1. SI8715BC-A-ISR Substitution Conclusion This part can conditionally replace the ISO721MDG4, provided that speed and timing performance compatibility are carefully evaluated. Key differences are as follows: the SI8715 supports a data rate of only 15 Mbps (original part: 150 Mbps), exhibits a propagation delay of 50 ns (original: 16 ns), and has a pulse‑width distortion of 25 ns (original: 1 ns). In high‑speed signaling or precision timing‑critical applications, substitution may degrade signal integrity, increase bit‑error rates, or disrupt system timing, rendering it unsuitable for the original high‑speed communication link. However, the SI8715 offers higher isolation voltage (3750 Vrms) and CMTI (35 kV/µs), which can provide stronger isolation reliability in low‑speed, high‑noise environments. Its wider supply range (starting from 2.5 V) also benefits low‑voltage designs. Substitution may be acceptable if the original application operates at very low speed (≤15 Mbps) and has sufficient timing margin.