Littelfuse Reference Designs
6
Reference Designs
6
Reference Designs
Customer Premises Equipment (CPE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2
Digital Set-top Box Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6
High Speed Transmission Equipment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-10
ADSL / VDSL Circuit Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-10
HDSL Circuit Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-12
ISDN Circuit Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-14
Pair Gain Circuit Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16
T1/E1/J1 Circuit Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-18
T1/E1/J1 Asymmetrical Circuit Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-21
Additional T1 Design Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-21
T3 Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-22
Analog Line Cards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-24
Battrax® Protection Gate Buffer Circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-41
PBX Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-43
CATV Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-44
Primary Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-47
Secondary Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-50
Triac Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-52
Data Line Protectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-53
LAN and VoIP Protectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-54
10Base-T Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-54
100Base-T Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-55
Note: The circuits referenced in this section represent typical interfaces used in
telecommunications equipment. SIDACtor devices are not the sole components
required to pass applicable regulatory requirements such as UL 60950, GR 1089, or
TIA-968-A (formerly known as FCC Part 68), nor are these requirements specifically
directed at SIDACtor devices.
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This section offers specific examples of how SIDACtor® devices can be used to ensure
long-term operability of protected equipment and uninterrupted service during transient
electrical activity. For additional line interface protection circuits, see "Regulatory Compliant
Solutions" on page 7-46.
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CPE is defined as any telephone terminal equipment which resides at the customer’s site
and is connected to the Public Switched Telephone Network (PSTN). Telephones,
modems, caller ID adjunct boxes, PBXs, and answering machines are all considered CPE.
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CPE should be protected against overvoltages that can exceed 800 V and against surge
currents up to 100 A. In Figure 6.1 through Figure 6.6, SIDACtor® devices were chosen
because their associated peak pulse current (IPP) rating is sufficient to withstand the
lightning immunity test of TIA-968-A without the additional use of series line impedance.
Likewise, the fuse shown in Figure 6.1 through Figure 6.6 was chosen because the
amps2time (I2t) rating is sufficient to withstand the lightning immunity tests of TIA-968-A
without opening, but low enough to pass UL power fault conditions.
The following regulatory requirements apply:
• TIA-968-A (formerly known as FCC Part 68)
• UL 60950
All CPE intended for connection to the PSTN must be registered in compliance with
TIA-968-A. Also, because the National Electric Code mandates that equipment intended for
connection to the telephone network be listed for that purpose, consideration should be
given to certifying equipment with an approved safety lab such as Underwriters
Laboratories.
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Figure 6.1 through Figure 6.6 show examples of interface circuits which meet all applicable
regulatory requirements for CPE. The P3100SB and P3100EB are used in these circuits
because the peak off-state voltage (VDRM) is greater than the potential of a Type B ringer
superimposed on a POTS (plain old telephone service) battery.
150 VRMS √2 + 56.6 VPK = 268.8 VPK
Note that the circuits shown in Figure 6.1 through Figure 6.6 provide an operational solution
for TIA-968-A. However TIA-968-A allows CPE designs to pass non-operationally as well.
For a non-operational solution, coordinate the IPP rating of the SIDACtor device and the I2t
rating of the fuse so that (1) both will withstand the Type B surge, and (2) during the Type A
surge, the fuse will open. (See Table 8.2, Surge Rating Correlation to Fuse Rating on page
8-17.)
Note: For alternative line interface protection circuits, see "Regulatory Compliant Solutions"
on page 7-46.
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04611.25
Tip
P3100SB
or
P3100EB
To Protected
Components
Ring
Figure 6.1
Basic CPE Interface
Transmit / Receive
04611.25
+
Tip
-
P3100SB
or
P3100EB
Ring
+
Figure 6.2
4GHGTGPEG&GUKIPU
Ring
Detect
Transformer Coupled Tip and Ring Interface
04611.25
Tip
P3100SB
or
P3100EB
Relay
Transmit/
Receive
Circuitry
Ring
Ring
Detect
Figure 6.3
Modem Interface
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Transistor
Network
Interface
Hook Switch
04611.25
Tip
Ring
Option 1
P3100SB
or
P3100EB
Ringer
Dialer
IC
Figure 6.4
Speech
Network
DTMF
Handset
CPE Transistor Network Interface—Option 1
Transistor
Network
Interface
Hook Switch
04611.25
Tip
Ring
Ringer
Option 2
P1800SB
or
P1800EB
Dialer
IC
Figure 6.5
DTMF
Speech
Network
Handset
CPE Transistor Network Interface—Option 2
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&XVWRPHU3UHPLVHV(TXLSPHQW&3(
04611.25
Tip
Transistor
Network
Interface
P3100SB
or
P3100EB
Ring
Ring
Detect
Note: Different Ground References Shown.
04611.25
Tip
Transistor
Network
Interface
P3100SB
or
P3100EB
Ring
Ring
Detect
Two-line CPE Interface
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Figure 6.6
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The set-top box consists of power supply and signal ports. Some of the more recent highend designs also can have a hard drive to facilitate program recording. Unlike traditional
analog boxes, the digital devices are more like computers and so have many of the same
system and port features.
Cable, satellite, and terrestrial set-top boxes are similar designs with software variations.
Digital broadband media (DBM) devices are home gateway devices, offering services
including Video On Demand, TV web browsing, email, and communication services.
Figure 6.7 shows an example of the use of Littelfuse products in a set-top box design. (Data
sheets for the protection solutions highlighted in the illustration can be found in this
Telecom Design Guide.)
RF O/P
SL1002A230SM
RF I/P
SL1002A230SM
RF Tuner
A/D
Demod
SMART Card I/F
Smart Card
Reader
NTSC/PAL
Encoder
Graphics
Controller
Modem
0461 1.25
V18MLE0603
Y/C (mini DIN)
'S Video'
V18MLE0603
MPEG 2 AV
Decoder
Audio I/F
Telephone Line
CVBS
(RCA Jack)
Audio Pre-amp
Tip
SCART
<150 Mbps:
V18MLE0603, SP724
>150 Mbps:
PGB1010603
Ring
P3100SB
CPU
USB Port
RS 232
V18MLE0603
Hard Disk Drive
USB1.1:
MHS Series
AC I/P
Line
219XA
C-III series MOV
PSU
Neutral
C-III series MOV
HV275
Figure 6.7
Block Diagram of Set-top Box
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The following agency standards and industry regulations may apply to digital set-top boxes:
•
•
•
•
•
•
IEC 61000-4
ANSI/IEEE C62.41
TIA-968-A
UL 60950
Telcordia GR 1089
ITU K.20 and K.21
3RZHU6XSSO\
The AC connection can be either a two-wire design (either a live or hot with neutral) or a
three-wire design that additionally uses the Ground (earth) connection. In both designs
using a fuse for overcurrent protection may be mandatory and using varistors (MOVs) to
provide overvoltage protection may be beneficial.
A two-wire solution is a 219XA series 5x20 mm glass fuse used with a C-III series MOV (up
to two parts).
In a three-wire system it is possible to connect MOVs across all three conductors (H-N,
H-G, and N-G (or L-N, L-G, and N-G). For use in the United States, the device must meet
UL 1414 standards, requiring no leakage from H-G (L-G) through the MOV. Typically, an
isolation device is used in series with the MOV to pass the UL certification.
The Littelfuse HV 275 device meets the requirement for a 120 V AC system: 219XA series
5x20 mm glass fuse used with a C-III series MOV (up to three parts) along with the HV 275.
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Various communication ports are applicable.
