Fixed 5 V rail for noise-sensitive loads
The onsemi LM2931AMX-5.0 is a single-output positive LDO regulator delivering a fixed 5 V at up to 100 mA.
Dropout and headroom
Maximum dropout is 0.3 V at the full 100 mA load, so the input rail needs to stay above 5.3 V to hold regulation. That is tight enough to run off a 6 V or 7.5 V unregulated bus without wasting power as heat, but not low enough for a 5 V input — plan for at least 5.5 V minimum at the input pin under worst-case load and temperature.
Protection that survives a field swap
Built-in over-temperature shutdown, reverse polarity protection, and short-circuit current limiting mean this regulator can take the abuse of a miswired battery connection or a hot-swap glitch without dying. For a field-service repair, that is the difference between swapping the part once and coming back next week.
Obsolete — sourcing the BOM line
The LM2931AMX-5.0 is listed as obsolete.