1. XC6501C2717R-G Substitution Conclusion Feasible, but only as a conditional downgrade substitution. It is recommended only in applications with stringent requirements for power efficiency and quiescent current, where input-to-output voltage headroom and power supply noise rejection are not critical. The key differences are as follows: First, the quiescent current (Iq) is reduced from 50µA to 20µA, significantly lowering its own power consumption under light-load or standby conditions, which helps extend battery life. Second, the dropout voltage at a 200mA full load increases to 0.38V (compared to the original part's 0.17V at 100mA; extrapolating to 200mA shows the original part's performance is far superior). This significantly raises the minimum input voltage required to maintain a stable output, narrowing the effective operating voltage range in applications where the input voltage is close to the output voltage, such as in battery-powered systems. Third, the power supply rejection ratio (PSRR) drops from 70dB to 50dB, degrading its ability to suppress input ripple and noise by approximately a factor of 10. This may lead to performance degradation in RF or high-precision analog circuits.