200 mA fixed 5 V rail for noise-sensitive loads
The STMicroelectronics LDK220PU50R is a single-output positive LDO regulator delivering a fixed 5 V at up to 200 mA. It belongs to the LDK220 family and is housed in a 6-XFDFN package (1.2x1.3 mm DFN), suited for space-constrained boards where a clean analog or digital supply rail is needed. PSRR runs 55 dB at 120 Hz down to 50 dB at 10 kHz, which means it knocks down low-frequency ripple from a mains-derived rectifier and still holds decent rejection into the switching-noise band. For a 5 V rail feeding a sensor front-end or a quiet ADC reference, that keeps the supply noise out of the signal chain.
Dropout, quiescent draw, and protection
Maximum dropout voltage is 0.35 V at the full 200 mA load, so the input rail needs at least 5.35 V to maintain regulation. On-chip protection includes over-current and over-temperature shutdown. The 6-DFN package with a 1.2x1.3 mm footprint is a small land pattern — the exposed pad underneath needs a thermal via to the ground plane to keep the junction temperature in check at high ambient and full load.