Fixed 5 V rail with 55 dB ripple rejection — the analog supply choice
The LM2931T-5.0 is a fixed 5 V output low-dropout regulator from Texas Instruments, delivering up to 100 mA with a maximum dropout of 0.3 V at full load.
100 mA output, 0.3 V dropout — headroom and load budget
Rated for 100 mA continuous output, the 0.3 V maximum dropout at that current means the input must stay above 5.3 V to maintain regulation. That 300 mV headroom is tight for a 5 V rail fed from a 6 V battery or a lightly loaded 5.5 V supply — budget the minimum input voltage with the same care as the output current. Quiescent current is 1 mA typical, rising to 15 mA maximum under supply-fault conditions. For always-on or battery-backed loads, that 1 mA floor is worth comparing against lower-Iq LDO families if standby power is the constraint.
Protection set and temperature grade — where it survives
On-chip protection covers over-temperature, reverse polarity, and short-circuit events — three failure modes common in automotive and industrial environments where the regulator sees a raw, unregulated bus.