The video signal feeds into the set-top box through a co-ax connector from a satellite
receiver, a cable company, or a terrestrial antenna. Because of the high frequency of these
signals, only very low capacitance protectors can be deployed. Because the feed is from an
external source, a high surge rating is usually required and virtually all solutions use a gas
plasma arrester for protection. Figure 6.8 shows the recommended solution for satellite
receiver protection.
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Video Signal Input
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LNB supply
P2600SB
Satellite F connector
SL1002A230SM
Figure 6.8
Satellite Receiver Protection
Some boxes have both the standard UHF connector to accept terrestrial antenna and the
F-type connector used for cable and satellite connections and can support both inputs. In
these cases both satellite and the UHF co-ax inputs can use gas plasma arresters for
protection.
Solutions include SL1002A090SM or SL1002A230SM.
Video Output
The set-top box has to connect to either a conventional TV set or monitor. The two most
common connectors are co-ax or SCART (Syndicat des Constructeurs d’Appareils
Radiorécepteurs et Téléviseurs). Like the co-ax inputs, the co-ax output will need a lowcapacitance device to be protected.
The multi-pin SCART is a suitable application for a low-capacitance array. On some
designs using two SCARTs facilitates recording and viewing. A six-pin device is common.
One solution is the SP05xx series diode array.
Modem Port
A modem port is featured on many designs to facilitate interactive services such as Pay Per
View (PPV) and Interactive Pay Per View (IPPV). The modem port requires similar threat
protection as the conventional twisted pair telephone connections. The classic overvoltage
protection and resettable overcurrent protection can be deployed in this circuit.
Solution examples include SIDACtor® P3100SB, SL1002A600SM, PTC, and TeleLink®
fuse. Solutions may vary depending on the end market.
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Audio Output
A stereo jack socket often is provided for home theater applications. While the signal
frequency is low and a variety of overvoltage protection can be used, the main concern is
electrostatic discharge (ESD).
Solutions include TVS diode Arrays, or Multilayer Varistors.
USB Port
USB ports are provided to support digital cameras, printers, and MP3 players as well as
legacy devices. New designs use USB 2.0.
USB 1.1 solutions include Multilayer Varistors or TVS diode Arrays. The USB 2.0 solution
uses the PGB1010603.
RS 232
RS 232 serial ports are used for game pads, upgrades, and diagnostics as well as legacy
devices.
One protection solution for the RS 232 interface is a Multilayer Varistor.
Ethernet Ports
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Ethernet ports enable connection to LANs and so need medium to low energy protectors of
low capacitance.
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High speed transmission equipment encompasses a broad range of transmission protocols
such as T1/E1, ADSL, ADSL2, ADSL2+, VDSL, VDSL2, and ISDN. Transmission
equipment is located at the central office, customer premises, and remote locations.
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Transmission equipment should be protected against overvoltages that can exceed 2500 V
and surge currents up to 500 A. In the illustrations shown in Figure 6.9 through Figure 6.22,
SIDACtor® devices were chosen because their associated peak pulse current (IPP) rating is
sufficient to withstand the lightning immunity tests of GR 1089 without the additional use of
series line impedance. Likewise, the fuse shown in each of the following illustrations
(Figure 6.9 through Figure 6.22) was chosen because the amps2time (I2t) rating is sufficient
to withstand the lightning immunity tests of GR 1089, but low enough to pass GR 1089
current limiting protector test and power fault conditions (both first and second levels).
The following regulatory requirements apply:
• TIA-968-A (formerly known as FCC Part 68)
• GR 1089-CORE
• ITU-T K.20/K.21
• UL 60950
Most transmission equipment sold in the US must adhere to GR 1089. For Europe and
other regions, ITU-T K.20/K.21 is typically the recognized standard.
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Asymmetric digital subscriber lines (ADSLs) and very high speed digital subscriber lines
(VDSLs) employ transmission rates up to 30 Mbps from the Central Office Terminal (COT)
to the Remote Terminal (RT) and up to 30 Mbps from the RT to the COT. (Figure 6.9)
Central Office Site
Digital
Network
Local Loop
Remote Site
ADSL / VDSL
Transceiver Unit
ADSL / VDSL
Transceiver
Unit
ATU-C / VTU-C
ATU-R /
VTU-R
Video
Voice
Triple
Play
Data
PSTN
Figure 6.9
Splitter
POTS
ADSL Overview
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Protection Circuitry
Longitudinal protection was not used at either the ADSL / VDSL Transceiver Unit–Central
Office (ATU-C / VTU-C) interface or the ADSL / VDSL Transceiver Unit–Remote (ATU-R /
VTU-R) interface due to the absence of earth ground connections. (Figure 6.10 and
Figure 6.12) In both instances, the SL1002A350SM gas plasma arrester or the
P3500SCMC SIDACtor® device and the 04611.25 TeleLink® fuse provide metallic
protection. For xTUs not isolated from earth ground, reference the HDSL protection
topology.
04611.25
TIP
ADSL / VDSL
chip set
SL1002A350SM
RING
Figure 6.10
Gas Plasma Arrester ADSL Protection
Figure 6.11 shows the SL1002A350SM gas plasma arresters connected in the Delta
configuration to provide Tip to Ground, Ring to Ground (longitudinal), and Tip to Ring
(metallic) protection.
04611.25
SL1002A350SM
TIP
SL1002A350SM
ADSL / VDSL
chip set
RING
SL1002A350SM
04611.25
Figure 6.11
Single Port Delta Solution Providing Metallic and Longitudinal Protection
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Alternate ADSL Protection and VDSL Protection
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Protection Circuitry
The capacitance of this device is low (typically 0.8 pF) so this solution provides very low
insertion loss.
The 04611.25 fuse provides protection against power fault events, but it is specifically
designed not to open during induced lightning surges. This eliminates nuisance blowing
while maintaining the ultimate protection needed for safety.
04611.25
TIP
ADSL / VDSL
chip set
P3500SCMC
RING
Figure 6.12
SIDACtor ADSL / VDSL Protection
Component Selection
The P3500SCMC SIDACtor device and 04611.25 TeleLink fuse were chosen to protect the
ATUs because both components meet GR 1089 surge immunity requirements without the
use of additional series resistance. Although the P3100 series SIDACtor device may be
used to meet current ANSI specifications for xDSL services offered with POTS, Littelfuse
recommends the P3500 series to avoid interference with the 20 VP-P ADSL signal on a
150 V rms ringing signal superimposed on a 56.5 V battery. The VDSL signal is smaller
than a typical ADSL signal, so the P3100 may be an appropriate solution.
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HDSL (High-bit Digital Subscriber Line) is a digital line technology that uses a 1.544 Mbps
(T1 equivalent) transmission rate for distances up to 12,000 feet, eliminating the need for
repeaters. The signaling levels are a maximum of ±2.5 V while loop powering is typically
under 190 V. (Figure 6.13)
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© 2006 Littelfuse, Inc. • Telecom Design Guide
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Central Office Site
DS-1 Rate
Interface
(1.544 Mbps)
Remote Site
HDSL transceiver unit
HDSL transceiver unit
784 kbps Full-Duplex loop
HTU-C
DS-1 Rate
Interface
(1.544 Mbps)
HTU-R
784 kbps Full-Duplex loop
< 12,000 ft, 200 kHz BW
+2.5 V signal level
2B1Q, ZO=135 W
Figure 6.13
HDSL Overview
Protection Circuitry
Longitudinal protection is required at both the HDSL Transceiver Unit–Central Office (HTUC) and HDSL Transceiver Unit–Remote (HTU-R) interfaces because of the ground
connection used with loop powering. Two P2300SCMC SIDACtor devices provide
overvoltage protection, and two 04611.25 TeleLink fuses (one on Tip, one on Ring) provide
overcurrent protection. (Figure 6.14 and Figure 6.15) For the transceiver side of the
coupling transformer, additional overvoltage protection is provided by the P0080SA
SIDACtor device. The longitudinal protection on the primary coil of the transformer is an
additional design consideration for prevention of EMI coupling and ground loop issues.
