STMicroelectronics LF18ABPT

Overview

LF18ABPT from STMicroelectronics is a 1.8 V fixed-output, very low dropout (LDO) linear regulator in TO-220FP package with logic-controlled shutdown, delivering up to 500 mA output current, 0.7 V dropout at 200 mA, ±1% output voltage accuracy at 25°C, and 50 µA quiescent current in OFF mode. It serves as a local power rail regulator in battery-powered embedded systems requiring stable low-noise supply under dynamic load and thermal stress.

For engineers reviewing the LF18ABPT datasheet, LF18ABPT pinout, LF18ABPT application, or LF18ABPT equivalent, key selection criteria include its 1.8 V output tolerance, shutdown control compatibility with TTL logic, thermal performance in TO-220FP (R_thJC = 5°C/W), stability with only 2.2 µF output capacitance, and operation across –40°C to +125°C junction temperature.

Technical Context

The LF18ABPT implements a PNP pass transistor architecture enabling ultra-low dropout voltage and high PSRR (82 dB at 120 Hz). Its internal shutdown circuit accepts TTL-compatible logic levels (V_IL ≤ 0.8 V, V_IH ≥ 2 V) on Pin 2, allowing system-level power gating without external FETs or level shifters.

It integrates thermal foldback and current limiting for safe operation under overload or short-circuit conditions, and achieves 50 µV RMS output noise (10 Hz–100 kHz) with minimal external components-only a 0.1 µF input capacitor and 2.2 µF output capacitor with ESR between 0.1 Ω and 10 Ω are required for stability.

Key Specifications

Pinout & Package

LF18ABPT is housed in a 5-pin TO-220FP package with heat sink tab (Pin 3), offering enhanced thermal performance (R_thJC = 5°C/W) over standard TO-220. The pinout supports direct integration into compact power sections with minimal layout complexity.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LD1117S18TR and TPS7A0518PDBVR, LF18ABPT uniquely balances 500 mA output, TTL-compatible shutdown, and 0.7 V dropout in a thermally robust TO-220FP package-making it optimal for industrial and automotive applications demanding both performance and ruggedness.

Availability

LF18ABPT is available at Aetrix Electronics and suitable for industrial PLC I/O modules, automotive body control units, portable medical sensor hubs, and wireless edge nodes requiring stable component supply across extended temperature and long product lifecycles.

Supply support for LF18ABPT 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, designing and manufacturing analog, MCU, power, and sensing solutions for industrial, automotive, and consumer markets.

The LF00 series was developed specifically for low-noise, low-power local regulation in battery-constrained and thermally demanding environments-emphasizing dropout voltage, quiescent current, and ease of stabilization.

FAQ

What is the minimum input voltage required for LF18ABPT to maintain 1.8 V output at 500 mA?

The minimum input voltage is 3.0 V, derived from the specified operating input voltage range (3.0–16 V) and maximum dropout of 0.7 V at 200 mA. At 500 mA, dropout rises to 1.0 V per typical characterization curves in the LF00 series datasheet, so 2.8 V input would be insufficient; 3.0 V is the guaranteed functional lower bound.

Can LF18ABPT be used without the shutdown pin connected?

Yes-Pin 2 (SHDN) may be left unconnected or tied to IN (for permanent ON) or GND (for permanent OFF). When floating, internal pull-down ensures default OFF state (50 µA I_Q). For reliable ON operation, connect Pin 2 to IN via 10 kΩ resistor or directly if VI ≤ 6 V.

Is a heatsink required for LF18ABPT delivering 500 mA at 125°C ambient?

No discrete heatsink is required if PCB copper area provides ≥25 cm² of 2-oz copper connected to Pin 3 (TAB). With R_thJA = 60°C/W (TO-220FP), 500 mA at 125°C ambient yields ~95°C junction rise above ambient-well within the 125°C max rating. Thermal simulation or IR imaging is recommended for final layout validation.

Does LF18ABPT require an input capacitor, and what value is recommended?

Yes-a 0.1 µF ceramic capacitor is mandatory at the IN pin, placed within 5 mm of the device. This stabilizes the internal control loop against input impedance variations and suppresses high-frequency noise from upstream converters. Larger values (e.g., 10 µF) may be added in parallel for bulk filtering but do not replace the 0.1 µF requirement.