3V fixed rail for noise-sensitive analog supplies
The LD2981ABM30TR is a 100 mA fixed-output LDO from STMicroelectronics, delivering a regulated 3 V rail from an input up to 16 V. The 0.375 V max dropout at full load means the input needs only 3.375 V to hold regulation — useful when the pre-regulator rail sags under load. PSRR is 63 dB at 1 kHz, which attenuates switching noise from a preceding buck converter by roughly 1000× at that frequency. For a 3 V analog supply feeding an op-amp or ADC reference, this keeps ripple off the sensitive rail without a post-filter.
Dropout and quiescent current for always-on rails
Quiescent current is 150 µA typical — not the lowest in the class, but acceptable for a 100 mA LDO where the load current dominates the power budget. The 2.6 mA max supply current includes the pass-element drive; at light loads the Iq is the main draw. The enable pin (active-high) lets the system shut the 3 V rail entirely, cutting the quiescent draw to near zero when the downstream circuit sleeps. Over-current and over-temperature protection are built in — the part folds back current on a fault and recovers when the junction cools.
Industrial temperature and SOT-23-5 footprint
The SOT-23-5 (SC-74A) package is a standard 5-pin footprint shared by many LDOs — the pinout (GND, EN, IN, OUT, NC) is common enough that a layout swap to a second-source part is straightforward. Available on tape and reel or cut tape. The reel quantity is not specified here, but the TR suffix indicates standard 7-inch reel packaging for pick-and-place. Store the reels dry — the SOT-23 is not moisture-sensitive per JEDEC Level 1, but the tape itself should stay in the sealed bag until the line runs.