4GHGTGPEG&GUKIPU
HTU-C/HTU-R Interface Protection
04611.25
Tip
P2300SCMC
P2300SCMC
P0080SAMC
TX
Ring
04611.25
Power
Sink
HDSL
Transceiver
04611.25
Tip
P2300SCMC
P2300SCMC
P0080SAMC
RX
Ring
04611.25
Figure 6.14
HDSL Protection
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HTU-C/HTU-R Interface Protection
04611.25
Tip
P0080SAMC
TX
Ring
04611.25
Power
Sink
P2304UC
HDSL
Transceiver
04611.25
Tip
P0080SAMC
RX
Ring
04611.25
Figure 6.15
HDSL Quad Protection
Component Selection
The P2304UC or P2300SCMC SIDACtor device and the 04611.25 TeleLink fuse were
chosen because both components meet GR 1089 surge immunity requirements without the
use of additional series resistance. The P2300SCMC voltage rating was selected to ensure
loop powering up to 190 V. For loop powering greater than 190 V, consider the
P2600SCMC. The P0080SAMC SIDACtor device was chosen to eliminate any sneak
voltages that may appear below the voltage rating of the P2300SCMC.
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Integrated Services Digital Network (ISDN) circuits require protection at the Network
Termination Layer 1 (NT1) U-interface and at the Terminating Equipment (TE) or
Terminating Adapter (TA) S/T interface. Signal levels at the U-interface are typically ±2.5 V;
however, with sealing currents and maintenance loop test (MLT) procedures, voltages
approaching 150 V rms can occur. (Figure 6.16)
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Terminal
Adapter
ISDN Compliant
Central Office Switching
System
T
Network
Termination
Layer 1
Terminal Equipment
(ISDN
Compliant)
B1
NT1
CO
ISDN DSL
2-Wire,
160 kbps
2B1Q ±2.5 V
TA
Non-ISDN
Terminal
POTS
T
U
Reference
B2
TE
D
B1
S
TE
T
NT2
PBX
T Reference
4-Wire
B2
D
ISDN Terminal
S
TA
S Reference, 4-Wire
Figure 6.16
ISDN Overview
Longitudinal protection was not used at either the U- or the TA/TE-interface due to the
absence of an earth-to-ground connection. (Figure 6.17) At the U-interface, the
P2600SCMC SIDACtor device and 04611.25 TeleLink fuse provide metallic protection,
while the TA/TE-interface uses the P0640SCMC SIDACtor device and 04611.25 TeleLink
fuse. Figure 6.17 also shows interfaces not isolated from earth ground.
ISDN U-Interface
ISDN S/T Interface
04611.25
04611.25
Tip
P2600SCMC
Ring
ISDN
Transceiver
ISDN
Transceiver
04611.25
RX
P0640SCMC
Power
Source
Figure 6.17
RX
P0640SCMC
TX
TX
Power
Sink
ISDN Protection
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Protection Circuitry
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Component Selection
The “SCMC” SIDACtor devices and 04611.25 TeleLink fuse were chosen because these
components meet GR 1089 surge immunity requirements without the use of additional
series resistance. An MC is chosen to reduce degradation of data rates. The P2600SCMC
voltage rating was selected to ensure coordination with MLT voltages that can approach
150 V rms. The voltage rating of the P0640SCMC was selected to ensure coordination with
varying signal voltages.
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A digital pair gain system differs from an ISDN circuit in that ring detection, ring trip, ring
forward, and off-hook detection are carried within the 64 kbps bit stream for each channel
rather than using a separate D channel. The pair gain system also uses loop powering from
10 V up to 145 V with a typical maximum current of 75 mA. (Figure 6.18)
Remote Terminal (RT)
building or pedestal
mounted
Central Office (CO)
Switching
System
MDF
Remote
Terminal
Central Office
Terminal (COT)
VF
1
VF
1
Line 1
POTS
HF
HF
VF
2
VF
2
Line 2
Customer
Premises
(CP)
POTS
Line powered
DSL 2-Wire,
160 kbps
2B1Q
Figure 6.18
Pair Gain Overview
Protection Circuitry
Longitudinal protection is required at the Central Office Terminal (COT) interface because
of the ground connection used with loop powering. (Figure 6.19) Two P1800SCMC
SIDACtor devices provide overvoltage protection, and two 04611.25 TeleLink fuses (one on
Tip, one on Ring) provide overcurrent protection. For the U-interface side of the coupling
transformer, the illustration shows the P0080SAMC SIDACtor device used for additional
overvoltage protection.
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© 2006 Littelfuse, Inc. • Telecom Design Guide
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Central Office Terminal (COT) Interface
04611.25
Tip
Tip1
P1800SCMC
Ring1
U-Interface
P0080SA
Tip2
P1800SCMC
Ring2
Ring
04611.25
Power
Source
Figure 6.19
Pair Gain COT Protection
For Customer Premises (CP) and Remote Terminal (RT) interfaces where an earth ground
connection is not used, only metallic protection is required. Figure 6.20 shows metallic
protection satisfied using a single P3100SCMC across Tip and Ring and a single 04611.25
on either Tip or Ring to satisfy metallic protection.
CPE Interface
Remote Terminal Interface
04611.25
Tip
U-Interface
Ring
04611.25
Power
Sink
Figure 6.20
P3100SCMC
Ring Detect
Ring Trip
Ring Forward
Off-Hook
Detection
4GHGTGPEG&GUKIPU
P3100SCMC
CPE
Line 1
04611.25
P3100SCMC
Line 2
Pair Gain RT Protection
Component Selection
The “SCMC” SIDACtor device and 04611.25 TeleLink fuse were chosen because both
components meet GR 1089 surge immunity requirements without the use of additional
series resistance. An MC is chosen to reduce degradation of data rates. The voltage rating
of the P1800SCMC was selected to ensure coordination with loop powering up to 150 V.
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The voltage rating of the P3100SCMC was selected to ensure coordination with POTS
ringing and battery voltages.
7(-&LUFXLW3URWHFWLRQ
T1/E1 networks offer data rates up to 1.544 Mbps (2.058 for E1) on four-wire systems.
Signal levels on the transmit (TX) pair are typically between 2.4 V and 3.6 V while the
receive (RX) pair could go as high as 12 V. Loop powering is typically ±130 V at 60 mA,
although some systems can go as high as 150 V. (Figure 6.21)
Central Office
Line Regenerator
Line Regenerator
T1 Transceiver
3000 ft
6000 ft
TX Pair
RX Pair
Line powered DLC Four-wire,1.544 Mbps / 2.048 Mbps
Figure 6.21
T1/E1 Overview
Protection Circuitry
Longitudinal protection is required at the Central Office Terminal (COT) interface because
of the ground connection used with loop powering. (Figure 6.22, Figure 6.23, Figure 6.24)
Two P1800SCMC (or P1804UC or P2106UC) SIDACtor devices provide overvoltage
protection, and two 04611.25 TeleLink fuses (one on Tip, one on Ring) provide overcurrent
protection. The P1800SCMC device is chosen because its V drm is compliant with
TIA-968-A regulations, Section 4.4.5.2, “Connections with protection paths to ground.”
