Aumov LV Ultramov Varistor Design Guide Page 9 Varistor Design Guide For DC & Automotive Applications

DC Application Varistor Design Guide 2015 Littelfuse DC Application Varistor Design Guide www.littelfuse.com Load Dump Load dump is what happens to the supply voltage in a vehicle when a load is removed. If a load is removed rapidly (such as when the battery is disconnected while the engine is running), the voltage may spike before stabilizing, which can damage electronic components. In a typical 12V circuit, load dump can rise as high as 120V and take as long as 400 milliseconds to decay-more than enough time to cause serious damage. T 1 V B V S = 25V to 125V V B = 14V V S 90% 10% t V T 1 = 5ms to 10ms T= 40ms to 400ms Load dump waveform (from ISO 7637) Automotive MOV Background and Application Examples (continued) 8

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