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. Telecom Design Guide • © 2006 Littelfuse, Inc. 6-1 www.littelfuse.com 4GHGTGPEG&GUKIPU 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. &XVWRPHU3UHPLVHV(TXLSPHQW&3( &XVWRPHU3UHPLVHV(TXLSPHQW&3( 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. 3URWHFWLRQ5HTXLUHPHQWV 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. &3(5HIHUHQFH&LUFXLWV 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. www.littelfuse.com 6-2 © 2006 Littelfuse, Inc. • Telecom Design Guide &XVWRPHU3UHPLVHV(TXLSPHQW&3( 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 Telecom Design Guide • © 2006 Littelfuse, Inc. 6-3 www.littelfuse.com &XVWRPHU3UHPLVHV(TXLSPHQW&3( 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 www.littelfuse.com 6-4 © 2006 Littelfuse, Inc. • Telecom Design Guide &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 4GHGTGPEG&GUKIPU Figure 6.6 Telecom Design Guide • © 2006 Littelfuse, Inc. 6-5 www.littelfuse.com 'LJLWDO6HWWRS%R[3URWHFWLRQ 'LJLWDO6HWWRS%R[3URWHFWLRQ 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 www.littelfuse.com 6-6 © 2006 Littelfuse, Inc. • Telecom Design Guide 'LJLWDO6HWWRS%R[3URWHFWLRQ 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. 6LJQDO3RUWV 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. Telecom Design Guide • © 2006 Littelfuse, Inc. 6-7 www.littelfuse.com 4GHGTGPEG&GUKIPU Video Signal Input 'LJLWDO6HWWRS%R[3URWHFWLRQ 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. www.littelfuse.com 6-8 © 2006 Littelfuse, Inc. • Telecom Design Guide 'LJLWDO6HWWRS%R[3URWHFWLRQ 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 4GHGTGPEG&GUKIPU Ethernet ports enable connection to LANs and so need medium to low energy protectors of low capacitance. Telecom Design Guide • © 2006 Littelfuse, Inc. 6-9 www.littelfuse.com +LJK6SHHG7UDQVPLVVLRQ(TXLSPHQW +LJK6SHHG7UDQVPLVVLRQ(TXLSPHQW 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. 3URWHFWLRQ5HTXLUHPHQWV 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. $'6/9'6/&LUFXLW3URWHFWLRQ 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 www.littelfuse.com 6 - 10 © 2006 Littelfuse, Inc. • Telecom Design Guide +LJK6SHHG7UDQVPLVVLRQ(TXLSPHQW 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 Telecom Design Guide • © 2006 Littelfuse, Inc. 6 - 11 www.littelfuse.com 4GHGTGPEG&GUKIPU Alternate ADSL Protection and VDSL Protection +LJK6SHHG7UDQVPLVVLRQ(TXLSPHQW 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. +'6/&LUFXLW3URWHFWLRQ 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) www.littelfuse.com 6 - 12 © 2006 Littelfuse, Inc. • Telecom Design Guide +LJK6SHHG7UDQVPLVVLRQ(TXLSPHQW 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 Telecom Design Guide • © 2006 Littelfuse, Inc. 6 - 13 www.littelfuse.com +LJK6SHHG7UDQVPLVVLRQ(TXLSPHQW 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. ,6'1&LUFXLW3URWHFWLRQ 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) www.littelfuse.com 6 - 14 © 2006 Littelfuse, Inc. • Telecom Design Guide +LJK6SHHG7UDQVPLVVLRQ(TXLSPHQW 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 Telecom Design Guide • © 2006 Littelfuse, Inc. 6 - 15 www.littelfuse.com 4GHGTGPEG&GUKIPU Protection Circuitry +LJK6SHHG7UDQVPLVVLRQ(TXLSPHQW 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. 