Fixed 1.8V LDO for noise-sensitive rails
The Micrel MIC5302-1.8YMT-TR is a single-output, positive fixed-voltage LDO regulator delivering 150 mA at 1.8 V. Its key analog characteristic is the PSRR: 65 dB at 1 kHz, rolling off to 42 dB at 20 kHz, which matters when you are cleaning up a switching regulator's ripple on an analog or RF supply rail. The maximum dropout voltage is 0.1 V at the full 150 mA load, so a 3.3 V input rail with a 0.5 V margin still holds regulation through a cold-crank event. Quiescent current sits at 120 µA, making it a reasonable fit for always-on peripherals that cannot tolerate the noise of a DC-DC converter.
Dropout and headroom budget
With a maximum dropout of 0.1 V at 150 mA, this LDO needs only 1.9 V input to maintain a clean 1.8 V output. For a 3.3 V to 1.8 V conversion, the headroom is 1.5 V — plenty for PSRR performance, but the dropout figure is what you check when the input sags during a brownout or battery discharge. The 120 µA quiescent current is the current the regulator burns just to stay alive; it does not scale with load, so at light loads (tens of µA) the Iq dominates the efficiency.
Package and thermal: 4-TMLF (1.2x1.6 mm)
It is a tiny land-grid array — not a leaded package — so the PCB footprint must match the 4-TMLF land pattern exactly. At 150 mA output and 1.5 V dropout, dissipation is 225 mW, which is manageable with a good thermal via stitch.
Built-in over-current and over-temperature protection are standard for this class of LDO. An Enable pin allows the regulator to be shut down externally, pulling the output to high impedance and reducing the supply current to near zero — useful for sequencing or power-save modes in battery-powered designs. The output is fixed at 1.8 V, so no external resistor divider is needed; just the input and output capacitors per the datasheet recommendation.