Active production — 300mA fixed-output LDO for noise-sensitive rails
The MIC5318-3.3YMT-TR is an active-production LDO from Microchip Technology, delivering a fixed 3.3V output at 300mA from a maximum 6V input rail. With a maximum dropout of 0.2V at full load, the input rail needs only 3.5V to maintain regulation — a 200mV headroom margin that fits tightly regulated 3.6V or 5V supplies. The -40°C to 125°C operating range covers industrial floor and under-hood automotive ambient without derating the output current.
75dB PSRR across the audio band — what it means for supply noise
PSRR measures 75dB at 1kHz and rolls to 55dB at 20kHz — this is the audio-frequency band where switching-regulator ripple and digital clock feedthrough are hardest to filter. At 1kHz, 75dB rejection means a 100mVpp input ripple is attenuated to roughly 18µVpp at the output — clean enough for a 16-bit ADC reference or a Class-D pre-driver supply. The 150µA quiescent current keeps the regulator's own draw low enough for always-on sensor rails that wake on an interrupt, though it is not an ultra-low-Iq part for continuous battery monitoring.
6-TMLF package — thermal pad and layout notes
The 6-TMLF package (1.6x1.6mm body) has an exposed pad that must be soldered to a PCB copper plane for thermal dissipation — the datasheet's RθJA figure assumes a 2-layer board with a 1-inch² pad. Surface-mount assembly with the Enable pin (active-high) lets the regulator be gated by a GPIO or power-good signal; unused Enable should be tied to Vin to keep the output on. Over-current and over-temperature protection are built in — the regulator folds back current on a short and shuts down above the thermal limit, then auto-recovers when the die cools.