3DLU*DLQ&LUFXLW3URWHFWLRQ 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. www.littelfuse.com 6 - 16 © 2006 Littelfuse, Inc. • Telecom Design Guide +LJK6SHHG7UDQVPLVVLRQ(TXLSPHQW 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. Telecom Design Guide • © 2006 Littelfuse, Inc. 6 - 17 www.littelfuse.com +LJK6SHHG7UDQVPLVVLRQ(TXLSPHQW 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 www.littelfuse.com 6 - 18 © 2006 Littelfuse, Inc. • Telecom Design Guide +LJK6SHHG7UDQVPLVVLRQ(TXLSPHQW 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 Telecom Design Guide • © 2006 Littelfuse, Inc. 6 - 19 www.littelfuse.com +LJK6SHHG7UDQVPLVVLRQ(TXLSPHQW 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. www.littelfuse.com 6 - 20 © 2006 Littelfuse, Inc. • Telecom Design Guide +LJK6SHHG7UDQVPLVVLRQ(TXLSPHQW 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. Telecom Design Guide • © 2006 Littelfuse, Inc. 6 - 21 www.littelfuse.com 4GHGTGPEG&GUKIPU 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) www.littelfuse.com 6 - 22 © 2006 Littelfuse, Inc. • Telecom Design Guide +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. Telecom Design Guide • © 2006 Littelfuse, Inc. 6 - 23 www.littelfuse.com $QDORJ/LQH&DUGV $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. www.littelfuse.com 6 - 24 © 2006 Littelfuse, Inc. • Telecom Design Guide $QDORJ/LQH&DUGV 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. Telecom Design Guide • © 2006 Littelfuse, Inc. 6 - 25 www.littelfuse.com 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 www.littelfuse.com 6 - 26 © 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 Telecom Design Guide • © 2006 Littelfuse, Inc. 6 - 27 www.littelfuse.com $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 www.littelfuse.com 6 - 28 © 2006 Littelfuse, Inc. • Telecom Design Guide $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 Telecom Design Guide • © 2006 Littelfuse, Inc. 6 - 29 www.littelfuse.com 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 www.littelfuse.com 6 - 30 © 2006 Littelfuse, Inc. • Telecom Design Guide $QDORJ/LQH&DUGV 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 Telecom Design Guide • © 2006 Littelfuse, Inc. 6 - 31 www.littelfuse.com $QDORJ/LQH&DUGV 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 www.littelfuse.com 6 - 32 © 2006 Littelfuse, Inc. • Telecom Design Guide $QDORJ/LQH&DUGV 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 Telecom Design Guide • © 2006 Littelfuse, Inc. 6 - 33 www.littelfuse.com 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 www.littelfuse.com 6 - 34 © 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 Telecom Design Guide • © 2006 Littelfuse, Inc. 6 - 35 www.littelfuse.com $QDORJ/LQH&DUGV 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 www.littelfuse.com 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 Telecom Design Guide • © 2006 Littelfuse, Inc. 6 - 37 www.littelfuse.com $QDORJ/LQH&DUGV 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 www.littelfuse.com 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 Telecom Design Guide • © 2006 Littelfuse, Inc. 6 - 39 www.littelfuse.com $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 www.littelfuse.com SLIC Protection with Series R and Quad Battrax 6 - 40 © 2006 Littelfuse, Inc. • Telecom Design Guide $QDORJ/LQH&DUGV %DWWUD[®3URWHFWLRQ*DWH%XIIHU&LUFXLW 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. 6 - 41 www.littelfuse.com 4GHGTGPEG&GUKIPU Figure 6.55 $QDORJ/LQH&DUGV 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. www.littelfuse.com 6 - 42 © 2006 Littelfuse, Inc. • Telecom Design Guide 3%;6\VWHPV 3%;6\VWHPV %UDQFK([FKDQJH6ZLWFKHV 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 3URWHFWLRQ5HTXLUHPHQWV 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 %UDQFK([FKDQJH5HIHUHQFH&LUFXLW 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. 