Mlv Design Guide Page 4 Sensitivity Of The Electronics System

Figure 6. Circuit Board Damage Due to ESD Recurring transients are frequently caused by the operation of motors, generators, or the switching of reactive circuit components. Random transients, on the other hand, are often caused by lightning and ESD, which generally occur unpredictably, and may require elaborate monitoring to be accurately measured, especially if induced at the circuit- board level. Numerous electronics standards groups have analyzed transient voltage occurrences using accepted monitoring or testing methods. As component sizes shrink, electronic components exhibit increased sensitivity to electrical stresses. Microprocessors, for example, have structures and conductive paths that are unable to handle high currents from ESD transients. Such components operate at very low voltages, so voltage disturbances must be controlled to prevent device interruption and latent or catastrophic failures. Sensitive microprocessors are prevalent today in a wide range of devices. Everything from home appliances, such as dishwashers, to industrial controls and even toys use microprocessors to improve functionality and efficiency. Most vehicles now also employ multiple electronic systems to control the engine, climate, braking and, in some cases, steering, traction, and safety systems. Many of the supporting components, such as electric motors or accessories within appliances and automobiles, present transient threats to the entire system. Careful circuit design should not only factor in environmental effects but the potential effects of these related components. Table 2 shows the vulnerability of various component technologies. Voltage Current Rise Time Duration Protection Device Application Area Lighting 25kV 200kA 10 s 1ms MOV/TVS/SIDACtor Telecom Switching 600V 500A 20 s 500ms MOV/TVS/SIDACtor Industrial/Power System EMP 1kV 10A 20ns 1ms MOV/MLV Industrial/Power System ESD 15kV 30A <1ns 100ns MLV/PGB/ Diode Array Consumer Industrial Device Type Vulnerability (Volts) VMOS 30-1800 MOSFET 100-200 GaAsFET 100-300 EPROM 100 JFET 140-7000 CMOS 250-3000 Schottky Diode 300-2500 Bipolar Transistor 380-7000 SCR 680-1000 Power MOSFET 100-2000 IGBT 4000-8000 Table 1. Key Characteristics of Several Common Transients Table 2. Range of Device Vulnerability Surface Mount Multilayer Varistors (MLVs) Design Guide 2016 Littelfuse Multilayer Varistors (MLVs) Design Guide Transient Threats Vs. Sensitivity of the Electronics System 4

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