S.一世DACtor Protection Thyristors

S.一世DACtor® Device Selection Criteria

When selecting aS.一世DACtor®设备,使用以下条件:

O.ff-state Voltage (VDRM

V.DRMS.一世DACtor® device must be greater than the maximum operating voltage of the circuit that theS.一世DACtor®设备是保护的。

Example 1:For a POTS (Plain Old Telephone Service) application, convert the maximum operating Ring voltage (150 VRMS) to a peak voltage, and add the maximum DC bias of the central office battery:

  • 150 Vrms.v2 + 56.6 VPK.= 268.8 VPK.
  • ∴VDRM>268.8 V

Example 2:For an ISDN application, add the maximum voltage of the DC power supply to the maximum voltage of the transmission signal (for U.S. applications, the U-interface will not have a DC voltage, but European and Japanese ISDN applications may):

  • 150 VPK.+ 3 V.PK.= 153 VPK.
  • ∴VDRM>153 V

S.witching Voltage (VS.

V.S.S.一世DACtor® device should be equal to or less than the instantaneous peak voltage rating of the component it is protecting.

Example 1:V.S.= VR.elay Breakdown

Example 2:V.S.= SLIC VPK.


对于不需要额外的串联电阻的电路,电流电流额定值(IPP.) 的S.一世DACtor® device should be greater than or equal to the surge currents associated with the lightning immunity tests of the applicable regulatory requirement (IPK.):

  • 一世PP.= IPK.

For circuits that use additional series resistance, the surge current rating (IPP.) 的S.一世DACtor® device should be greater than or equal to the available surge currents associated with the lightning immunity tests of the applicable regulatory requirement (IPK.(available)):

  • 一世PP.= IPK.(available)

这maximum available surge current is calculated by dividing the peak surge voltage (VPK.)通过总电路电阻(RT.O.T.一种L):

  • 一世PK.(available)= VPK./ R.T.O.T.一种L

For longitudinal surges (Tip-Ground, Ring-Ground), RT.O.T.一种Lis calculated for both Tip and Ring:

  • R.S.O.URCE= VPK./一世PK.
  • R.T.O.T.一种L= R小费+ R.S.O.URCE
  • R.T.O.T.一种L= R戒指+ R.S.O.URCE

For metallic surges (Tip-Ring):

  • R.S.O.URCE= VPK./一世PK.
  • R.T.O.T.一种L= R小费+ R.戒指+ R.S.O.URCE

Example 1:一种modem manufacturer must pass the Type A surge requirement of TIA-968-A without any series resistance.

  • 一世PK.= 100 A, 10x560 µs
  • IPP = 100a,10x560μs
  • 因此,“B”评分或“C”额定值S.一世DACtor® device would be selected.

Example 2:线卡制造商必须通过尖端和30°ON环上的GR 1089的浪涌要求。

  • 一世PK.= 100 A, 10x1000 µs
  • V.PK.= 1000 V
  • R.S.O.URCE= VPK./一世PK.= 10 O
  • R.T.O.T.一种L= RS.O.URCE+ R.小费= 40 o.
  • 一世PK.(available)= VPK./ R.T.O.T.一种L= 1000 V/40 O
  • ∴ IPP.= 25 A

Holding Current (IH

因为TIA-968-A指定在短路条件下,注册终端设备在每条导体下不超过140 mA DC,保持电流S.一世DACtor® device is set at 150 mA.

对于特定的设计标准,保持电流(iH) 的S.一世DACtor® device must be greater than the DC current that can be supplied during an operational and short circuit condition.

O.ff-State Capacitance (CO.

一种ssuming that the critical point of insertion loss is 70 percent of the original signal value, theS.一世DACtor®设备可用于大多数应用,传输速度高达30 MHz。用于传输速度大于
30 MHz,强烈推荐新的MC系列。

R.egulatory Requirements

由于业务中断的巨大成本和网络设备失败,电话服务提供商采用了各种规格来帮助规范他们购买的电信产品的可靠性和性能。在欧洲和远东大部分地区,最常见的标准是ITU-T K.20和K.21。

在北美,大多数经营公司都基于包含GR1089要求的NEB的要求,TIA-968-A(以前称为FCC部分68)和UL 60950-1。

T.his section is a paraphrase of existing documents and does not cover the listed recommendation, standard or regulatory requirements in their entirety. This information is intended to be used only as a reference. For exact specifications, obtain the referenced document from the appropriate source.

