Fixed 5V rail for noise-sensitive analog supplies
The LP2981-50DBVT is a fixed 5V output LDO from Texas Instruments, delivering 100 mA from a SOT-23-5 package. Its 63 dB PSRR at 1 kHz makes it a strong candidate for cleaning up a 5V rail feeding analog front-ends, ADCs, or sensor bias circuits where ripple from a switching pre-regulator needs suppression. Maximum dropout is 0.37 V at full load, so a 5.37 V input rail is enough to keep the output in regulation across the full 100 mA range. The 95 µA quiescent current is moderate for a 100 mA LDO — not micropower, but low enough to avoid thermal issues in the SOT-23-5 footprint at moderate loads.
Package, pinout, and board-fit considerations
The LP2981-50DBVT comes in the SOT-23-5 (SC-74A) package — five pins, 0.95 mm pitch, 2.9 mm body. The Enable pin (active high) lets the system power down the regulator to near-zero draw when the 5V rail is not needed. Protection features include over-current, over-temperature, and short-circuit shutdown, all integrated. Input voltage range extends to 16 V, giving headroom for 12 V or 9 V rails. The part is ROHS3 compliant.