Package and board integration — 1.6x1.6 mm TMLF
The MIC5309YMT-TR comes in a 6-TMLF® package measuring 1.6x1.6 mm with an exposed pad (6-UFDFN). The exposed pad is the primary thermal path; the datasheet's RθJA figure assumes a certain PCB copper area. If your layout cheats the pad copper, derate the output current or accept a higher junction temperature.
Dropout and headroom — 200 mV at full load
Maximum dropout is 0.2 V at 300 mA output. Output is adjustable from 0.8 V minimum to 2 V maximum using an external resistor divider. This covers the core voltages for many low-power MCUs and RF SoCs that need a clean 1.2 V or 1.8 V rail.
PSRR — what 90 dB at 1 kHz actually means
Power supply rejection ratio is 90 dB typical at 1 kHz, rolling off to 70 dB at the same frequency — this is the low-frequency band where switching regulator ripple lives. A 100 mVpp ripple on the input at 1 kHz gets attenuated to roughly 3 µVpp at the output. Above 100 kHz the PSRR drops further, so any high-frequency noise from a boost converter ahead of this LDO needs a ferrite bead or additional filtering.
Protection and control — enable pin and fault handling
The enable pin lets a GPIO or power sequencer turn the regulator on and off — useful for sequencing multiple rails or putting the load into a low-power sleep state. Built-in over-current and over-temperature protection means the part survives a shorted output or a stalled fan without external foldback circuitry.