Fixed 3.3V rail, 85mA capacity
The STMicroelectronics LDK715M33R is a single-output positive linear regulator delivering a fixed 3.3V at up to 85mA from a SOT-23-5 package. Maximum input voltage is 24V, with a maximum dropout of 1V at full load — the headroom between the input rail and 3.3V must stay above that dropout across the load range to keep the output in regulation.
PSRR profile and analog rail noise
Power-supply rejection ratio is 57dB at 100kHz, rolling off to 38dB at 1kHz — upstream switching noise above the crossover frequency passes through unless filtered ahead of the LDO. For an analog front-end powered from a noisy buck converter, this PSRR profile means the regulator attenuates 100kHz ripple by a factor of ~700, but lower-frequency 1kHz ripple by only ~80 — the input filter design matters more for the sub-10kHz band.
Package and rework consideration
Housed in an SC-74A / SOT-753 package (SOT-23-5 footprint), the part is a five-pin surface-mount device with a 0.95mm pitch — the exposed pad is small enough that hand rework with a hot-air station is straightforward, but the part has no visible pin-1 marker beyond the standard chamfer, so double-check orientation before placing.
Temperature grade and protection
Built-in over-current and over-temperature protection means the part survives a sustained short on the output without latching up or burning — the thermal foldback reduces current until the die cools, then the output recovers.