SMT100 ELECTRICAL CHARACTERISTICS The electrical characteristics of a SMT100 device are similar to device is reached (Ibo) which causes the device to switch to a that of a self-gated Triac, but the SMT100 is a two terminal fully conductive state such that the voltage across the device device with no gate. The gate function is achieved by an is now only a few volts (Vt). The voltage at which the device internal current controlled mechanism. switched from the avalanche mode to the fully conductive state (Vt) is known as the Breakover voltage (Vbo). When the Like the T.V.S. diodes, the SMT100 has a standoff voltage device is in the Vt state, high currents can be diverted (Vrm) which should be equal to or greater than the operating without damage to the SMT100 due to the low voltage across voltage of the system to be protected. At this voltage (Vrm) the device, since the limiting factor in such devices is the current consumption of the SMT100 is negligible and will dissipated power (V x I). not affect the protected system. Resetting of the device to the non-conducting state is When a transient occurs, the voltage across the SMT100 will controlled by the current flowing through the device. When increase until the breakdown voltage (Vbr) is reached. At this the current falls below a certain value, known as the Holding point the device will operate in a similar way to a T.V.S. Current (Ih), the device resets automatically. device and is in avalanche mode. As with the avalanche T.V.S. device, if the SMT100 is subjected The voltage of the transient will now be limited and will only to a surge current which is beyond its maximum rating, then increase by a few volts as the device diverts more current. As the device will fail in short circuit mode, ensuring that the this transient current rises, a level of current through the equipment is ultimately protected. SELECTING A SMT100 1. When selecting a SMT100 device, it is important V-I Graph illustrating symbols that the Vrm of the device is equal to or greater than and terms for the SMT100 the the operating voltage of the system. surge protection device I Ipp IBO IH 2. The minimum Holding Current (Ih) must be greater IRM V VRM than the current the system is capable of delivering VBR VBO VR otherwise the device will remain conducting following a transient condition. COMPLIES WITH THE FOLLOWING STANDARDS PEAK SURGE VOLTAGE (V) VOLTAGE WAVEFORM (µS) CURRENT WAVEFORM ADMISSIBLE IPP (µS) (A) NECESSARY RESISTOR (CCITT) ITU-K20 1000 10/700 5/310 25 - (CCITT) ITU-K17 1500 10/700 5/310 38 - VDE0433 2000 10/700 5/310 50 - VDE0878 2000 1.2/50 1/20 50 - level 3 10/700 5/310 50 - level 4 1.2/500 8/20 100 - FCC Part 68, lightning surge 1500 10/160 10/160 75 12.5 type A 800 10/560 10/560 55 6.5 FCC Part 68, lightning surge 1000 9/720 5/320 25 11.5 IEC-1000-4-5 type B Bellcore TR-NWT-001089 2500 2/10 2/10 150 first level 1000 10/1000 10/1000 50 10 Bellcore TR-NWT-001089 5000 2/10 2/10 150 11.5 1000 0.5/700 0.8/310 25 - second level CNET I31-24 w w w. l i t t e l f u s e . c o m 51 SMT100 ELECTRICAL CHARACTERISTICS (Tamb 25°C) SYMBOL PARAMETER SYMBOL PARAMETER V RM Stand-off Voltage I RM Leakage Current at Stand-off Voltage IH Holding current VR Continuous Reverse Voltage I BO Breakover Current V BR Breakdown Voltage I PP Peak pulse Current C Capacitance IR Continuous Reverse Current V RO Breakover Voltage THERMAL RESISTANCE SYMBOL PARAMETER RTH (J-I) RTH (J-I) VALUE UNIT Junction to leads 20 Junction to ambient on printed circuit 100 °C/W °C/W (with standard footprint dimensions) ABSOLUTE MAXIMUM RATINGS (Tamb 25°C) SYMBOL PARAMETER I PP Peak pulse Current: I TSM VALUE UNIT 10/1000µS (open circuit voltage waveform 1kV 10/1000µS) 100 A 5/310µS (open circuit voltage waveform 4kV 10/700µS) 150 A 8/20µS (open circuit voltage waveform 4kV 1.2/50µS) 250 A 2/10µS (open circuit voltage waveform 2.5kV 2/10µS) 500 A Non-repetitive surge peak on-state current 50Hz 55 A F = 50Hz 60Hz 60 A Non-repetitive surge peak on-state current 0.2s 25 A 2s 12 A 260 °C -55 to +150 °C °C F = 50Hz TL Maximum lead temperature range Tstg Storage temperature range Tj Maximum junction temperature Type Marking 150 IRM @ VRM MAX IRM @ VR MAX VBO @ IBO MAX IH MIN C MAX (Note 1) Laser (µA) (V) (µA) (V) (V) (mA) (mA) (pF) SMT100-35 B035 2 32 50 35 55 800 150 180 SMT100-65 B065 2 55 50 65 80 800 150 160 SMT100-120 B120 2 110 50 120 160 800 150 140 SMT100-140 B140 2 120 50 140 200 800 150 140 SMT100-200 B200 2 170 50 200 265 800 150 130 SMT100-230 B230 2 200 50 230 300 800 150 120 SMT100-270 B270 2 230 50 270 350 800 150 120 Note 1: Measured @ 1V bias, 1MHZ. TM All parameters are tested using a FET TEST model 3600. 52 w w w. l i t t e l f u s e . c o m SMT100 w w w. l i t t e l f u s e . c o m 53