S.一世DACtor® Family Descriptions


这宽带优化™ family of products is focused on addressing the performance and regulatory requirements of broadband equipment. The宽带优化家庭,提供广泛的解决方案applications with the options needed to address the unique protection needs of DSL equipment (up to VDSL) as well as Ethernet (up to 1000baseT). Optimization is accomplished using proprietary and patented approaches that minimize the negative effects of device capacitance on broadband signals. The宽带优化家族提供过压保护解决方案,可帮助应用程序符合Telcordia GR-1089第4期,ITU-T建议书K.20,K.21,K.44和K.45。


S.LIC产品系列专注于解决SLIC(用户线路接口电路)芯片组的独特保护需求。家庭提供Fixed VoltageandBattrax®电池跟踪保护解决方案能够保护来自闪电和交流电源交叉引起的瞬态的切割器件。这S.LIC家族提供过压保护解决方案,可帮助应用程序符合Telcordia GR-1089第4期,ITU-T建议书K.20,K.21,K.44和K.45。


LCASfamily of products is focused on the specialized protection needs of Line Circuit Access Switches (LCAS). This family utilizes a specialized asymmetric design specially formulated for LCAS devices. TheLCAS家族提供过压保护解决方案,可帮助应用符合Telcordia GR-1089问题4,ITU-T建议书K.20,K.21,K.44和K.45。


基带family of products is focused on addressing the performance and regulatory requirements of baseband telecommunications equipment such as voice, modems, and DS1. They offer an overvoltage protection solution that helps applications comply with Telcordia GR-1089 Issue 4, ITU-T recommendations K.20, K.21, K.44, and K.45, and TIA-968-A.


High Surge Current产品是一个独特的家庭非常健壮的固体state protection devices intended for use in high exposure environments. This family includes products specifically designed for primary protection such as cell and TO-220 devices. TheHigh Surge Current家庭还有能够在极端条件下满足5KA 8 /20μs的设备。为了提高二级保护要求,DO-214封装中可提供一种能够为1000A 2 /10μs的D级设备。这High Surge CurrentProtection family provides an overvoltage protection solution that help applications comply with Telcordia GR-1089 Issue 4, and ITU-T recommendations K.20, K.21, K.44, and K.45.

S.一世DACtor® Family Application Selector Table

T.elecom Application 宽带优化™ Protection 切片保护 基带Protection (Voice-DS1) LCAS保护 高浪涌电流保护
HDSL2 / 4.
Ethernet 10/100/1000BaseT
Negative Ringing SLIC
Positive & Negative Ringing SLIC
LCAS Relay
POTS-Telephone-corded & cordless
MDC Modem
PCI Modem
Multifunction Printer-Fax
T.1/E1/J1 (DS1)
S.ecurity System
Primary Protection Modules
S.econdary Protection Modules-Strip Protectors
CATV Power Amplifiers
Base Stations




Key parameters forS.一世DACtor设备是V.DRM一世DRMV.S.一世H, 和V.T.(please refer to Figure 1.3 on page 11).

V.DRMis the repetitive peak off-state voltage rating of the device (also known as stand-off voltage) and is the continuous peak combination of AC and DC voltage that may be applied to theS.一世DACtordevice in its off-state condition.

一世DRMis the maximum value of leakage current that results from the application of VDRM

开关电压(VS.是在快速上升(100V /μs)过电压条件期间可以经受后续组件的最大电压。

保持电流(iHis the minimum current required to maintain the device in the on state.

O.n-state voltage (VT.is the maximum voltage across the device during full conduction.


