Led Design Guide Page 25 LED Design Guide

2015 Littelfuse LED Lighting Design Guide www.littelfuse.com LED Lighting Design Guide The most important of these is V R , which is should be equal to, or greater than, the peak operating level of the circuit (or the part of the circuit) to be protected. This will ensure that the TVS does not clip the circuit drive voltage. I PP is the maximum current the TVS can withstand without damage and is usually stated in reference to an exponential waveform such as 101000s. The required I PP can only be determined by dividing the peak transient voltage by the source impedance. The maximum clamping voltage (V C ) is the peak voltage that will appear across the TVS device when subjected to the Peak Pulse Current (I PP ), based on the referenced exponential waveform. Keep in mind that the failure mechanism in a TVS diode is a short circuit. Therefore, if the TVS fails due to a transient, the circuit it's in will still be protected. Figure 14 illustrates some Littelfuse TVS diode package configurations, which will fit in a wide range of applications. Figure 14. Littelfuse TVS diodes are available in a wide range of sizes, configurations, and ratings. When selecting a TVS diode, the first step is to define the operating parameters of the circuit to be protected, whether it's an LED driver or something else. Table 7 lists the most important circuit parameters to be considered. Design Considerations for TVS Diodes (continued) 25

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