5V fixed LDO with 65dB PSRR at 120 Hz
The REG103UA-5 is a fixed 5V output LDO linear regulator from Texas Instruments, delivering up to 500 mA continuous current. Its 65 dB power supply rejection ratio at 120 Hz means it attenuates 120 Hz ripple from a rectified mains supply by a factor of roughly 1800 — critical for keeping analog supply rails clean in measurement or audio circuits where the line-frequency fundamental would otherwise couple into the signal path. Maximum dropout voltage is 0.28 V at the full 500 mA load, so the input rail needs to stay above 5.28 V across line and load transients to maintain regulation. Quiescent current is 0.7 mA typical, rising to 1.3 mA max at full supply — low enough for always-on rails in battery-backed equipment.
Industrial temperature grade and protection
Built-in over-current and over-temperature protection fold back the output under fault conditions; the regulator recovers automatically when the junction cools. An enable pin (active-high) allows the rail to be sequenced on and off, which is useful for power-rail order in multi-supply designs.
8-SOIC package and board integration
The output capacitor and input capacitor placement follow the usual LDO layout rules — the enable pin can be tied to Vin if sequencing is not needed. Supplied in tube packaging, suitable for hand-assembly or low-volume pick-and-place without reel changeover.