100 mA output — the BOM-fit ceiling
The LM317LZ/LFT3 is an adjustable positive voltage regulator from the LM317 family, but with a 100 mA output current ceiling — one-tenth the 1.5 A of the standard LM317. That current rating is the first filter: this part fits low-power rails where the load never exceeds 100 mA, not the higher-current bench supply or motor-drive bias rail. The output adjusts from 1.2 V up to 37 V using two external resistors, and the single regulator handles positive rail regulation only.
PSRR at 120 Hz — ripple rejection for analog rails
Power-supply rejection ratio is specified at 80 dB to 65 dB at 120 Hz, which means the regulator attenuates full-wave-rectified ripple by a factor of roughly 10,000 to 1,800. That matters when this part feeds a sensitive analog circuit — an op-amp supply, a small-signal front-end — where 120 Hz hum on the rail would couple into the signal path. The PSRR rolls off with frequency, so at higher switching-regulator ripple the rejection is lower; plan the input filter accordingly.
Through-hole TO-92-3 — board integration
The TO-92-3 (TO-226AA) through-hole package is the classic three-lead transistor outline — compact, hand-solderable, and fits standard 0.1-inch pitch prototyping boards. The 5 mA quiescent current is drawn regardless of load, so in a battery-powered design that standby current eats into the run-time budget. Protection features — overcurrent, overtemperature, short-circuit — are built in, so no external clamp diodes or foldback circuits are needed for basic survivability.