2.5V fixed rail for noise-sensitive analog and RF stages
The LP2985-25DBVT is a fixed 2.5V output LDO from the LP2985 series, delivering 150 mA continuous current in a 5-pin SOT-23-5 package. The fixed output eliminates the external resistor divider and the associated noise injection from the feedback node — a clean rail for the analog front-end or RF oscillator supply where a 1% tolerance 2.5V reference is needed without external trimming. A 3.3 V supply with 5% tolerance sits at 3.135 V minimum — enough headroom, but a 3.0 V rail would drop out at high load.
Temperature grade and supply chain
The wide range also means the dropout and output accuracy specs hold at the hot end, not just at 25°C.
PSRR and noise rejection in the 1kHz band
Power-supply rejection ratio is specified at 45 dB at 1 kHz. This is the mid-band rejection figure — the regulator attenuates 1 kHz ripple on the input by a factor of ~178. For a 100 mV p-p switching ripple at 1 kHz, the output sees about 0.56 mV p-p. The PSRR rolls off above the unity-gain crossover of the error amplifier, so higher-frequency noise (above ~100 kHz) passes through with less attenuation.
Protection and quiescent draw
Built-in protection covers over-current, over-temperature, and short-circuit events. The current-limit foldback keeps the die temperature within the SOA during a hard short. Quiescent current is 95 µA typical, rising to 2.5 mA maximum under full load — low enough for battery-powered sensors that spend most of their time in a light-load or shutdown state, where the Enable pin (active-high) cuts the supply current to near zero. Input voltage range extends to 16 V maximum, so the part tolerates a 12 V unregulated rail or a 5 V bus without an external pre-regulator. The 2.5 V fixed output at 150 mA suits low-voltage core rails for MCUs, RF transceivers, and sensor ASICs that need a quiet supply separate from the noisy digital rail.