1. ISO722DRG4 Substitution Conclusion Direct replacement of the original SI8718BC-A-IS with the ISO722DRG4 is conditionally feasible, but presents critical limitations in high-voltage isolation and low-voltage high-side supply scenarios. The key differences are as follows: First, the isolation voltage rating drops from 3750 Vrms to 2500 Vrms. In designs requiring higher insulation levels—such as reinforced insulation or those subjected to larger surge voltages—the substitute risks insufficient safety margin. The system’s insulation requirements must be re-evaluated accordingly. Second, the lower supply voltage limit increases from 2.5 V to 3 V. If the original design operates the high-side (input side) between 2.5 V and 3 V—for example, in 2.5 V or 3.0 V logic systems—the ISO722DRG4 will not function correctly. Power supply compatibility must therefore be verified. From a performance standpoint, the ISO722DRG4 offers clear advantages over the original part: higher data rate (100 Mbps vs. 15 Mbps), improved transmission delay and distortion (24 ns propagation delay, 2 ns pulse-width distortion), and superior switching speed. This makes it a better choice for signal integrity, timing accuracy, and high-speed applications. Its 25 kV/µs common-mode transient immunity (CMTI) remains acceptable in most industrial noise environments. Package compatibility (8-SOIC) and unidirectional single-channel architecture are identical. In summary, if the application’s actual isolation withstand voltage requirement is below 2500 Vrms and the high-side supply voltage is ≥3 V, the ISO722DRG4 represents a performance-upgraded, qualified substitute. Otherwise, a device with matching isolation voltage and supply range should be selected.