These regulations state:
Approved terminal equipment and protective circuitry having an
intentional dc conducting path to earth ground for protection purposes at
the leakage current test voltage that was removed during the leakage
current test of section 4.3 shall, upon its replacement, have a 50 Hz or
60 Hz voltage source applied between the following points:
a. Simplexed telephone connections, including Tip and Ring, Tip-1
and Ring-1, E&M leads and auxiliary leads
b. Earth grounding connections
The voltage shall be gradually increased from zero to 120 V rms for approved
terminal equipment, or 300 V rms for protective circuitry, then maintained for one
minute. The current between a. and b. shall not exceed 10 mAPK at any time. As
an alternative to carrying out this test on the complete equipment or device, the
test may be carried out separately on components, subassemblies, and simulated
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circuits, outside the unit, provided that the test results would be representative of
the results of testing the complete unit.
Regenerator
COT
04611.25
04611.25
P1800SCMC
P0640SCMC
TX P0300SAMC
RX
P1800SCMC
04611.25
T1
Transceiver
T1
Transceiver
Power
Source
04611.25
04611.25
P1800SCMC
RX P0300SAMC
P0640SCMC
TX
P1800SCMC
04611.25
T1/E1 Protection
COT
Regenerator
04611.25
TX
P0080SAMC
04611.25
P0640SCMC
4GHGTGPEG&GUKIPU
Figure 6.22
RX
04611.25
T1
Transceiver
Power
Source
T1
Transceiver
P1804UC
04611.25
04611.25
RX
P0080SAMC
P0640SCMC
TX
04611.25
Figure 6.23
T1/E1 Quad Protection
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COT
Regenerator
04611.25
TX P0080SAMC
04611.25
P0640SCMC
RX
04611.25
2
+130 V
T1
Transceiver
Power
Source
–130 V
1
3
4
6
T1
Transceiver
P2106UC
04611.25
5
04611.25
RX P0080SAMC
P0640SCMC
TX
04611.25
Figure 6.24
T1/E1 Symmetrical Protection
The peak voltage for 120 V rms is 169.7 V. The minimum stand-off voltage for the P1800
(or P1804 and P2106) is 170 V, therefore, the P1800SCMC will pass the test in
Section 4.4.5.2 by not allowing 10 mA of current to flow during the application of this test
voltage.
For the transceiver side of the coupling transformer, additional overvoltage protection is
shown in Figure 6.22 using the P0300SA SIDACtor device. When an earth ground
connection is not used, only metallic protection is required. Metallic protection is satisfied
using a single P0640SCMC SIDACtor device across Tip and Ring and a single 04611.25
TeleLink fuse on either Tip or Ring.
Component Selection
The “SCMC” SIDACtor device and 04611.25 TeleLink fuse were chosen because these
components meet GR 1089 surge immunity requirements without the use of additional
series resistance. An MC is chosen to reduce degradation of data rates. The voltage rating
of the P1800SCMC (or P1804UC or P2106UC) was selected to ensure loop powering up to
150 V. The voltage rating of the P0640SCMC was selected to ensure coordination with
varying voltage signals.
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7(-$V\PPHWULFDO&LUFXLW3URWHFWLRQ
The A2106UC6 Surface Mount SIDACtor device provides asymmetrical protection for
T1/E1/J1 transceivers. (Figure 6.25) Metallic events are limited to less than 80 V on the line
side of the transformer. The minimum turn on voltage for the A2106 is 170 V from Tip to
Ground and Ring to Ground. This is compliant with TIA-968-A. The secondary side of the
transformer has the P0080SAMC SIDACtor device that limits differential voltages to less
than 25 V.
T1 Transceiver
04611.25
TX
P0080SAMC
04611.25
2
+130 V
Loop Current
Power Source
1
3
4
6
A2106UC6
-130 V
5
04611.25
P0080SAMC
RX
Figure 6.25
T1/E1/J1 Asymmetrical Protection
Protection Circuitry
The T1/E1 transceiver circuit is protected from AC power fault events (also known as over
current events) by the 04611.25 TeleLink fuses. The TeleLink fuses in combination with the
SIDACtor devices are compliant with the requirements of GR 1089, TIA-968-A, and
UL 60950.
$GGLWLRQDO7'HVLJQ&RQVLGHUDWLRQV
A T1 application can be TIA-968-A approved as two different possible device types. An
XD device means an external CSU is used, and while the unit does not have to meet the
TIA-968-A environmental test conditions, it must connect only behind a separately
registered DE device. This XD equipment does not have to meet the T1 pulse template
requirements. If not classified as an XD device, then typically the application must adhere to
TIA-968-A environmental test conditions.
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04611.25
+LJK6SHHG7UDQVPLVVLRQ(TXLSPHQW
73URWHFWLRQ
The SL1002A090 in combination with the TeleLink fuse (Figure 6.26) is one low off-state
capacitance solution. Figure 6.27 shows an alternate solution. The capacitance across the
pair of wires = (D1 || D2) + P0640EC/SC. The diode capacitance is approximately (10 pF ||
10 pF) 20 pF. Then adding the capacitive effect of the P0640EC/SCMC, which is typically
60 pF, the total capacitance across the pair of wires is approximately 15 pF. The MUR
1100E diodes are fast-switching diodes that will exhibit this level of capacitance.
MURS160T3 is a surface mount equivalent. (Figure 6.27)
04611.25
SL1002A090
Figure 6.26
T3 Protection—Gas Plasma Arrester
04611.25
D1
D2
P0640EC/SCMC or
P0720EC/SCMC
Figure 6.27
T3 Protection—SIDACtor Device and Diodes
Alternately, the advanced P0642SA exhibits very low capacitance and can be used as a
stand-alone device. (Figure 6.28)
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+LJK6SHHG7UDQVPLVVLRQ(TXLSPHQW
0461.500
P0642SA
Figure 6.28
T3 Protection—SIDACtor Device
&RRUGLQDWLRQ&RQVLGHUDWLRQV
Coordination between the primary protection and the secondary protection may require the
addition of a resistor. (Figure 6.29)
Secondary Protection
04611.25
Figure 6.29
4GHGTGPEG&GUKIPU
04611.25
Coordination Solution with Resistor
The coordinating resistor value depends on:
• Distance between the primary and secondary protector
• Turn-on characteristics of the primary and secondary protector
• Surge rating of the secondary protector
For compliance with the GR 1089 requirement, the additional component is not required
IF the peak pulse surge rating of the secondary protector is at least 100 A for a 10x1000
event. The ITU recommendations have an alternative solution as well, depending on
whether Basic or Enhanced compliance is desired.
For Basic compliance, if the secondary protector has a peak pulse surge rating of at least
1000 A for an 8x20 event, then the additional component is not required. For the Enhanced
level, it must be able to withstand a 5000 A for an 8x20 event. Otherwise, a coordinating
component is required. This component allows the primary protector to turn on during surge
events even though the secondary protector may turn on first. The power rating of this
resistor can be reduced by including the TeleLink overcurrent protection device. However, it
must not open during the surge events. Typically, a 1-3 W resistor will be sufficient.
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$QDORJ/LQH&DUGV
Given that line cards are highly susceptible to transient voltages, network hazards such as
lightning and power fault conditions pose a serious threat to equipment deployed at the
central office and in remote switching locations. To minimize this threat, adequate levels of
protection must be incorporated to ensure reliable operation and regulatory compliance.
