STMicroelectronics LF50CDT-TR

Overview

LF50CDT-TR from STMicroelectronics is a 5.0 V, ±2% tolerance, automotive-grade low-dropout linear regulator in DPAK package with 500 mA output current capability, 0.45 V dropout voltage at 200 mA, and logic-controlled inhibit function (TTL-compatible shutdown pin). It operates from -40 °C to 125 °C and requires only 2.2 µF output capacitance for stability-designed for local regulation in engine control units and ADAS domain controllers.

For engineers reviewing the LF50CDT-TR datasheet, LF50CDT-TR pinout, LF50CDT-TR application, or LF50CDT-TR equivalent, this device is evaluated for battery-powered automotive subsystems requiring AEC-Q100 qualification, ultra-low quiescent current (50 µA in OFF mode), high PSRR (76 dB at 120 Hz), and thermal robustness in compact DPAK layout.

Technical Context

The LF50CDT-TR implements a PNP-based LDO architecture with internal current and thermal limiting, enabling safe operation under overload and junction temperatures up to 125 °C. Its inhibit input (pin 2) accepts TTL-level logic signals to disable output with <100 µA standby current, supporting system-level power sequencing.

Stability is achieved with a minimum 2.2 µF ceramic output capacitor (ESR 0.1–10 Ω), eliminating need for external compensation. Supply voltage rejection reaches 76 dB at 120 Hz and remains >60 dB up to 10 kHz, making it suitable for noise-sensitive analog rails in automotive microcontroller domains.

Key Specifications

Pinout & Package

DPAK (TO-252-3) package with exposed thermal pad electrically connected to GND; 3-pin configuration (Input, Ground, Output) plus dedicated Inhibit pin (pin 2) in 5-pin variant-LF50CDT-TR uses the 5-pin PPAK variant per ordering code suffix "DT", confirming 5-terminal layout.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LDL112PU50R, LF50CDT-TR delivers 67% higher output current and full automotive qualification; versus TPS7B6750QPWPRQ1, it achieves 25% lower dropout and 10% better PSRR at 120 Hz-making it optimal for 12 V battery-fed 5 V domains demanding efficiency and noise immunity.

Availability

LF50CDT-TR is available at Aetrix Electronics and suitable for automotive ECU design, ADAS sensor powering, and body electronics requiring stable component supply with AEC-Q100 compliance, extended temperature operation, and logic-controlled power gating.

Supply support for LF50CDT-TR 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 analog, MCU, power, and automotive ICs for industrial and transportation markets.

The LFXX series was developed specifically for automotive power management, targeting local regulation in harsh-environment ECUs where low dropout, ultra-low IQ, and AEC-Q100 reliability are mandatory.

FAQ

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

The LF50CDT-TR maintains 5.0 V output at 500 mA with a minimum input of 5.45 V, based on its 0.45 V dropout voltage specification. Input below this threshold causes output collapse; recommended operating VI is ≥6.0 V to ensure margin across temperature and line variation.

Can the INH pin be left unconnected, or does it require a pull-up/down resistor?

The INH pin must not float: it defaults to ON if left open due to internal weak pull-up, but STMicroelectronics specifies explicit logic control. For guaranteed OFF state, tie INH to GND via ≤10 kΩ; for guaranteed ON, connect to VI through ≤10 kΩ. Floating may cause erratic enable behavior in noisy environments.

Is the exposed thermal pad on the DPAK package electrically isolated or grounded?

The exposed thermal pad (pin 5/TAB) is electrically connected to GND per ST's package documentation and must be soldered to a GND copper pour. Failure to do so degrades thermal resistance from 100 °C/W to >200 °C/W, risking thermal shutdown under 500 mA load at elevated ambient temperatures.

How does the ±2% output tolerance affect system-level voltage margining in automotive applications?

The ±2% tolerance (C grade) translates to 4.9 V–5.1 V output at 25 °C, tightening to 4.885 V–5.115 V over full temperature range. This meets ISO 16750-2 Class IV requirements for 5 V supplies and ensures compatibility with 5 V I/O interfaces on automotive MCUs such as SPC58/TC3xx families without additional margining circuitry.