PSRR profile and signal-chain fit
The L4931ABDT50-TR delivers 70 dB of PSRR at 120 Hz, dropping to 55 dB at 10 kHz — this means it cleans line-frequency ripple well but passes higher-frequency switching noise from a downstream buck converter or digital load. For a sensitive analog front-end, add a post-filter LC stage above 10 kHz if the noise floor budget demands it.
Output and dropout — the headroom rule
Fixed 5 V output at 250 mA continuous, with a maximum dropout voltage of 0.8 V at full load. The input rail must stay above 5.8 V across the load range and temperature swing — below that, the output falls out of regulation. A 6 V or 7.5 V rail is the practical minimum for margin.
Temperature grade and deployment envelope
Rated for -40°C to 125°C operating junction temperature — this covers industrial enclosures and under-hood automotive ambient without derating. The DPAK (TO-252) tab soldered to a copper plane on the PCB pulls heat away; without a thermal via array under the tab, the effective RthJA rises and the 250 mA ceiling may need to be backed off above 85°C ambient.
Protection and quiescent draw
Built-in over-current and over-temperature protection — the regulator folds back current on a short or thermal event and auto-recovers when the fault clears. Quiescent current is 1 mA typical, with a maximum supply current of 6 mA. Not a micropower LDO, but the Iq is reasonable for always-on automotive modules or industrial sensor nodes that don't sleep below 100 µA.