Mlv Design Guide Page 5 Sensitivity Of The Electronics System

Protection Device Selection Considerations Four different device technologies are designed for transient suppression: TVS diodes, multilayer varistors (MLVs), TVS diode arrays, and polymer ESD suppressors. Table 3 summarizes the various transient protection solutions available. Type of Threat Typical Application Typical Protection Device Used Main Selection Criteria Lightning Equipment connected to external power and communication lines Protection thyristors, TVS diodes, gas discharge tubes (GDTs), MOVs Operating voltage, breakover/ clamping voltage, surge energy/power/ current ratings ESD (Electrostatic Discharge) Electronic equipment with human interfaces and data ports MLVs, MOVs, polymer ESD suppressors, TVS diodes Uni-/bidirectional, ESD voltage rating, low dynamic resistance, low clamping voltage, low capacitance EFT (Electrical Fast Transient) Equipment that has, or is connected to, a system or circuit with switched inductive loads or mechanical relays MLVs, MOVs, polymer ESD suppressors, TVS diodes Energy/peak current rating, operating voltage, surge current rating Inductive load switching and commutative spikes Equipment associated with large motors, generators, pumps, compressors, relays, and AC power distribution MLVs, MOVs, polymer ESD suppressors, TVS diodes, GDTs Proper blocking voltage and current carrying capacity Note: MLV devices are rated at 125C and suitable for harsh environment applications. Multilayer Varistor as Surge Protection Solution MLVs are clamping devices used for board level protection from ESDs, EFTs, and other transients that can occur on power supply, data, and control lines if the lines can tolerate higher capacitance. MLVs offer a cost-effective solution in a range of popular industry-standard discrete component sizes. Some MLVs also offer low band-pass characteristics that filter high frequency noise from the circuit being protected. MLVs are typically used when: Power supply line or low/medium speed data and signal lines are to be protected. Transient currents or energy beyond ESD is expected (that is, EFT and lightning-induced surges) Designers looking to replace high wattage TVS Zener Diodes (300W-1500W). Added capacitance is desirable for EMI filtering (3p-4500pF). The operating voltage (up to 120VDC) is above silicon or polymer ESD suppressor ratings. I V Typical IV Curve for a single channel bidirectional TVS Diode Array Typical IV Curve for a MLV device 2) MLV device had lower leakage current than the TVS diode at a given bias DC voltage 1) MLV intrinsically offers higher bias voltage than the TVS diode array. Table 3. Protection Technology Comparison Figure 7. The IV Curve of Typical MOV Sharp 2016 Littelfuse Multilayer Varistors (MLVs) Design Guide www.littelfuse.com Surface Mount Multilayer Varistors (MLVs) Design Guide Transient Threats Vs. Sensitivity of the Electronics System (continued) 5

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