3URWHFWLRQ5HTXLUHPHQWV
When designing overvoltage protection for analog line cards, it is often necessary to
provide both on-hook (relay) and off-hook (SLIC) protection. This can be accomplished in
two stages, as shown in Figure 6.30.
04611.25
On-hook
Protection
R
E
L
A
Y
Off-hook
Protection
S
L
I
C
04611.25
Figure 6.30
SLIC Overview
The following regulatory requirements may apply:
• GR 1089-CORE
• ITU-T K.20/K.21
• UL 60950
• TIA-968-A (formerly known as FCC Part 68)
2Q+RRN5HOD\3URWHFWLRQ
On-hook protection is accomplished by choosing a SIDACtor® device that meets the
following criteria to ensure proper coordination between the ring voltage and the maximum
voltage rating of the relay to be protected.
VDRM > VBATT + VRING
VS ≤ VRelay Breakdown
This criterion is typically accomplished using two P2600S_ SIDACtor devices (where
_ denotes the surge current rating) connected from Tip to Ground and Ring to Ground.
However, for applications using relays such as an LCAS (Line Card Access Switch),
consider the P1200S_ from Tip to Ground and the P2000S_ from Ring to Ground.
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2II+RRN6/,&3URWHFWLRQ
Off-hook protection is accomplished by choosing a SIDACtor device that meets the
following criteria to ensure proper coordination between the supply voltage (VREF) and the
maximum voltage rating of the SLIC to be protected.
VDRM > VREF
VS ≤ VSLIC Breakdown
This criterion can be accomplished in a variety of ways. Applications using an external
ringing generator and a fixed battery voltage can be protected with a single P0641CA2 or
two P0641SA SIDACtor devices or with any of the following, depending on the actual value
of the battery reference voltage:
•
•
•
•
•
P0721UA or two P0721CA2 or four P0721SA
P0901UA or two P0901CA2 or four P0901SA
P1101UA or two P1101CA2 or four P1101SA
P1301UA or two P1301CA2 or four P1301SA
P1701UA or two P1701CA2 or four P1701SA
Use the SC version for applications complying to GR 1089 inter-building or ITU K20/21
Enhanced Recommendations. For ring-generating SLIC chipsets, the Battrax® protector
(B1xxx 6-pin devices) can be used.
The IPP of the SIDACtor device must be greater than or equal to the maximum available
surge current (IPK(available)) of the applicable regulatory requirements. Calculate the maximum
available surge current by dividing the peak surge voltage supplied by the voltage generator
(VPK) by the total circuit resistance (RTOTAL). The total circuit resistance is determined by
adding the source resistance (RS) of the surge generator to the series resistance in front of
the SIDACtor device on Tip and Ring (RTIP and RRING).
IPP ≥ IPK(available)
IPK(available) = VPK / RTOTAL
For metallic surges:
RTOTAL = RS + RTIP + RRING
For longitudinal surges:
RTOTAL = RS + RTIP
RTOTAL = RS + RRING
5HIHUHQFH'LDJUDPV
Littelfuse offers a wide variety of protection solutions for SLIC applications. Some nonringing SLIC applications require an asymmetrical type of protection, while others require a
balanced protection solution. The ringing SLIC applications can be protected with fixed
voltage SIDACtor devices or with programmable Battrax devices. Figure 6.31 through
Figure 6.53 illustrate these many different solutions. The TeleLink fuse is also included in
these illustrations so that GR 1089-compliant overvoltage and overcurrent protection is
provided.
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4GHGTGPEG&GUKIPU
, 6HOHFWLRQ
$QDORJ/LQH&DUGV
LCAS
Relay
04611.25
SLIC
Tip
P0641SC
A1220UC
P0641SC
Ring
04611.25
Figure 6.31
SLIC Protection for LCAS
LCAS
Relay
LFR *
SLIC
Tip
-Vbat
A1220UA
0.2 μF
Teccor
B1101UA
LFR *
Ring
* Assumed minimum resistance of 20 Ω. If the LFR does not have a fusible link,
then the 04611.25 is recommended for overcurrent protection.
Figure 6.32
SLIC Protection with Limiting Resistance
LCAS
Relay
LFR *
SLIC
Tip
-Vbat
A1220UA
0.2 μF
Teccor
BNxxxx_
LFR *
Ring
* Assumed minimum resistance of 20 Ω. If the LFR does not have a fusible link,
then the 04611.25 is recommended for overcurrent protection.
Figure 6.33
SLIC Protection with Limiting Resistance—Buffered Battrax
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© 2006 Littelfuse, Inc. • Telecom Design Guide
$QDORJ/LQH&DUGV
LCAS
RELAY
LFR *
SLIC
Tip
-Vbat
P1200SA
0.2 μF
LFR *
Teccor
B1101UA4
P2000SA
Ring
One quad package
protects two ports.
LCAS
RELAY
LFR *
SLIC
Tip
P1200SA
LFR *
P2000SA
Ring
Figure 6.34
4GHGTGPEG&GUKIPU
* Assumed minimum resistance of 20 Ω. If the LFR does not have a fusible link,
then the 04611.25 is recommended for overcurrent protection.
SLIC Protection with Quad Battrax
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$QDORJ/LQH&DUGV
LCAS
RELAY
LFR *
SLIC
Tip
LFR *
Ring
2
-Vbat
1
3
B1101UA4
A1220UA
0.2 μF
4
One quad package
protects two ports.
6
LCAS
RELAY
LFR *
SLIC
5
Tip
LFR *
Ring
* Assumed minimum resistance of 20 Ω. If the LFR does not have a fusible link,
then the 04611.25 is recommended for overcurrent protection.
Figure 6.35
SLIC Protection with Quad Battrax and Balanced Relay Protector
LCAS
RELAY
04611.25
P605 P0720SC
SLIC
Tip
P1200SC
110 72
72 110
P2000SC
Ring
04611.25
Figure 6.36
P605 P0720SC
SLIC Protection with Asymmetrical Devices
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$QDORJ/LQH&DUGV
LCAS
RELAY
04611.25
SLIC
Tip
-Vbat
P1200SC
B1101UC
0.2 μF
P2000SC
Ring
04611.25
Figure 6.37
SLIC Protection with Battrax
LCAS
RELAY
04611.25
SLIC
Tip
P1200SC
P2000SC
Ring
04611.25
B1101UC4
0.2 μF
LCAS
RELAY
04611.25
One quad package
protects two ports.
SLIC
Tip
P1200SC
P2000SC
Ring
04611.25
Figure 6.38
SLIC Protection with Quad Battrax with Asymmetrical Relay Protection
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4GHGTGPEG&GUKIPU
-Vbat
$QDORJ/LQH&DUGV
Figure 6.39 illustrates uses of asymmetrical SIDACtor protection for overvoltage conditions
and the 04611.25 for overcurrent conditions.
RELAY
04611.25
SLIC
Tip
P1200SC
P2500SC
P2500SC
Ring
04611.25
Figure 6.39
SLIC Asymmetrical Protection
Figure 6.40 illustrates the use of the P2600SA and P0721CA2 for overvoltage protection
and the 0461.500 for overcurrent protection in addition to 20 Ω of series resistance on both
Tip and Ring. The series resistance is required to limit the transient surge currents to within
the surge current rating of the “A” series SIDACtor devices and the 0461.500 TeleLink®
fuse.
20 Ω
0461.500
RELAY
SLIC
P0721CA2
Tip
P2600SA
P2600SA
Ring
20 Ω
Figure 6.40
0461.500
SLIC Protection with Fixed Voltage SIDACtor Devices
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Figure 6.41, Figure 6.42, and Figure 6.43 illustrate the use of different circuits to coordinate
overvoltage and overcurrent protection when protecting the LCAS family of solid state
switches. Figure 6.41 illustrates the use of the TeleLink and the SIDACtor. The TeleLink is
a surface mount, surge resistant fuse that saves cost and PCB real estate over more
traditional solutions.
