3.3 V fixed LDO — what the ratings mean for your rail
The Texas Instruments LP3985IM5X-3.3/NOPB is a single-output, fixed 3.3 V positive LDO regulator rated for 150 mA continuous output. It comes in a SOT-23-5 package with an enable pin for on/off control. The part is designed for noise-sensitive analog and mixed-signal rails where supply rejection matters across the audio band. PSRR starts at 50 dB at 1 kHz and rolls to 40 dB at 10 kHz. That 10 dB drop across one decade is typical for a low-Iq LDO; if your load draws switching noise above 10 kHz, plan for additional post-filter capacitance or a higher-PSRR regulator. Quiescent current is 150 µA typical, supply current maximum 250 µA — low enough for battery-operated gear but not the ultra-low-Iq tier (sub-10 µA) you would pick for always-on wearables. The 150 µA Iq is a reasonable trade-off for the PSRR and dropout figures. Operating temperature spans -40°C to 125°C, which qualifies it for automotive under-hood, industrial motor drives, and outdoor telecom enclosures — not just commercial indoor boards.
Protection and control — built-in, no external watchdog needed
Over-current, over-temperature, and short-circuit protection are integrated. No external current-limit resistor or thermal shutdown circuit required. The enable pin lets a GPIO or supervisor sequence the rail on and off.
Sourcing and lifecycle — active, no LTB risk
No last-time-buy notice or obsolescence risk for current BOM commitments. ROHS3 compliant.