1. PS2581AL2-A Substitution Conclusion The PS2581AL2-A cannot serve as a direct replacement for the PS2581L2-A, as its key performance parameters are comprehensively downgraded. It is only suitable for circuits with more relaxed requirements for output capability and efficiency. The differences are reflected in the following aspects: the output current is reduced from 50 mA to 30 mA, significantly weakening its load-driving capability; the maximum output withstand voltage drops from 80 V to 70 V, limiting its applicability in high-side circuits; the maximum forward current decreases from 80 mA to 30 mA, reducing the input-side drive margin; and the minimum current transfer ratio (CTR) falls from 80% to 50%, indicating lower optocoupler conversion efficiency, which may result in insufficient output transistor conduction under the same input conditions. If the original design already operates close to the limits of the original part, forced substitution may lead to inadequate circuit performance or failure. A thorough re-evaluation of actual operating conditions—such as load current, voltage margin, and CTR degradation—must be conducted before any cautious assessment.