STMicroelectronics LF33ABPT

Overview

LF33ABPT from STMicroelectronics is a 3.3 V, ±1% tolerance, 500 mA very low dropout (LDO) linear voltage regulator with logic-controlled shutdown, housed in a PENTAWATT-5 package. It delivers 3.3 V output at up to 500 mA load with only 0.2–0.35 V dropout at 200 mA and operates across –40°C to +125°C junction temperature. Its 50 µA quiescent current in OFF mode and 2.2 µF minimum output capacitance make it ideal for battery-powered microcontroller subsystems requiring standby power control.

For engineers reviewing the LF33ABPT datasheet, LF33ABPT pinout, LF33ABPT application, or LF33ABPT equivalent, key selection criteria include its 3.3 V fixed output, TTL-compatible enable input (Pin 2), 80 dB supply rejection at 120 Hz, 50 µV RMS output noise (10 Hz–100 kHz), and thermal shutdown/current limiting protection-critical for low-noise embedded power rails.

Technical Context

The LF33ABPT implements a PNP pass transistor architecture enabling ultra-low dropout operation, with internal current and thermal limiting ensuring robustness under fault conditions. Its logic-controlled shutdown (TTL-compatible INH pin) allows precise system-level power sequencing and partial-board standby without external circuitry.

It achieves stable regulation with only 2.2 µF ceramic output capacitance (ESR 0.1–10 Ω), eliminating need for large electrolytic capacitors. The device maintains ±1% output accuracy over temperature (–25°C to +85°C) and line/load variations, supporting precision analog and digital supply domains.

Key Specifications

Pinout & Package

PENTAWATT-5 (vertical mount, 5-pin) package with exposed tab for thermal dissipation; pin 1 = Input, pin 2 = Inhibit (TTL-compatible enable), pin 3 = Ground, pin 4 = Output, pin 5 = Bypass (not used in standard configuration).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar LDO regulator applications.

Compared with LD33CVTR and TLV73333PDBVR, the LF33ABPT uniquely combines 500 mA capability, TTL-enable functionality, ±1% accuracy, and integrated thermal/current protection in a thermally efficient PENTAWATT-5 package-making it optimal for automotive and industrial designs demanding reliability and controllability.

Availability

LF33ABPT is available at Aetrix Electronics and suitable for industrial PLC I/O modules, automotive body control units, portable medical sensor nodes, and smart home hub controllers requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LF33ABPT includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing microcontrollers, power management ICs, sensors, and analog components for industrial, automotive, and consumer markets.

The LF00 series-including LF33ABPT-is engineered specifically for low-noise, low-power, and battery-sensitive applications requiring high accuracy, ultra-low dropout, and logic-controlled enable functionality in harsh thermal environments.

FAQ

What is the minimum input voltage required for stable 3.3 V output at 500 mA?

The LF33ABPT requires a minimum input voltage of 3.7 V to maintain regulated 3.3 V output at 500 mA load, based on its maximum 0.7 V dropout specification under those conditions. At 200 mA, the dropout drops to 0.35 V, allowing stable operation from as low as 3.65 V input. Input must remain within the absolute maximum range of –0.5 V to 40 V.

Can the INH (Pin 2) be left floating, or must it be tied high/low?

Pin 2 (INH) must never be left floating-it has no internal pull-up or pull-down. For guaranteed ON operation, tie Pin 2 to VIN (≥2 V). For guaranteed OFF state, connect to GND (≤0.8 V). Floating may cause unpredictable oscillation or partial conduction, increasing power loss and thermal stress.

Is an input capacitor required, and what value is recommended?

Yes-an input capacitor is mandatory for stability and transient response. STMicroelectronics specifies a minimum 0.1 µF ceramic capacitor placed as close as possible to Pin 1 (IN) and Pin 3 (GND). For systems with long input traces or high source impedance, adding a 10 µF tantalum or aluminum electrolytic in parallel improves low-frequency ripple rejection.

Does the LF33ABPT require a heatsink in a PENTAWATT-5 package at 500 mA?

At 500 mA with 3.7 V input (0.4 V dropout), power dissipation is ~200 mW. With R_thJA = 50°C/W (PENTAWATT), junction rise is ~10°C above ambient-no heatsink needed in still air below 85°C ambient. For continuous 500 mA operation above 85°C ambient or in enclosed enclosures, mounting the exposed tab to a copper pour ≥4 cm² is recommended for thermal relief.