04611.25
LCAS
RELAY
SLIC
Tip
P0641CA2
Ring
04611.25
A1220UC4
04611.25
One quad package
protects two ports.
LCAS
RELAY
SLIC
Tip
4GHGTGPEG&GUKIPU
P0641CA2
Ring
04611.25
Figure 6.41
SLIC Protection with TeleLink Multiport
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Figure 6.42 illustrates the use of a line feed resistor with a thermal link and the SIDACtor.
The advantage of using an LFR is that it attenuates surge currents, allowing use of a
SIDACtor with a lower surge current rating.
LCAS
RELAY
LFR *
SLIC
Tip
P0641CA2
LFR *
Ring
A1220UA4
One quad package
protects two ports.
LCAS
RELAY
LFR *
SLIC
Tip
P0641CA2
LFR *
Ring
* Assumed minimum resistance of 20 Ω. If the LFR does not have a fusible link,
then the 04611.25 is recommended for overcurrent protection.
Figure 6.42
SLIC Protection with LFR Multiport
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Figure 6.43 illustrates a single port version with the TeleLink and discrete SIDACtors.
LCAS
RELAY
04611.25
SLIC
Tip
P1200SC
P0641CA2
P1200SC
Ring
04611.25
Figure 6.43
SLIC Protection with Single Port Discrete
20 Ω
-VREF
LCAS
RELAY
0461.500
0.2 μF
SLIC
Tip
P3100SA
EDF1BS
B1100CC
P3100SA
Ring
20 Ω
Figure 6.44
0461.500
SLIC Protection with a Single Battrax Device
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4GHGTGPEG&GUKIPU
Figure 6.44 shows protection of a SLIC using 20 Ω series resistors on both Tip and Ring in
addition to Littelfuse’s Battrax (B1100CC) and a diode bridge (General Semiconductor part
number EDF1BS). However, the overshoot caused by the diode bridge must be
considered. The series resistance (a minimum of 20 Ω on Tip and 20 Ω on Ring) limits the
simultaneous surge currents of 100 A from Tip to Ground and 100 A from Ring to Ground
(200 A total) to within the surge current rating of the SA-rated SIDACtor device and Battrax.
The diode bridge shunts all positive voltages to Ground, and the B1100CC shunts all
negative voltages greater than |-VREF -1.2 V| to Ground.
$QDORJ/LQH&DUGV
In Figure 6.45 and Figure 6.46 an application that requires 50 Ω Line Feed Resistors (LFR)
uses one B1160CC and two EDF1BS diode bridges in place of multiple SLIC protectors.
The overshoot caused by the diode bridge must be considered; however, with this
approach it is imperative that the sum of the loop currents does not exceed the Battrax’s
holding current. In the application shown in Figure 6.45 and Figure 6.46, each loop current
would have to be limited to 80 mA. For applications requiring the protection of four twisted
pair with one Battrax, use the B1200CC and limit each individual loop current to 50 mA.
50 Ω LFR
RELAY
SLIC
Tip
P3100SA
EDF1BS
P3100SA
Ring
50 Ω LFR
B1160CC
-VREF
50 Ω LFR
RELAY
SLIC
0.2 μF
Tip
P3100SA
EDF1BS
P3100SA
Ring
50 Ω LFR
Figure 6.45
SLIC Protection with a Single Battrax Device
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© 2006 Littelfuse, Inc. • Telecom Design Guide
$QDORJ/LQH&DUGV
50 Ω LFR
RELAY
SLIC
Tip
EDF1BS
Ring
50 Ω LFR
B1160CC
P3104UA
50 Ω LFR
-VREF
RELAY
SLIC
0.2 μF
Tip
EDF1BS
4GHGTGPEG&GUKIPU
Ring
50 Ω LFR
Figure 6.46
SLIC Protection with Diode Bridge
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Figure 6.47, Figure 6.48, and Figure 6.49 show circuits that use negative Battrax devices
containing an internal diode for positive surge protection. This obviates using the discrete
diodes shown in Figure 6.44, Figure 6.45, and Figure 6.46.
-VREF
04611.25
SLIC
T
B1xx1UC
0.2 μF
04611.25
R
Figure 6.47
SLIC Protection with a Dual Battrax Device
SLIC
04611.25
T1
04611.25
R1
-VREF
B1xx1UC4
6
4
5
2
0.2 μF
1
3
SLIC
04611.25
T2
04611.25
R2
Figure 6.48
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SLIC Protection with a Single Battrax Quad Negative Device
6 - 36
© 2006 Littelfuse, Inc. • Telecom Design Guide
$QDORJ/LQH&DUGV
0.2 μF
+VREF
-VREF
0.2 μF
04611.25
SLIC
Tip
B3104UC
Ring
04611.25
-VREF
+VREF
Figure 6.49
SLIC Protection with a Battrax Dual Positive/Negative Device
Figure 6.50 shows a SLIC application protected by the BN1718C Battrax device and two
TeleLink fuses. This surface mount arrangement provides a minimum footprint solution for
both overcurrent and overvoltage protection. The BN1718C Battrax protects against both
positive and negative induced surge events. The integrated diode within this package
provides the positive polarity protection.
4GHGTGPEG&GUKIPU
SLIC
04611.25
Tip
1,8
BN1728C
-VBATT
2
(-VREF)
6,7
0.2 μF
4,5
Ring
04611.25
Figure 6.50
SLIC Protection with an 8-pin Battrax Dual Positive/Negative Device
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6/,&3URWHFWLRQ2SWLRQV
Figure 6.51 through Figure 6.54 illustrate SLIC protection options.
04611.25
SLIC
Tip
Ring
04611.25
-Vbat
B1101UC4
0.2 μF
One quad package
protects two ports.
SLIC
04611.25
Tip
Ring
04611.25
Figure 6.51
SLIC Protection with Quad Battrax
LFR *
SLIC
Tip
-Vbat
B1101UA
0.2 μF
LFR *
Ring
* Assumed minimum resistance of 20 Ω. If the LFR
does not have a fusible link, then the 04611.25
is recommended for overcurrent protection.
Figure 6.52
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SLIC Protection with Series R and Battrax
6 - 38
© 2006 Littelfuse, Inc. • Telecom Design Guide
$QDORJ/LQH&DUGV
SLIC
LFR *
Tip
1,8
BN1728F
-VBATT
2
(-VREF)
6,7
0.2 μF
LFR *
4,5
Ring
* Assumed minimum resistance of 20 Ω. If the LFR
does not have a fusible link, then the 04611.25
is recommended for overcurrent protection.
SLIC Protection with Series R and 8-pin Battrax
4GHGTGPEG&GUKIPU
Figure 6.53
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$QDORJ/LQH&DUGV
LFR *
SLIC
Tip
-Vbat
0.2 μF
Teccor
B1101UA4
LFR *
Ring
One quad package
protects two ports.
LFR *
SLIC
Tip
LFR *
Ring
* Assumed minimum resistance of 20 Ω. If the LFR
does not have a fusible link, then the 04611.25
is recommended for overcurrent protection.
Figure 6.54
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SLIC Protection with Series R and Quad Battrax
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Many SLIC card designs do not require the Battrax protection gate buffer circuit shown in
Figure 6.55. This circuit is useful to improve the voltage overshoot performance during AC
power fault events. There is no impact on lightning surge performance as the gate capacitor
is the only current source required during high dv/dt events.
