1. Certification Grade Difference: The BZT52-B7V5S-AU_R1_000A1 is explicitly marked “Grade: Automotive” and is certified to “AEC-Q101.” This model has passed the stress test standards for discrete semiconductor devices established by the Automotive Electronics Council, with its reliability, consistency, and long-term performance under extreme temperature, humidity, and vibration conditions rigorously validated. The AU model is suitable for applications with stringent long-term reliability and low failure probability demands, such as the automotive front‑end market. Its production process, quality control, and supply chain traceability systems comply with automotive industry standards. In contrast, standard models typically meet only industrial or commercial‑grade specifications and may exhibit higher long‑term failure rates under identical electrical stress compared to automotive‑grade products. 2. Root Cause of Price Difference: The seven‑fold price gap is primarily attributed to the aforementioned certification and the higher manufacturing/testing standards. For applications such as consumer electronics or general industrial control, using an automotive‑grade device constitutes “over‑design” and introduces unnecessary cost increases. Reverse substitution (replacing an automotive‑grade part with a standard‑grade one) is generally not feasible, as it would fail to meet system reliability certification requirements (e.g., ISO/TS 16949). Summary: The core electrical performance of both models is identical. The primary distinction lies in the reliability grade and corresponding application certification. Selection should be based on the reliability requirements of the end application, not on electrical functionality alone.