1. XC6221A25A7R-G Substitution Conclusion The XC6221A25A7R-G can serve as a conditional substitute. Compared to the original part XC6501D25A7R-G, the key differences are as follows: First, the quiescent current (Iq) increases from 19µA to 50µA, resulting in higher power consumption for the substitute during standby or light-load conditions, which may slightly reduce battery life in portable applications. Second, the power supply rejection ratio (PSRR) is significantly improved from 50dB to 70dB @ 1kHz. This indicates the substitute offers substantially enhanced rejection of input supply ripple and noise, providing a cleaner output voltage to the load—a particular advantage for noise-sensitive RF or analog circuits. While both devices are package-compatible and share critical specifications (input/output voltage, maximum current), the application's priority between low quiescent current and high PSRR must be evaluated.