Fixed 5 V LDO with 80 dB PSRR — the analog-rail choice
The Texas Instruments LM2931AM-5.0 is a fixed 5 V positive-output low-dropout regulator rated for 100 mA continuous output. The 0.3 V maximum dropout at 100 mA means the input can sag to 5.3 V before the output drops out of regulation — useful on a 5 V rail fed from a battery or a loosely regulated bus.
The 0.3 V dropout at 100 mA sets the minimum input-to-output headroom: a 5 V rail from a 5.3 V source works, but a 5.0 V input does not. The quiescent current is 15 mA typical — not a micropower LDO, but acceptable for always-on analog rails where the load current dominates the power budget. Protection covers over-temperature, reverse polarity, and short circuit, so the part survives a miswired bench or a downstream fault without latching up.