STMicroelectronics LF50CDT

Overview

LF50CDT from STMicroelectronics is a 5 V fixed-output, 500 mA low-dropout linear regulator in TO-220FP package with logic-controlled shutdown (TTL-compatible enable), 0.4 V typical dropout at 500 mA, ±2% output voltage accuracy at 25°C, and operation from −40°C to +125°C junction temperature. It delivers stable local regulation for battery-powered microcontroller subsystems requiring low quiescent current (50 µA in OFF mode) and minimal external components.

For engineers reviewing the LF50CDT datasheet, LF50CDT pinout, LF50CDT application, or LF50CDT equivalent, this page provides verified electrical specifications, thermal performance data, real-world use cases in portable instrumentation and automotive body control modules, and validated alternative parts with documented functional trade-offs.

Technical Context

The LF50CDT implements a PNP pass transistor architecture enabling ultra-low dropout (0.4 V typ. at 500 mA) and high PSRR (76 dB at 120 Hz). Its internal current and thermal limiting protect against overload and fault conditions without external circuitry.

It features a dedicated TTL-compatible shutdown input (pin 2) that enables system-level power sequencing and standby mode control. The device stabilizes with only a 2.2 µF ceramic output capacitor (ESR 0.1–10 Ω), reducing board area and cost versus traditional LDOs requiring larger electrolytics.

Key Specifications

Pinout & Package

LF50CDT is housed in a TO-220FP (Full Pack) thermally enhanced 5-pin package with isolated tab, offering R_thJC = 5°C/W and R_thJA = 60°C/W. Pin 1 = Input, Pin 2 = Shutdown (TTL-compatible), Pin 3 = Ground, Pin 4 = Output, Pin 5 = Tab (connected to ground).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LDL115M50R and LDL212P50R, LF50CDT uniquely balances high output current (500 mA), integrated shutdown control, and robust thermal performance in TO-220FP - making it optimal for industrial and automotive subsystems where both power and controllability matter.

Availability

LF50CDT is available at Aetrix Electronics and suitable for portable medical devices, automotive body electronics, industrial PLC expansion cards, and smart energy meters requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LF50CDT 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, specializing in power management, microcontrollers, sensors, and automotive ICs with broad industrial and automotive qualification coverage.

The LF00 series was designed specifically for low-noise, low-power local regulation in battery-operated and thermally constrained systems - emphasizing ultra-low dropout, minimal external components, and wide-temperature reliability.

FAQ

What is the minimum input voltage required for LF50CDT to maintain 5 V output at 500 mA?

The LF50CDT requires a minimum input voltage of 5.4 V to sustain 5 V output at 500 mA load, based on its typical 0.4 V dropout voltage. At higher temperatures or worst-case process corners, the dropout may reach 0.7 V, so 5.7 V is recommended for margin in production designs.

Can LF50CDT be used without the shutdown pin connected?

Yes - leaving pin 2 (SHDN) open or tying it to VIN places the device permanently in ON mode. However, doing so forfeits the 50 µA OFF-mode quiescent current benefit. For always-on applications, this is acceptable; for battery systems, a pull-up resistor to VIN is preferred over floating.

Is an input capacitor required for stable operation?

An input capacitor is strongly recommended: ≥0.1 µF ceramic placed as close as possible to pins 1 (IN) and 3 (GND). While not strictly mandatory for basic regulation, it prevents instability from source impedance and suppresses high-frequency noise coupling into the regulator's feedback path.

Does LF50CDT require a heatsink in TO-220FP package at 500 mA?

A heatsink is not required for typical ambient conditions (<50°C) with adequate PCB copper (≥2 cm² 2-oz copper connected to pin 5 tab). At 500 mA and 12 V input, power dissipation is ~3.5 W; with R_thJA = 60°C/W, junction rise is ~210°C above ambient - so PCB thermal design is essential. Forced air or small clip-on heatsink is advised for >40°C ambient or sustained full load.