1.5SMC91AT3 from ON Semiconductor is a TVS diode intended for circuit protection in designs exposed to transient voltage events such as ESD, surge, and other overvoltage conditions. Components in this category are commonly used to help protect power lines, industrial interfaces, automotive-related electronics, telecom equipment, and embedded control boards where transient suppression supports long-term reliability. For engineers, this part is positioned as a practical protection device for designs that need robust surge handling in a compact diode format, especially where board-level protection is part of the overall compliance and durability strategy. The current lifecycle status for 1.5SMC91AT3 is information not available from the provided data, so design teams should confirm manufacturer lifecycle guidance before locking it into new programs. RoHS compliance information is also not available from the provided input. Engineers and procurement teams should verify the latest datasheet, material declaration, and manufacturer compliance statements before qualification or volume purchasing.