该设备类似于开关操作。在关闭状态下,设备表现出泄漏电流(iDRM)小于5μA,使其无法保护电路。由于瞬态电压超过设备vDRM那the device begins to enter its protective mode with characteristics similar to an avalanche diode. When supplied with enough current (IS.)那the device switches to an on state, shunting the surge from the circuit it is protecting. While in the on state, the device is able to sink large amounts of current because of the low voltage drop (VT.)在整个设备上。一旦流过设备的电流被中断或低于最小保持电流(iH)那the device resets, returning to its off state. If the IPP.rating is exceeded, the device typically becomes a permanent short circuit.



Figure 1.2 Geometric Structure of BidirectionalS.一世DACtor设备


一种s the voltage across the device increases and exceeds the device's VDRM那the electric field across the center junction reaches a value sufficient to cause avalanche multiplication. As avalanche multiplication occurs, the impedance of the device begins to decrease, and current flow begins to increase until the device's current gain exceeds unity. Once unity is exceeded, the device switches from a high impedance (measured at VS.)to a low impedance (measured at VT.)until the current flowing through the device is reduced below its holding current (IH)。

O.vervoltage Protection Comparison

这four most commonly used technologies for overvoltage protection are as follows:

  • S.一世DACtor® devices
  • 气体排放管(GDT)
  • Metal Oxide Varistors (MOVs)
  • T.V.S.diodes


S.一世DACtor® devices

一种S.一世DACtor®设备是一种PNPN设备,可以被认为是没有门的晶闸管设备。超过其峰值关闭状态电压(VDRM)那aS.一世DACtor®设备将钳位到设备的开关电压内的瞬态电压(V.S.)rating. Then, once the current flowing through theS.一世DACtor® device exceeds its switching current, the device will crowbar and simulate a short-circuit condition. When the current flowing through theS.一世DACtor® device is less than the device's holding current (IH)那theS.一世DACtor®设备将重置并返回其高隧it阻抗。


一种dvantages of theS.一世DACtor® device include its fast response time (Figure 1.1), stable electrical characteristics, long term reliability, and low capacitance. Also, because theS.一世DACtor® device is a crowbar device, it cannot be damaged by voltage.


Because theS.一世DACtor® device is a crowbar device, it cannot be used directly across the AC line; it must be placed behind a load. Failing to do so will result in exceeding theS.一世DACtor® device's maximum on-state current rating, which may cause the device to enter a permanent short-circuit condition.


一种lthough found in other applications,S.一世DACtor® devices are primarily used as the principle overvoltage protector in telecommunications and data communications circuits. For applications outside this realm, follow the design criteria in "S.一世DACtor®设备选择标准“。




20 kA, and capacitance ratings can be as low as 1 pF with a zero-volt bias.



Metal Oxide Varistors

Metal Oxide Varistors (MOVs) are two-leaded, through-hole components typically shaped in the form of discs. Manufactured from sintered oxides and schematically equivalent to two back-to-back PN junctions, MOVs shunt transients by decreasing their resistance as voltage is applied.




一种lthough MOVs are restricted from use in many telecom applications (other than disposable equipment), they are useful in AC applications where a clamping device is required and tight voltage tolerances are not.


T.ransient Voltage Suppressor (TVS) diodes are clamping voltage suppressors that are constructed with back-to-back PN junctions. During conduction, TVS diodes create a low impedance path by varying their resistance as voltage is applied across their terminals. Once the voltage is removed, the diode will turn off and return to its high off-state impedance.




Due to their low power ratings, TVS diodes are not used as primary interface protectors across Tip and Ring, but they can be used as secondary protectors that are embedded within a circuit.

O.vershoot Levels versus dv/dt

Firgure 1.4 below shows a peak voltage comparison betweenS.一世DACtor®装置,气体排放管(GDT),金属氧化物压敏电阻(MOV)和TVS二极管,所有具有230 V的标称脱扣电压等级。X轴代表DV / DT(相对于电压上升)应用于每个保护器的时间),y轴表示每个保护器上的最大电压降。

Figure 1.4 Overshoot Levels versus dv/dt

T.elecommunications Protection




一种s this occurs, the current traveling through the conductive shield of the cable produces an equal voltage on both the Tip and Ring conductors at the terminating ends. Known as a longitudinal voltage surge, the peak value and waveform associated with this condition is dependent upon the distance the transient travels down the cable and the materials with which the cable is constructed.