04611.25
-VREF
SLIC
T
B1xx1UC
D
0.2 μF
Q
R
iq
– Vbias
+
R
04611.25
Battrax Protection Gate Buffer Circuit
During slower events (such as power fault), the current from the capacitor (C x dv/dt) may
not source the needed current (100 mA max) to gate the SCR on. This does not apply to the
BNxxxx series as its gate trigger valve is 5 mA. Under these conditions, this buffer circuit
will source the needed current. The SLIC card bias supply is a negative (sinking) supply
and cannot source any current.
In many designs, the bias supply is also the main supply powering the SLIC card. As such,
the supply has a significant load at all times. This is the source of the gate current. When
sourcing the gate current, the bias supply is actually being relieved of the load. As long as
the load on the bias supply is 100 mA for each line protected, this buffer circuit is not
needed. For lightly loaded bias supplies, this circuit may be useful.
Protection Circuitry
The buffer circuit consists of a diode, a resistor, and a transistor connected as shown. A
small current iq circulates constantly from the supply through the resistor and diode. When
required to source current (during a fault condition where the emitter is being pulled more
negative than the Vbias supply), the transistor Q will turn on because iq is available as base
current and Q will provide the needed current from its collector, out the emitter and into the
gate of the Battrax device. One buffer circuit may provide current to several Battrax devices
if properly designed.
Component Selection
Transistor Q should be selected to have a collector breakdown voltage well in excess of the
bias supply voltage. The current available from Q will be Hfe x Vbias / R where Hfe is the gain
Telecom Design Guide • © 2006 Littelfuse, Inc.
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Figure 6.55
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of the transistor. The current available should be at least 100 mA per line protected.
Selection of a Darlington pair transistor with a large gain can greatly increase the allowed
value of R, reducing the quiescent dissipation.
The diode D need only be a small signal diode and may not be needed if the supply has its
own source current protection built in.
The resistor R should be selected by the equation above to yield the needed source
current. Keep in mind that it will dissipate Vbias2 / R and should be sized appropriately. If
there is ANY constant load on the Vbias supply due to the SLIC card design, the equivalent
resistance of that load may be lumped into the R calculation and, in many cases, make R
unnecessary.
This buffer circuit is not required for the new BNxxxx series Battrax devices. The internal
structure of this device accomplishes the function of this darlington pair circuit.
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© 2006 Littelfuse, Inc. • Telecom Design Guide
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PBXs, KSUs, and PABXs contain line cards that support various transmission protocols
such as ISDN, T1/E1, HDSL, and ADSL (Figure 6.56). PBXs also have features such as a
POTS (plain old telephone service) pull-through which allows stations to have outside line
access in the event of power failure. All incoming lines to the PBX are subject to
environmental hazards such as lightning and power fault.
Station Primary
Protection
Logic
Stations
POTS
T1/E1
ADSL
HDSL
ISDN
PBX Overview
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Branch exchange switches should be protected against overvoltages that can exceed
800 V and surge currents up to 100 A.
The following regulatory requirements apply:
• TIA-968-A (formerly known as FCC Part 68)
• UL 60950
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Refer to the following for information on interface circuits used to protect of PBX line cards:
• For POTS protection, see "Customer Premises Equipment (CPE)" on page 6-2.
• For ADSL protection, see "ADSL / VDSL Circuit Protection" on page 6-10.
• For HDSL protection, see "HDSL Circuit Protection" on page 6-12.
• For ISDN protection, see "ISDN Circuit Protection" on page 6-14.
• For T1/E1 protection, see "T1/E1/J1 Circuit Protection" on page 6-18.
• For Station Protection, see "Analog Line Cards" on page 6-24.
Telecom Design Guide • © 2006 Littelfuse, Inc.
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PBX
Figure 6.56
Line Cards
Station
Cards
Matrix
Switch
Station
Cards
To Network
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As cable providers enter the local exchange market, protection of CATV (Community
Antenna TV) equipment becomes even more critical in order to ensure reliable operation of
equipment and uninterrupted service.
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CATV line equipment should be able to withstand overvoltages that exceed 6000 V and
surge currents up to 5000 A. CATV station protectors should be able to withstand
overvoltages that exceed 5000 V and surge currents up to 1000 A. The SIDACtor® devices
illustrated in Figure 6.57 through Figure 6.61 meet these requirements.
The following regulatory requirements may apply:
• UL 497C
• SCTE IPS-SP-204
• SCTE Practices
• NEC Article 830
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Figure 6.57 and Figure 6.59 show how the P1900ME SIDACtor device is used to protect
line amplifiers and power supplies versus using two SCRs and one SIDACtor device, as
shown in Figure 6.60. The P1900ME is used because the peak off-state voltage (VDRM) is
well above the peak voltage of the CATV power supply (90 VRMS √2), and the peak pulse
current rating (IPP) is 3000 A.
CATV
Amplifiers
90 VAC
Power
Supply
P1900ME
Figure 6.57
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CATV Amplifier Diagram
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The circuits shown in Figure 6.58, Figure 6.59, and Figure 6.60 may be covered by one or
more patents.
90 VAC RF
To Line
Amplifiers
SL1002A090
Power
Port
Figure 6.58
Note: Isolating inductor
may not be required.
Gas Plasma Arrester CATV Amplifier Protection (incorporated into a power inserter
module)
90 VAC RF
To Line
Amplifiers
P1900ME
Figure 6.59
SIDACtor CATV Amplifier Protection (incorporated into a power inserter module)
90 VAC RF
K
To Line
Amplifiers
A
G
P1800EC
G
A
Figure 6.60
K
CATV Amplifier Protection
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Power
Port
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Figure 6.61 shows a P1400AD SIDACtor device used in a CATV station protection
application. Note that a compensation inductor may be required to meet insertion and
reflection loss requirements for CATV networks. If so, the inductor should be designed to
saturate quickly and withstand surges up to 200 V and 1000 A. An inductor with a core
permeability of approximately 900 Wb/A·m and wound with 24-gauge wire to an inductance
of 20 μH to 30 μH is an example of a suitable starting point, but the actual value depends
on the design and must be verified through laboratory testing.
Figure 6.62 is a protection circuit that does not require the compensating inductor.
UL Approved
Coaxial Fuse Line
Compensating
Inductor
To Protected
Equipment
P1400AD
Figure 6.61
SIDACtor CATV Station Protection
To Protected
Equipment
UL Approved
Coaxial Fuse Line
SL1002A 350
Figure 6.62
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Gas Plasma Arrester CATV Station Protection
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© 2006 Littelfuse, Inc. • Telecom Design Guide
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Primary telecommunications protectors must be deployed at points where exposed twisted
pairs enter an office building or residence. This requirement is mandated in North America
by the National Electric Code (NEC) to protect end users from the hazards associated with
lightning and power fault conditions.
Primary protection is provided by the local exchange carrier and can be segregated into
three distinct categories:
• Station protection—typically associated with a single twisted pair
• Building entrance protection—typically associated with multiple (25 or more) twisted pair
• Central office protection—typically associated with numerous twisted pair feeding into a
switch
Station protectors provide primary protection for a single-dwelling residence or office. The
station protector is located at the Network Interface Unit (NIU), which acts as the point of
demarcation, separating the operating company’s lines from the customer’s.
Building entrance protection is accomplished by installing a multi-line distribution panel with
integrated overvoltage protection. These panels are normally located where multiple twisted
pairs enter a building.
