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LCP1521
SLIC PROTECTION
LCP1521PROGRAMMABLE TRANSIENT VOLTAGE
SUPPRESSOR FOR SLIC PROTECTION Dual programmable transient 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=30A (10/1000 μs) Holding current:IH= 150 mA min
FEATURESThis device has been especially designed to
protect 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. particular attention has been givento the internal
wire bonding. The Kelvin method configuration en-
sures reliable protection, reducing the overvoltage
introducedby the parasitic inductancesof the wiring,
especiallyfor very fast transients.
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
LCP1521 COMPLIANCES WITH THE FOLLOWING STANDARDS
THERMAL RESISTANCE
ELECTRICAL CHARACTERISTICS (Tamb= 25°C)
LCP1521
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)
LCP1521- PARAMETERS RELATED TO DIODE AND PROTECTION THYRISTOR (Tamb= 25°C, unless other-
wise specified)
Note2:see functional holding current(IH)test circuit
Note3:seetest circuitfor VDGL
The oscillationswitha time duration lowerthan 50nsarenot takeninto account
- PARAMETERS RELATEDTO THE PROTECTION THYRISTOR (Tamb =25°C unless otherwisespecified)
LCP1521
FUNCTIONAL HOLDING CURRENT (IH) TEST CIRCUIT: GO-NO GO TEST
TEST CIRCUIT FOR VFP AND VDGL PARAMETERS
LCP1521
TECHNICAL INFORMATION
Fig. A1: LCP1521 concept behavior.
Figure A1 shows the classical protection circuit using the LCP1521 crowbar concept. This topology
has been developedto protect the new high voltage SLIC’s.It allowsto program the negative firing
threshold while the positive clamping valueis fixedat GND.
Whena negative surge occurson one wire (L1for example)a currentIG flows through the baseof the tran-
sistorT1 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 (L1 for example) the diode D1 conducts and the surge current
flows through the ground.
Fig. A2: Exampleof PCB layout basedon LCP1521 protection. orderto minimize the remaining voltage across the SLIC inputs during the surge, the TIP and RING pins the LCP1521 are doubled (Pins1 and8for TIP/ Pins4 and5for RING).
This fact allows the board designerto connect the tracks likein figure A2. With sucha PCB design, the ex-
tra voltages causedby track stray inductance remain locatedon the line sideof the LCP anddo not affects
the SLIC side.
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 LCP1521 Gate pin and from the reference
ground track (or plan) (see Fig. A2). The optimized value forCis 220nF.