120 mA LDO with 0.12 V dropout — the field-swap call
The MAX8863TEUK+T is a single-output positive LDO regulator from Analog Devices, rated for 120 mA continuous output. The headline number that matters in a tight-rail design is the dropout: 0.12 V maximum at 50 mA load. That means a 3.3 V rail stays regulated with the input down to about 3.42 V — useful for battery-powered gear or post-regulator stages where every millivolt of headroom counts. Output is adjustable from 1.25 V up to the 6.5 V input max, or you can use the fixed 3.15 V option if you do not need the resistor divider. The SOT-23-5 package is small enough for a field kit — orientation is obvious with the pin-1 dot, and rework with a standard iron is straightforward.
62 dB PSRR at 300 Hz — what it buys you
The PSRR is 62 dB at 300 Hz. That is the ripple-rejection figure for the mains-frequency band and its harmonics. If you are powering an op-amp or a small ADC from this rail, that 62 dB knocks down a 100 mV ripple to about 50 µV at the output — clean enough for a 12-bit converter on a 3.3 V reference. The quiescent current sits at 150 µA typical, with a max supply current of 80 µA, so it does not waste the battery between bursts.
Protection set and temperature range
The part packs over-current, over-temperature, reverse polarity, and short-circuit protection — all on-chip, no external clamp diodes needed for the basic case.