STMicroelectronics LF18CPT

Overview

LF18CPT from STMicroelectronics is a 1.8 V fixed-output, 500 mA very low dropout (LDO) linear regulator in TO-220FP package with logic-controlled shutdown (TTL-compatible enable), ±2% output voltage accuracy at 25°C, 0.7 V dropout at 200 mA, 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 1.8 V supply for microcontroller I/O or low-voltage logic.

For engineers reviewing the LF18CPT datasheet, LF18CPT pinout, LF18CPT application, or LF18CPT equivalent, key selection considerations include dropout performance at 200–500 mA load, shutdown leakage (<100 µA), thermal resistance (R_thJC = 5 °C/W), stability with 2.2 µF ceramic output capacitor, and compatibility with 0.8–2.0 V logic-level enable control.

Technical Context

The LF18CPT implements a PNP pass transistor architecture enabling ultra-low dropout voltage (0.7 V at 200 mA) and high PSRR (82 dB at 120 Hz). Its internal circuit integrates thermal shutdown, current limiting, and a dedicated TTL-compatible enable input (Pin 2) that places the device in <100 µA standby when driven low.

It operates across –40 to +125°C junction temperature and supports input voltages from 3.0 V to 16 V. The regulator achieves stability with only 2.2 µF output capacitance (ESR 0.1–10 Ω), eliminating need for large electrolytic capacitors and reducing board space in space-constrained designs.

Key Specifications

Pinout & Package

LF18CPT is housed in a 5-pin TO-220FP package with exposed tab (thermal pad) connected to Pin 3 (GND). Pin 1 = Input (VI), Pin 2 = Enable (EN), Pin 3 = Ground (GND), Pin 4 = Output (VO), Pin 5 = Bypass (BP).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LD1117S18TR and TPS7A0518PDQNR, LF18CPT uniquely balances 500 mA output, 0.7 V dropout, integrated TTL enable, and TO-220FP thermal robustness-making it optimal for industrial and automotive LDO applications demanding both performance and reliability under sustained load.

Availability

LF18CPT is available at Aetrix Electronics and suitable for portable medical sensors, industrial PLC I/O modules, and automotive body control units requiring stable component supply with long-term manufacturability and AEC-Q100-aligned qualification.

Supply support for LF18CPT 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 silicon solutions for automotive, industrial, and consumer markets since 1987.

The LF00 series was developed specifically for low-noise, low-power, and battery-critical applications-emphasizing ultra-low dropout, micropower shutdown, and wide-input-voltage operation in ruggedized power packages.

FAQ

What is the minimum input voltage required for LF18CPT to maintain regulation at 500 mA?

The LF18CPT requires VI ≥ VO + V_d = 1.8 V + 0.7 V = 2.5 V to sustain regulation at 200 mA; at 500 mA, dropout rises to 0.7 V (typ.) per Table 5, so minimum input remains 2.5 V. However, full 500 mA output is guaranteed only when VI ≥ 3.0 V per electrical characteristics.

Can LF18CPT operate without the bypass (BP) pin connected?

Yes. Pin 5 (BP) is optional: leaving it open degrades PSRR above 1 kHz but maintains full DC regulation and stability. For best noise rejection in sensitive analog circuits, connect a 10 nF ceramic capacitor from BP to GND per Figure 2 in the datasheet.

Is the TO-220FP package lead-free and RoHS-compliant?

Yes. LF18CPT TO-220FP is manufactured per STMicroelectronics' standard RoHS-compliant process, with lead-free terminations and halogen-free molding compound, meeting EU Directive 2011/65/EU and JEDEC J-STD-020 moisture sensitivity level MSL3.

Does LF18CPT require an input capacitor, and what value is recommended?

Yes. A 0.1 µF ceramic capacitor must be placed between Pin 1 (VI) and Pin 3 (GND), located within 5 mm of the device. This minimizes high-frequency input impedance and prevents oscillation during fast load transients, as specified in Section 3 (Electrical Characteristics) and Figure 2 (Test Circuit).