Fixed 3.3V rail from a 10V input — dropout and PSRR matter
The REG102UA-3.3 is a single-output linear regulator delivering a fixed 3.3V at up to 250 mA from a maximum input of 10V. Maximum dropout is 270 mV at full load — the input rail must stay at least 270 mV above 3.3V across the load range, or the output falls out of regulation. This is a standard 8-SOIC surface-mount part, suited for board-level point-of-load regulation where a clean, low-noise 3.3V rail is needed. PSRR is 65 dB at 120 Hz, typical for a linear regulator in this class — it attenuates 120 Hz ripple from a full-wave rectified input by roughly 1800×. If the upstream supply has switching noise above a few kilohertz, the PSRR rolls off; a ceramic output cap with low ESR helps maintain rejection at higher frequencies.
Enable, protection, and quiescent draw
An enable pin lets the regulator be shut down externally, dropping the supply current to the microamp range. Over-current and over-temperature protection are built in — the part folds back current during a fault and thermal-shuts down if the die exceeds the safe junction temperature. Quiescent current is 500 µA typical, with a maximum supply current of 800 µA.