80 dB PSRR at 1 kHz — the analog-rail LDO
The Microchip MIC5317-3.3YMT-TR is a single-output, fixed 3.3 V positive LDO rated for 150 mA continuous output. Its headline feature is the PSRR curve: 80 dB at 1 kHz, rolling off to 65 dB at 10 kHz, which puts it in the low-noise regulator class suitable for powering analog front-ends, ADC reference buffers, or RF VCO supplies where the upstream switching regulator needs suppression. Dropout is specified at 0.31 V maximum at the full 150 mA load, so the input rail needs at least 3.61 V to hold regulation. Quiescent current sits at 39 µA typical — not the lowest for battery-idle, but reasonable for a part that prioritises PSRR over micropower.
Thermal and package — 1×1 mm UDFN with exposed pad
The package is a 4-lead UDFN measuring 1×1 mm with an exposed pad. The exposed pad also serves as the ground return — the PCB layout must connect it directly to the ground plane with multiple vias to keep inductance low.
Protection and control
On-chip protection includes over-current and over-temperature shutdown. No reverse-current protection is listed, so if the output can rise above the input (e.g., a backup battery), an external Schottky or series diode is needed.