STMicroelectronics LF18CDT

Overview

LF18CDT from STMicroelectronics is a 1.8 V fixed-output, 500 mA low-dropout linear regulator in TO-220FP package with logic-controlled shutdown (pin 2), 0.7 V dropout at 200 mA, ±2% 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 portable instrumentation requiring stable low-noise bias under variable load and thermal conditions.

For engineers reviewing the LF18CDT datasheet, LF18CDT pinout, LF18CDT application, or LF18CDT equivalent, this page delivers verified electrical specs, thermal resistance data (R_thJC = 5°C/W), shutdown timing behavior, stability requirements (2.2 µF ceramic output cap), and real-world substitution guidance for industrial embedded systems design.

Technical Context

The LF18CDT implements a PNP pass transistor architecture enabling ultra-low dropout operation and high PSRR (82 dB at 120 Hz). Its internal current and thermal limiting protect against overload and junction overheating during transient conditions.

Shutdown is TTL-compatible: logic low ≤0.8 V on pin 2 forces regulator OFF with 50 µA standby current; logic high ≥2 V enables regulation. The device operates across –40°C to +125°C junction temperature and requires only a 2.2 µF output capacitor with ESR between 0.1 Ω and 10 Ω for stability.

Key Specifications

Pinout & Package

LF18CDT uses the TO-220FP (Full Pack) 5-pin package with exposed tab for thermal dissipation. Pin 1 = Input, Pin 2 = Shutdown Control (TTL-compatible), Pin 3 = Ground, Pin 4 = Output, Pin 5 = Bypass (not used in standard configuration; tied to ground or left open per design).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar low-dropout regulator applications.

Compared with LD1117S18TR and TPS7A0518PDBVR, LF18CDT uniquely balances 500 mA output, 0.7 V dropout, integrated shutdown, and TO-220FP thermal performance-making it optimal for mid-power industrial and automotive modules where both current delivery and controllability matter.

Availability

LF18CDT is available at Aetrix Electronics and suitable for portable medical devices, automotive body electronics, industrial IoT edge nodes, and handheld test equipment requiring stable component supply with long-term manufacturability.

Supply support for LF18CDT 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, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The LF00 series was developed specifically for low-noise, low-power linear regulation in battery-critical and thermally demanding applications-emphasizing dropout minimization, shutdown control, and wide-temperature robustness.

FAQ

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

The LF18CDT requires a minimum input voltage of 2.5 V to maintain regulation at 500 mA output, based on its maximum dropout specification of 0.7 V at 200 mA and typical behavior scaling to ~0.9 V at 500 mA per thermal and process characterization in the datasheet.

Can Pin 5 (Bypass) be left floating in a standard application?

Yes, Pin 5 may be left unconnected in basic configurations, but STMicroelectronics recommends connecting it to ground via a 10 nF ceramic capacitor to improve PSRR above 10 kHz-particularly beneficial in mixed-signal systems with switching noise sources.

Does the LF18CDT require an input capacitor, and if so, what value?

Yes-an input bypass capacitor of at least 0.1 µF ceramic, placed as close as possible to Pins 1 and 3, is mandatory to ensure stability and suppress high-frequency noise from upstream sources, as confirmed in the test circuits and layout guidelines of the official datasheet.

How does thermal resistance differ between TO-220FP and PENTAWATT packages for the LF00 series?

For the LF00 series, TO-220FP has R_thJC = 5°C/W and R_thJA = 60°C/W, while PENTAWATT has R_thJC = 3°C/W and R_thJA = 50°C/W-meaning PENTAWATT offers slightly better junction-to-case conduction but both require external heatsinking for >1 W power dissipation.