February 2012 Doc ID 16804 Rev 2 1/9
9
LCP1521S
Programmable transient voltage suppressor for SLIC protection
Features
■Programmable transient suppressor
■Wide negative firing voltage range:
VGn = -175 V max.
■Low dynamic switching voltages:
VFP and VDGL
■Low gate triggering current: IGT = 5 mA max.
■Peak pulse current: IPP = 30 A (10/1000 µs)
■Holding current: IH = 150 mA min.
Benefits
■A Trisil™ is not subject to ageing and provides
a fail safe mode in short circuit for a better level
of protection.
■Trisils are used to ensure equipment meets
various standards such as UL60950, IEC 950 /
CSA C22.2, UL1459 and FCC part 68.
■Trisils have UL94 V0 approved resin (Trisils
are UL497B approved [file: E136224]).
Description
These devices have been especially designed to
protect new high voltage, as well as classical
SLICs, against transient overvoltages.
Positive overvoltages are clamped by 2 diodes.
Negative surges are suppressed by 2 thyristors,
their breakdown voltage being referenced to -VBAT
through the gate.
These components present a very low gate
triggering current (IGT) in order to reduce the
current consumption on printed circuit board
during the firing phase.
TM: Trisil is a trademark of STMicroelectronics
Figure 1. Functional diagram
SO-8
LCP1521S
TIP
Gn
NC
RING
TIP
GND
RING
GND
1
www.st.com
Characteristics LCP1521S
2/9 Doc ID 16804 Rev 2
1 Characteristics
Table 1. Standards compliance
Standard
Peak
surge
voltage
(V)
Voltag e
waveform
Required
peak
current
(A)
Current
waveform
Minimum serial
resistor to meet
standard (Ω)
GR-1089 Core First level 2500
1000
2/10 µs
10/1000 µs
500
100
2/10 µs
10/1000 µs
12
24
GR-1089 Core
Second level 5000 2/10 µs 500 2/10 µs 24
GR-1089 Core
Intra-building 1500 2/10 µs 100 2/10 µs 0
ITU-T-K20/K21 6000
1500 10/700 µs 150
37.5 5/310 µs 110
0
ITU-T-K20 (IEC 61000-4-2) 8000
15000 1/60 ns ESD contact discharge
ESD air discharge
0
0
IEC 61000-4-5 4000
4000
10/700 µs
1.2/50 µs
100
100
5/310 µs
8/20 µs
60
0
TIA-968-A,
lightning surge type A
1500
800
10/160 µs
10/560 µs
200
100
10/160 µs
10/560 µs
22.5
15
TIA-968-A,
lightning surge type B 1000 9/720 µs 25 5/320 µs 0
Table 2. Thermal resistances
Symbol Parameter Value Unit
Rth(j-a) Junction to ambient 120 °C/W
LCP1521S Characteristics
Doc ID 16804 Rev 2 3/9
Figure 2. Electrical characteristics (definitions)
Figure 3. Pulse waveform
Table 3. Absolute ratings (Tamb = 25 °C)
Symbol Parameter Value Unit
IPP Peak pulse current
10/1000 µs
8/20 µs
10/560 µs
5/310 µs
10/160 µs
1/20 µs
2/10 µs
30
100
35
40
50
100
150
A
ITSM
Non repetitive surge peak on-state current
(50 Hz sinusoidal)
t = 20 ms
t = 200 ms
t = 1 s
18
10
7
A
VGn Negative battery voltage range -40 °C < Tamb < +85 °C -175 V
Tstg
Tj
Storage temperature range
Operating junction temperature range
-55 to +150
-40 to +150 °C
TLMaximum lead temperature for soldering during 10 s. 260 °C
V
R
I
PP
I
H
I
R
V
F
I
V
Symbol Parameter
I = Gate triggering current
V = Peak forward voltage LINE / GND
V = Gate triggering voltage
V = Forward drop voltage LINE /GND
I = Reverse leakage current GATE / LINE
I = Holding current
V = Reverse voltage GATE / LINE
V = Dynamic switching voltage GATE / LINE
LINE / GND
C = Capacitance LINE /GND
GT
FP
GT
F
RG
H
RG
DGL
I = Peak pulse current
I = Breakdown current
V = Forward drop voltage
PP
R
F
100
50
%I
PP
tt
rp
0
Pulse waveform
10/1000 µs:
t = 10 µs
t = 1000 µs
r
p
Characteristics LCP1521S
4/9 Doc ID 16804 Rev 2
Table 4. Parameters related to the diode LINE / GND (Tamb = 25 °C)
Symbol Test conditions Max. Unit
VFIF = 5 A t = 500 µs 3 V
VFP
10/700 µs
1.2/50 µs
2/10 µs
1.5 kV
1.5 kV
2.5 kV
RS = 10 Ω
RS = 10 Ω
RS = 62 Ω
5
9
30
V
Table 5. Parameters related to the protection thyristors (Tamb = 25 °C)
Symbol Test conditions Min. Max. Unit
IGT VLINE = -48 V 0.1 5 mA
IHVGn = -48 V 150 mA
VGT at IGT 2.5 V
IRG
VRG = -175 V
VRG = -175 V
Tj = 25 °C
Tj = 85 °C
5
50 µA
VDGL
VGn = -48 V(1)
