITH THE FOLLOWING STANDARDS
THERMAL RESISTANCE
ELECTRICAL CHARACTERISTICS (Tamb= 25°C)
LCDP1521
ABSOLUTE RATINGS (Tamb= 25°C, unless otherwise specified).
tr: rise time (μs)
tp: pulse duration (μs)
ex: Pulse waveform 10/1000μs= 10μs tp= 1000μs
Repetitive peak pulse currentNote1:seetest circuitfor VFP;RSisthe protection resistor locatedontheline card.
PARAMETERS RELATED TO THE DIODE LINE/ GND (Tamb= 25°C)
LCDP1521
PARAMETERS RELATED TO DIODE AND PROTECTION THYRISTOR (Tamb= 25°C, unless otherwise
specified)
Note2:see functional holding current(IH)test circuit
Note3:seetest circuitfor VDGL
The oscillationswitha time duration lowerthan 50nsarenot takeninto account
PARAMETERS RELATED TO THE PROTECTION THYRISTOR (Tamb= 25°C unless otherwise specified)
LCDP1521
FUNCTIONAL HOLDING CURRENT (IH) TEST CIRCUIT: GO-NO GO TEST
TEST CIRCUIT FOR VFP AND VDGL PARAMETERS
LCDP1521
TECHNICAL INFORMATION
Fig. A1: LCDP1521 concept behavior.
Figure A1 shows the classical protection circuit using the LCDP1521 crowbar concept. This topol-
ogy has been developedto protect the new high voltage SLICs.It allowsto program the negative
firing threshold while the positive clamping valueis fixedat GND.
Whena negative surge occurson one wire (L1 for example),a currentIG flows through the baseof the
transistorT1 and then injectsa currentin the gateof the thyristor Th1. Th1 fires andall the surge current
flows through the ground. After the surge when the current flowing through Th1 becomes less negative
than the holding currentIH, then Th1 switches off.
Whena positive surge occurson one wire (L1for example), the diode D1 conducts and the surge current
flows through the ground.
The capacitorCis usedto speedup the crowbar structure firing during the fast surge edges.
This allowsto minimize the dynamical breakover voltageat the SLIC Tip and Ring inputs during fast
strikes. Note that this capacitoris generally present around the SLIC- Vbat pin.tobe efficientit hastobeas closeas possible from the LCDP1521 Gate pin and from the reference
ground track (or plan). The optimized value forCis 220nF.
The series resitors Rs1 and Rs2 designedin figure A1 represent the fuse resistorsor the PTC which are
mandatoryto withstand the power contactor the power induction tests imposedby the various country
standards. Taking into account this fact the actual lightning surge current flowing through the LCDPis
equalto: surge=V surge/ (Rg+ Rs)
With V surge= peak surge voltage imposedby the standard.= series resistorof the surge generator= series resistorof the line card (equivalentto PTC+Ron Fig. A2)
e.g. Fora line card with 60Ωof series resistors which hasto be qualified under GR1089 Core 1000V
10/1000μs surge, the actual current through the LCDP1521is equalto: surge= 1000/ (10+ 60)=
14AThe LCDP1521is particularly optimizedfor the new telecom applications suchas the fiberin the loop,
the WLL, the remote central office.In this case, the operating voltages are smaller thanin the classical
system. This makes the high voltage SLICs particularly suitable. The schematicsof figure A2 gives the
most frequent topology usedfor these applications.