A five-pin protection module plugged into a Main Distribution Frame (MDF) provides Central
and Remote Office protection. Like station and building entrance protection, the MDF is
located where exposed cables enter the switching office.
Littelfuse offers components used in five-pin protectors. For further details, contact factory.
Station protectors must be able to withstand 300 A 10x1000 surge events. The building
entrance protectors and CO protectors must be able to withstand 100 A 10x1000 surge
events. Figure 6.64 shows building entrance protector and CO protector asymmetrical
solutions. Figure 6.66 shows building entrance protector and CO protector balanced
solutions.
The following regulatory requirements apply:
• UL 497
• GR 974-CORE
• ITU K.28
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Figure 6.63 through Figure 6.66 show different configurations used in primary protection.
Note that the peak off-state voltage (VDRM) of any device intended for use in primary
protection applications should be greater than the potential of a Type B ringer
superimposed on a POTS (plain old telephone service) battery.
150 VRMS √2 + 56.6 VPK = 268.8 VPK
Telecom Design Guide • © 2006 Littelfuse, Inc.
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Thermal
Overload
SL1002A250
Voltage-only
Protection
Voltage and
Sneak Current
Protection
SL1002A250
4 W Heat Coil
Figure 6.63
Gas Plasma Arrester Primary Protection
Thermal
Overload
P6002AC
or
P6002AD
P6002AC
or
P6002AD
Voltage-only
Protection
Voltage and
Sneak Current
Protection
4 W Heat Coil
Figure 6.64
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SIDACtor Primary Protection
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© 2006 Littelfuse, Inc. • Telecom Design Guide
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Thermal
Overload
T10CL270E
Voltage-only
Protection
Voltage and
Sneak Current
Protection
T10CL270E
4 W Heat Coil
SIDACtor Cell Primary Protection
Thermal
Overload
P3203AC
Voltage-only
Protection
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Figure 6.65
Voltage and
Sneak Current
Protection
P3203AC
4 W Heat Coil
Figure 6.66
Balanced SIDACtor Primary Protection
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Secondary protectors (stand alone units or integrated into strip protectors and UPSs) are
adjunct devices used to enhance the protection level of customer premise equipment
(CPE). Due to the inadequate level of protection designed into CPE, secondary protectors
often are required to prevent premature failure of equipment exposed to environmental
hazards. (Figure 6.67)
Telephone
Network
Primary
Protector
Tip
Customer
Premise Equipment
Line
Impedance
P
S
Ring
Fax/Modem
Network
Interface
Figure 6.67
Phone
Secondary
Protector
CPE Secondary Protection
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Secondary protectors should be able to withstand overvoltages that can exceed 800 V and
surge currents up to 100 A. Figure 6.68 illustrates a SIDACtor® device selected because
the associated peak pulse current (IPP) is sufficient to withstand the lightning immunity tests
of TIA-968-A (formerly known as FCC Part 68) without the additional use of series line
impedance. Likewise, Figure 6.68 illustrates a fuse selected because the amps2time (I2t)
rating is sufficient to withstand the lightning immunity tests of TIA-968-A, but low enough to
pass UL power fault conditions.
04611.25
Tip
P3203AB
or
P3203AC
To CPE
Equipment
Ring
04611.25
Figure 6.68
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CPE Protection
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© 2006 Littelfuse, Inc. • Telecom Design Guide
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Figure 6.67 also shows an example of an interface design for a secondary protector. The
P3203AB SIDACtor device is used because the peak off-state voltage (VDRM) is greater
than the potential of a Type B ringer signal superimposed on the POTS (plain old telephone
service) battery.
150 VRMS √2 + 56.6 VPK = 268.8 VPK
4GHGTGPEG&GUKIPU
Coordination between the station protector and the secondary protector occurs due to the
line impedance between the two devices. The line impedance helps ensure that the primary
protector will begin to conduct while the secondary protector limits any of the let-through
voltage to within the VS rating of the SIDACtor device.
Telecom Design Guide • © 2006 Littelfuse, Inc.
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Damage can occur to a thyristor if the thyristor’s repetitive peak off-state voltage is
exceeded. A thyristor’s repetitive peak off-state voltage may be exceeded due to dirty
AC power mains, inductive spikes, motor latch up, and so on.
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Figure 6.69 and Figure 6.70 show two different methods of protecting a triac. In Figure 6.69
a SIDACtor® device is connected from MT2 to the gate of the triac. When the voltage
applied to the triac exceeds the SIDACtor device’s VDRM, the SIDACtor device turns on,
producing a gate current which turns the triac on.
Load
47 Ω
Hot
MT2
Triac
SIDACtor
To
Gating
Circuitry
MT1
Neutral
Figure 6.69
Triac Protection
The circuit in Figure 6.70 places a SIDACtor device across MT2 and MT1 of the triac. In this
instance the SIDACtor device protects the triac by turning on and shunting the transient
before it exceeds the VDRM rating of the triac.
Load
Hot
MT2
Triac
To
Gating
Circuitry
SIDACtor
MT1
Neutral
Figure 6.70
Triac Protection
With both methods, consider the following designs when using a SIDACtor device to protect
a thyristor:
• VDRM of the SIDACtor device < VDRM of Triac
• SIDACtor device VDRM > 120% VPK(power supply)
• SIDACtor device must be placed behind the load
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© 2006 Littelfuse, Inc. • Telecom Design Guide
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In many office and industrial locations, data lines (such as RS-232 and ethernet) and
AC power lines run in close proximity to each other, which often results in voltage spikes
being induced onto the data line, causing damage to sensitive equipment.
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Data lines should be protected against overvoltages that can exceed 1500 V and surge
currents up to 50 A.
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Figure 6.71 shows how a SIDACtor device is used to protect low voltage data line circuits.
TXD
P0080SAMC
or
P0300SAMC
RXD
P0080SAMC
or
P0300SAMC
RS-232
I.C.
4GHGTGPEG&GUKIPU
CTS
P0080SAMC
or
P0300SAMC
Figure 6.71
Data Line Protection
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Capacitance across the pair of wires = (D1 || D2) + P0640EA/SA
The MUR 1100E diodes capacitance is approximately (10 pF || 10 pF) 20 pF. Then, adding
the capacitive effect of the SIDACtor (typically 35 pF), the total capacitance across the pair
of wires is approximately 14 pF. This provides a GR 1089 intra-building compliant design.
(Figure 6.72)
Note: MURS160T3 is an SMT equivalent of the MUR 1100E.
Figure 6.73 shows an application requiring longitudinal protection.
0461.500
D1
D2
P0300SA MC
Figure 6.72
10Base-T Metallic-only Protection
0461.500
D1
D2
P0300SA MC
P0300SA MC
0461.500
Figure 6.73
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D4
10Base-T Metallic and Longitudinal Protection
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Capacitance across the pair of wires = (D1 || D2) + P0640EA/SA + (D3 || D4)
The MUR 1100E pair of diodes capacitance is approximately (10 pF || 10 pF) 20 pF. Then,
adding the capacitive effect of the P0300SA MC (typically 35pF), the total capacitance
across the pair of wires is approximately 8 pF. This will provide a GR 1089 intra-building
compliant design. (Figure 6.74)
Note: MURS160T3 is a SMT equivalent of the MUR 1100E.
The P0642SA is a very low capacitance device that requires no compensating diodes.
(Figure 6.75)
0461.500
D1
D2
P0300SA MC
D3
100 Base-T Protection
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Figure 6.74
D4
0461.500
P0642SA
Figure 6.75
100 Base-T Protection Without External Compensation
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