Power Fault

一种nother system transient that is a common occurrence for telecommunications cables is exposure to the AC power system. The common use of poles, trenches, and ground wires results in varying levels of exposure which can be categorized as direct power fault, power induction, and ground potential rise.

Direct power fault occurs when a power line makes direct contact to telecommunications cables. Direct contact is commonly caused by falling trees, winter icing, severe thunderstorms, and vehicle accidents. Direct power fault can result in large currents being present on the line.

Power induction is common where power cables and telecommunications cables are run in close proximity to one another. Electromagnetic coupling between the cables results in system transients being induced onto the telecommunications cables, which in turn can cause excessive heating and fires in terminal equipment located at the cable ends.

Ground potential rise is a result of large fault currents flowing to Ground. Due to the varying soil resistivity and multiple grounding points, system potential differences may result.


闪电是大自然最常见和最危险的现象之一。在任何时候,全球有大约2,000次雷暴正在进入,闪电每秒超过100次撞击地球。根据IEEE C.62,在美国的一年内,雷电平均每平方英里平均52次,导致100人死亡,250次伤害,设备财产受损超过1亿美元。

这Lightning Phenomenon

Lightning is caused by the complex interaction of rain, ice, up drafts, and down drafts that occur during a typical thunderstorm. The movement of rain droplets and ice within the cloud results in a large build up of electrical charges at the top and bottom of the thunder cloud. Normally, positive charges are concentrated at the top of the thunderhead while negative charges accumulate near the bottom. Lightning itself does not occur until the potential difference between two charges is great enough to overcome the insulating resistance of air between them.

Formation of Lightning



这initial flash of a lightning bolt results when the stepped leader and the streamer make connection resulting in the conduction of current to Ground. Subsequent strokes (3-4) occur as large amounts of negative charge move farther up the stepped leader. Known as return strokes, these subsequent bolts heat the air to temperatures in excess of 50,000°F and cause the flickering flash that is associated with lightning. The total duration of most lightning bolts lasts between 500 millisecond and one second.

During a lightning strike, the associated voltages range from 20,000 V to 1,000,000 V while currents average around 35,000 A. However, maximum currents associated with lightning have been measured as high as 300,000 A.

10 Key Facts about Lightning

  1. Lightning strikes the earth on an average of 100 times per second.
  2. Lightning strikes can affect computers and other electronic equipment as far as a kilometer away.
  3. 闪电在电源,数据通信和信号和电话线上导致瞬态过电压(非常快速的电涌)。这些浪涌然后携带并影响脆弱的设备。
  4. 风险包括计算机和电子设备peripheral equipment, building management systems, IP-PBX systems, CATV equipment, fire and security systems, PoE systems, and lighting arrays.
  5. T.ransient overvoltages can cause instant damage to equipment and its circuitry, leading to costly and lengthy stoppages to operation and latent damage, and can result in breakdowns weeks or months later.
  6. 甚至具有结构防雷的建筑物的设备仍然有很大的风险,因为结构保护旨在防止对建筑物的损坏并防止生命损失。
  7. While most businesses are at risk, campus or multi-building sites tend to be especially vulnerable.
  8. Lightning can and does strike in the same place and can strike the same place multiple times. Sites that have suffered once are proven vulnerable and often suffer again within a matter of months.
  9. Protecting electronic systems from transient overvoltage damage costs only a fraction of the cost of damage.
  10. Littelfuse designs and manufactures quality lightning protection equipment.

S.urge Waveforms for Various Standards
GR 1089‐Core
一世T.U-T K.20 and K.21
T.一世一种-968-A (formerly known as FCC Part 68)
T.一世一种-968-A (formerly known as FCC Part 68)
一世EC 61000-4-2, 4-4 and 4-5 Summary
Mainland China Standard-YD/T 950-1998
Mainland China Standard-YD/T 993-1998
中国大陆标准-YD / T 1082-2000
认证and Accreditation Administration
的People's Republic of China
UL 497.
UL 497.一种
UL 497.B
UL 497.C
UL 497.D
UL 60950-1 2nEdition

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