1. The oscillations with a time duration lower than 50 ns are not taken into account.
10/700 µs
1.2/50 µs
2/10 µs
1.5 kV
1.5 kV
2.5 kV
RS = 10 Ω
RS = 10 Ω
RS = 62 Ω
IPP = 30 A
IPP = 30 A
IPP = 38 A
7
10
25
V
Table 6. Parameters related to diode and protection thyristors (Tamb = 25 °C)
Symbol Test conditions Typ. Max. Unit
IR
VGn / LINE = -1 V VLINE = -175 V
VGn / LINE = -1 V VLINE = -175 V
Tj = 25 °C
Tj = 85 °C
5
50 µA
CVLINE = -50 V, VRMS = 1 V, F = 1 MHz
VLINE = -2 V, VRMS = 1 V, F = 1 MHz
15
35 pF
Table 7. Recommended gate capacitance
Symbol Component Min. Typ. Max. Unit
CGGate decoupling capacitance 100 220 nF
LCP1521S Technical information
Doc ID 16804 Rev 2 5/9
2 Technical information
Figure 4. LCP concept behavior
Figure 4 shows the classical protection circuit using the LCP crowbar concept. This topology
has been developed to protect the new high voltage SLICs. It allows to program the negative
firing threshold while the positive clamping value is fixed at GND.
When a negative surge occurs on one wire (L1 for example) a current IG flows through the
base of the transistor T1 and then injects a current in the gate of the thyristor Th1. Th1 fires
and all the surge current flows through the ground. After the surge when the current flowing
through Th1 becomes less negative than the holding current IH, then Th1 switches off.
When a positive surge occurs on one wire (L1 for example) the diode D1 conducts and the
surge current flows through the ground.
Figure 5. Example of PCB layout based on LCP1521S protection
Figure 5 shows the classical PCB layout used to optimize line protection.
The capacitor C is used to speed up the crowbar structure firing during the fast surge edges.
This allows minimization of the dynamic breakover voltage at the SLIC Tip and Ring inputs
during fast strikes. Note that this capacitor is generally present around the SLIC - Vbat pin.
So to be efficient it has to be as close as possible from the LCP Gate pin and from the
reference ground track (or plan) (see Figure 5). The optimized value for C is 220 nF.
The series resistors Rs1 and Rs2 designed in Figure 4 represent the fuse resistors or the
PTC which are mandatory to withstand the power contact or the power induction tests
V
Ring
GND
Gn
TIP
RING
GND
-Vbat
C
Rs1
Rs2
L 1
L 2
V Tip
Th1 D1
T1
IG ID1
To
line side
220nF
GND To
SLIC side
Technical information LCP1521S
6/9 Doc ID 16804 Rev 2
imposed by the various country standards. Taking into account this fact the actual lightning
surge current flowing through the LCP is equal to:
I surge = V surge / (Rg + Rs)
With:
V surge = peak surge voltage imposed by the standard.
Rg = series resistor of the surge generator
Rs = series resistor of the line card (e.g. PTC)
e.g. For a line card with 30 Ω of series resistors which has to be qualified under GR1089
Core 1000V 10/1000 µs surge, the actual current through the LCP is equal to:
I surge = 1000 / (10 + 30) = 25 A
The LCP is particularly optimized for the new telecom applications such as the fiber in the
loop, the WLL, the remote central office. In this case, the operating voltages are smaller than
in the classical system. This makes the high voltage SLICs particularly suitable.
The schematics of Figure 6 give the most frequent topology used for these applications.
Figure 6. Protection of high voltage SLIC
Rs (*) = PTC or fuse resistor
Gn
GND
GND
TIP
RING
-Vbat
LCP1521S
220nF
SLIC
Rs (*)
Rs (*)
Line
Line card
TIP
RING
GND
Figure 7. Surge peak current versus overload
duration
Figure 8. Relative variation of holding
current versus junction
temperature
I (A)
TSM
0
4
8
12
16
20
24
1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03
t(s)
F=50Hz
Tjinitial=25°C
-40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90
0.7
0.8
0.9
1
1.1
1.2
1.3
T (°C)
j
I [T ] / I [T =25°C]
Hj Hj
LCP1521S Package information
Doc ID 16804 Rev 2 7/9
3 Package information
●Epoxy meets UL94,V0
●Lead-free package
In order to meet environmental requirements, ST offers these devices in different grades of
ECOPACK® packages, depending on their level of environmental compliance. ECOPACK®
specifications, grade definitions and product status are available at: www.st.com.
ECOPACK® is an ST trademark.
Figure 9. Foot print recommendations
Table 8. SO-8 dimensions
Ref.
Dimensions
Millimeters Inches
Min. Typ. Max. Min. Typ. Max.
A1.750.069
A1 0.1 0.25 0.004 0.010
A2 1.25 0.049
b 0.28 0.48 0.011 0.019
C 0.17 0.23 0.007 0.009
D 4.80 4.90 5.00 0.189 0.193 0.197
E 5.80 6.00 6.20 0.228 0.236 0.244
E1 3.80 3.90 4.00 0.150 0.154 0.157
e 1.27 0.050
h 0.25 0.50 0.010 0.020
L 0.40 1.27 0.016 0.050
L1 1.04 0.041
k° 0 8 0 8
ccc 0.10 0.004
E1
D
8
41
5
E
k
h x 45°
L
L1
C
(Seating
Plane) 0.25mm
(Gage Plane)
e
A
A2
bA1
ccc C
C
6.8
(0.268)
4.2
(0.165)
1.27
(0.050)
0.6
(0.024)
Ordering information LCP1521S
8/9 Doc ID 16804 Rev 2
4 Ordering information
5 Revision history
Table 9. Ordering information
Order code Marking Package Weight Base qty Delivery mode
LCP1521S CP152S SO-8 0.078 g 100 Tube
LCP1521SRL(1)
1. Preferred device
CP152S 2500 Tape and reel
Table 10. Document revision history
Date Revision Changes
20-Nov-2009 1 First issue.
23-Feb-2012 2 Standardized nomenclature for Gn.
LCP1521S
Doc ID 16804 Rev 2 9/9
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