Led Design Guide Page 19 LED Design Guide

2015 Littelfuse LED Lighting Design Guide www.littelfuse.com LED Lighting Design Guide How does one know if and when the thermal element has cleared? The Littelfuse iTMOV varistor series adds an additional third indicator lead that provides access to the connection between the thermal element and the MOV electrode. Having access to this point of the circuit makes indication of the thermal element a simple procedure. Figure 10 shows a simple application circuit with indication. Fuse Line TMOV Varistor TMOV20R130M Neutral 120VAC D1 LED Normally On R1 47k,0.5W Figure 10. Indicator circuit using the Littelfuse iTMOV varistor (LED normally on). In Figure 10 , an iTMOV varistor is used to protect the L-N connection of a typical U.S. 120Vac line. An AC rated LED is placed across the iTMOV varistor's indicator lead and the Neutral line. See the TMOV and iTMOV Varistor Series datasheet for more detail on these Littelfuse products. Design Considerations in MOV Selection (continued) 19

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