6 - 43 www.littelfuse.com 4GHGTGPEG&GUKIPU PBX Figure 6.56 Line Cards Station Cards Matrix Switch Station Cards To Network &$79(TXLSPHQW &$79(TXLSPHQW As cable providers enter the local exchange market, protection of CATV (Community Antenna TV) equipment becomes even more critical in order to ensure reliable operation of equipment and uninterrupted service. 3URWHFWLRQ5HTXLUHPHQWV CATV line equipment should be able to withstand overvoltages that exceed 6000 V and surge currents up to 5000 A. CATV station protectors should be able to withstand overvoltages that exceed 5000 V and surge currents up to 1000 A. The SIDACtor® devices illustrated in Figure 6.57 through Figure 6.61 meet these requirements. The following regulatory requirements may apply: • UL 497C • SCTE IPS-SP-204 • SCTE Practices • NEC Article 830 3RZHU,QVHUWHUDQG/LQH$PSOLILHU5HIHUHQFH&LUFXLW 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 www.littelfuse.com CATV Amplifier Diagram 6 - 44 © 2006 Littelfuse, Inc. • Telecom Design Guide &$79(TXLSPHQW 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 Telecom Design Guide • © 2006 Littelfuse, Inc. 6 - 45 www.littelfuse.com 4GHGTGPEG&GUKIPU Power Port &$79(TXLSPHQW &$796WDWLRQ3URWHFWLRQ5HIHUHQFH&LUFXLW 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 www.littelfuse.com Gas Plasma Arrester CATV Station Protection 6 - 46 © 2006 Littelfuse, Inc. • Telecom Design Guide 3ULPDU\3URWHFWLRQ 3ULPDU\3URWHFWLRQ 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 3ULPDU\3URWHFWLRQ5HIHUHQFH&LUFXLW 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. 6 - 47 www.littelfuse.com 4GHGTGPEG&GUKIPU 3URWHFWLRQ5HTXLUHPHQWV 3ULPDU\3URWHFWLRQ 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 www.littelfuse.com SIDACtor Primary Protection 6 - 48 © 2006 Littelfuse, Inc. • Telecom Design Guide 3ULPDU\3URWHFWLRQ 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 4GHGTGPEG&GUKIPU Figure 6.65 Voltage and Sneak Current Protection P3203AC 4 W Heat Coil Figure 6.66 Balanced SIDACtor Primary Protection Telecom Design Guide • © 2006 Littelfuse, Inc. 6 - 49 www.littelfuse.com 6HFRQGDU\3URWHFWLRQ 6HFRQGDU\3URWHFWLRQ 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 3URWHFWLRQ5HTXLUHPHQWV 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 www.littelfuse.com CPE Protection 6 - 50 © 2006 Littelfuse, Inc. • Telecom Design Guide 6HFRQGDU\3URWHFWLRQ 6HFRQGDU\3URWHFWLRQ5HIHUHQFH&LUFXLW 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. 6 - 51 www.littelfuse.com 7ULDF3URWHFWLRQ 7ULDF3URWHFWLRQ 7K\ULVWRUV 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. 7K\ULVWRU5HIHUHQFH&LUFXLW 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 www.littelfuse.com 6 - 52 © 2006 Littelfuse, Inc. • Telecom Design Guide 'DWD/LQH3URWHFWRUV 'DWD/LQH3URWHFWRUV 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. 3URWHFWLRQ5HTXLUHPHQWV Data lines should be protected against overvoltages that can exceed 1500 V and surge currents up to 50 A. 'DWD/LQH5HIHUHQFH&LUFXLW 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 Telecom Design Guide • © 2006 Littelfuse, Inc. 6 - 53 www.littelfuse.com /$1DQG9R,33URWHFWRUV /$1DQG9R,33URWHFWRUV %DVH73URWHFWLRQ 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 www.littelfuse.com D3 D4 10Base-T Metallic and Longitudinal Protection 6 - 54 © 2006 Littelfuse, Inc. • Telecom Design Guide /$1DQG9R,33URWHFWRUV %DVH73URWHFWLRQ 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 4GHGTGPEG&GUKIPU Figure 6.74 D4 0461.500 P0642SA Figure 6.75 100 Base-T Protection Without External Compensation Telecom Design Guide • © 2006 Littelfuse, Inc. 6 - 55 www.littelfuse.com 127(6