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| SMT50 ELECTRICAL CHARACTERISTICS The electrical characteristics of a SMT50 device are similar to that of a self-gated Triac, but the SMT50 is a two terminal device with no gate. The gate function is achieved by an internal current controlled mechanism. Like the T.V.S. diodes, the SMT50 has a standoff voltage (Vrm) which should be equal to or greater than the operating voltage of the system to be protected. At this voltage (Vrm) the current consumption of the SMT50 is negligible and will not affect the protected system. Resetting of the device to the non-conducting state is When a transient occurs, the voltage across the SMT50 will increase until the breakdown voltage (Vbr) is reached. At this point the device will operate in a similar way to a T.V.S. device and is in avalanche mode. As with the avalanche T.V.S. device, if the SMT50 is subjected The voltage of the transient will now be limited and will only increase by a few volts as the device diverts more current. As this transient current rises, a level of current through the to a surge current which is beyond its maximum rating, then the device will fail in short circuit mode, ensuring that the equipment is ultimately protected. controlled by the current flowing through the device. When the current falls below a certain value, known as the Holding Current (Ih), the device resets automatically. device is reached (Ibo) which causes the device to switch to a fully conductive state such that the voltage across the device is now only a few volts (Vt). The voltage at which the device switched from the avalanche mode to the fully conductive state (Vt) is known as the Breakover voltage (Vbo). When the device is in the Vt state, high currents can be diverted without damage to the SMT50 due to the low voltage across the device, since the limiting factor in such devices is dissipated power (V x I). SELECTING A SMT50 1. When selecting a SMT50 device, it is important that the Vrm of the device is equal to or greater than the the operating voltage of the system. 2. The minimum Holding Current (Ih) must be greater than the current the system is capable of delivering otherwise the device will remain conducting following a transient condition. V-I Graph illustrating symbols and terms for the SMT50 surge protection device. IBO IH IRM VRM VBR VBO VR V Ipp I COMPLIES WITH THE FOLLOWING STANDARDS PEAK SURGE VOLTAGE (V) VOLTAGE WAVEFORM (S) 10/700 10/700 10/700 1.2/50 10/700 1.2/500 10/160 10/560 9/720 2/10 10/1000 2/10 0.5/700 CURRENT WAVEFORM (S) 5/310 5/310 5/310 1/20 5/310 8/20 10/160 10/560 5/320 2/10 10/1000 2/10 0.8/310 ADMISSIBLE IPP NECESSARY RESISTOR () 12.5 6.5 11.5 10 11.5 - (A) 25 38 50 50 50 100 75 55 25 150 50 150 25 (CCITT) ITU-K20 (CCITT) ITU-K17 VDE0433 VDE0878 IEC-1000-4-5 FCC Part 68, lightning surge type A FCC Part 68, lightning surge type B Bellcore TR-NWT-001089 first level Bellcore TR-NWT-001089 second level CNET I31-24 1000 1500 2000 2000 level 3 level 4 1500 800 1000 2500 1000 5000 1000 48 w w w. l i t t e l f u s e . c o m SMT50 ELECTRICAL CHARACTERISTICS (Tamb 25C) SYMBOL V RM I RM VR V BR C PARAMETER Stand-off Voltage Leakage Current at Stand-off Voltage Continuous Reverse Voltage Breakdown Voltage Capacitance SYMBOL V BO IH I BO I PP PARAMETER Breakover Voltage Holding Current Breakover Current Peak pulse Current THERMAL RESISTANCE SYMBOL RTH (J-I) RTH (J-I) PARAMETER Junction to leads Junction to ambient on printed circuit (with standard footprint dimensions) VALUE 20 100 UNIT C/W C/W ABSOLUTE MAXIMUM RATINGS (Tamb 25C) SYMBOL P IPP PARAMETER Power dissipation Peak pulse current Tlead 10/1000S 8/20S I TSM dV/dt Tstg Tj TL Non repetitive surge peak on-state current Critical rate of rise of off-state voltage Storage temperature range Maximum junction temperature Maximum lead temperature for soldering during 10s tp + 20ms VRM VALUE 5 50 100 30 5 -55 to +150 150 260 UNIT W A A A KV/S C C Tstg Type Marking IRM @ VRM MAX (A) 2 2 2 2 2 2 2 2 2 2 (V) 56 60 90 180 117 162 180 198 216 243 IRM @ VR MAX (A) 50 50 50 50 50 50 50 50 50 50 (V) 62 68 100 120 130 180 200 220 240 270 VBO @ IBO MAX (V) 82 90 133 160 173 240 267 293 320 360 (mA) 800 800 800 800 800 800 800 800 800 800 IH MIN (Note 1) C MAX (pF) 150 150 100 100 100 100 100 100 100 100 Laser SMT50-62 SMT50-68 SMT50-100 SMT50-120 SMT50-130 SMT50-180 SMT50-200 SMT50-220 SMT50-240 SMT50-270 A062 A068 A100 A120 A130 A180 A200 A220 A240 A270 (mA) 150 150 150 150 150 150 150 150 150 150 All parameters are tested @ 25C except where indicated. Note 1: Measured @ 1V bias, 1MHZ All parameters are tested using a FET TEST model 3600 TM w w w. l i t t e l f u s e . c o m 49 SMT50 50 w w w. l i t t e l f u s e . c o m |
Price & Availability of SMT50-68
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