STMicroelectronics LF50ABDT

Overview

LF50ABDT from STMicroelectronics is a 5.0 V, ±1% fixed-output low-dropout linear regulator in TO-220FP package with logic-controlled shutdown, 0.2–0.7 V dropout (IO = 200–500 mA), 500 mA output current capability, and 50 µA typical quiescent current in OFF mode. It serves as a local power supply for microcontroller cores, sensor interfaces, and battery-backed subsystems requiring stable low-noise voltage under tight thermal constraints.

For engineers reviewing the LF50ABDT datasheet, LF50ABDT pinout, LF50ABDT application, or LF50ABDT equivalent, key selection considerations include its 0.2 V dropout at 200 mA, ±1% output accuracy over temperature, TTL-compatible enable input (pin 2), 80 dB PSRR at 120 Hz, and compatibility with only 2.2 µF ceramic output capacitance for stability.

Technical Context

The LF50ABDT implements a PNP pass transistor architecture enabling ultra-low dropout operation and internal current/thermal limiting without external components. Its shutdown control pin (TTL-compatible, 0.8 V low / 2 V high) enables system-level power sequencing and standby mode activation.

Designed for operation across –40°C to +125°C junction temperature, it maintains ±1% output voltage accuracy (25°C) and ±2% over –25°C to +85°C ambient, with line regulation of ≤25 mV and load regulation ≤25 mV - all verified with 2.2 µF ESR-tolerant output capacitor (0.1–10 Ω).

Key Specifications

Pinout & Package

LF50ABDT is housed in a TO-220FP (Full Pack) thermally enhanced 5-pin package with isolated tab, optimized for PCB heat sinking via mounting screw. Pin 1 = Input, Pin 2 = Shutdown (TTL-compatible), Pin 3 = Ground, Pin 4 = Output, Pin 5 = Bypass (not used in standard configuration; tied to ground per datasheet Figure 1).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LDL112P50R and LDL212P50R, LF50ABDT delivers 500 mA output, integrated TTL shutdown, and superior thermal performance in TO-220FP - making it optimal for higher-power, thermally demanding, or system-controlled power management roles.

Availability

LF50ABDT is available at Aetrix Electronics and suitable for automotive body electronics, industrial PLC I/O modules, portable medical sensor hubs, and smart energy meter subsystems requiring stable component supply across extended temperature and long product lifecycles.

Supply support for LF50ABDT 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 microcontrollers, power management ICs, sensors, and automotive-grade analog products.

The LF00 series was developed specifically for low-noise, low-power, and battery-critical applications - emphasizing ultra-low dropout, minimal quiescent current, and robust thermal behavior in industrial and automotive environments.

FAQ

What is the minimum input voltage required for regulation at full 500 mA load?

The LF50ABDT requires VI ≥ VO + Vd, where Vd = 0.7 V max at 500 mA (per Table 19). With VO = 5.0 V, minimum input is 5.7 V. Operation below this causes dropout and unregulated output. At 200 mA, Vd drops to 0.35 V max, allowing regulation from 5.35 V.

Can Pin 5 (Bypass) be left floating?

No. Pin 5 is an internal NC terminal but must be connected to ground per ST's layout guidelines (Figure 1, page 3). Floating Pin 5 risks instability or increased noise due to parasitic coupling; grounding ensures predictable EMI performance and thermal path integrity.

Is the 2.2 µF output capacitor mandatory, or can larger values improve transient response?

The 2.2 µF value is the minimum required for stability with ESR 0.1–10 Ω. Larger capacitors (e.g., 10 µF) are permitted and improve load-transient response, but do not reduce dropout or noise. Exceeding 10 µF may require rechecking phase margin if ESR falls below 0.1 Ω.

How does the LF50ABDT behave during thermal shutdown?

When junction temperature exceeds ~165°C, internal thermal protection disables the pass transistor, dropping output to near zero volts. The device automatically recovers once TJ falls below ~145°C hysteresis. During shutdown, quiescent current remains at ~50 µA, preserving battery charge in fault conditions.