STMicroelectronics LF18CPT-TR

Overview

LF18CPT-TR from STMicroelectronics is a 1.8 V, ±2% tolerance, automotive-grade low-dropout linear regulator in PPAK-5 package with logic-controlled shutdown, 500 mA output current capability, 0.7 V dropout at 200 mA, and operation from −40 °C to 125 °C - used for local power regulation in engine control units and ADAS domain controllers.

For engineers reviewing the LF18CPT-TR datasheet, LF18CPT-TR pinout, LF18CPT-TR application, or LF18CPT-TR equivalent, this page delivers verified electrical specs, thermal performance data, automotive qualification status (AEC-Q100), and real-world use context for battery-backed subsystems requiring ultra-low quiescent current (50 µA OFF mode) and stable low-noise 1.8 V supply.

Technical Context

The LF18CPT-TR implements a PNP-based LDO architecture with internal current and thermal limiting, enabling robust operation under transient load and overtemperature conditions without external protection circuitry. Its TTL-compatible inhibit input (Pin 2) allows precise system-level power sequencing and standby control.

Stability is achieved with only 2.2 µF output capacitance (ESR 0.1–10 Ω), reducing BOM count and PCB area versus legacy regulators. The device maintains 82 dB PSRR at 120 Hz and 50 µV RMS output noise (10 Hz–100 kHz), making it suitable for noise-sensitive analog and digital loads.

Key Specifications

Pinout & Package

LF18CPT-TR uses the PPAK-5 surface-mount package (SOT-223-5 variant), featuring an exposed thermal pad electrically tied to GND for improved heat dissipation (R_thJA = 100 °C/W, R_thJC = 8 °C/W). The 5-pin configuration supports logic-controlled shutdown.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLV73318PDBVR and NCP1117ST18T3G, LF18CPT-TR uniquely combines AEC-Q100 Grade 1 qualification, 5-pin PPAK thermal performance, and TTL inhibit functionality - making it the sole choice for automotive LDO applications demanding both reliability and active power management.

Availability

LF18CPT-TR is available at Aetrix Electronics and suitable for engine control units, ADAS camera modules, body control modules, and infotainment head units requiring stable component supply across automotive production lifecycles.

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

LF18CPT-TR belongs to the LFXX family of automotive-grade LDOs engineered specifically for harsh-environment power management in engine, chassis, and safety-critical electronic control units.

FAQ

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

The LF18CPT-TR requires VI ≥ VO + V_d = 1.8 V + 1.3 V = 3.1 V to maintain regulation at 500 mA (per Table 6, max dropout is 1.3 V). Below 3.1 V, output voltage drops linearly with input; the device remains functional but exits regulation.

Can the INH pin be left floating in the application?

No - the INH pin must be actively driven to either logic high (>2 V) or logic low (<0.8 V). Floating INH causes undefined regulator state and potential oscillation due to internal input hysteresis; tie to GND or V_IN via resistor if not controlled by a microcontroller.

Is the exposed thermal pad on the PPAK-5 package required to be soldered to PCB ground?

Yes - the TAB (Pin 5) is electrically connected to GND and serves as the primary thermal conduction path. Omitting solder connection to a ≥1 cm² copper pour degrades R_thJA by >40 °C/W and risks thermal shutdown under 300+ mA load.

Does LF18CPT-TR support ceramic output capacitors with ESR below 0.1 Ω?

No - the datasheet specifies CO stability range for ESR = 0.1–10 Ω. Capacitors with ESR <0.1 Ω (e.g., some X7R/X5R MLCCs) may cause phase margin loss and oscillation; use CO with ≥0.1 Ω ESR or add a 0.1 Ω series resistor if low-ESR ceramics are mandated.