STMicroelectronics L7918CV

Overview

L7918CV from STMicroelectronics is a three-terminal fixed negative voltage regulator delivering -18 V output at up to 1.5 A, featuring thermal overload protection, short-circuit protection, and SOA-limited output transition. It operates with input voltages up to -40 V (for VO = -20 to -24 V), supports local on-card regulation, and is optimized for split-supply systems alongside L78xx positive regulators.

For engineers reviewing the L7918CV datasheet, L7918CV pinout, L7918CV application, or L7918CV equivalent, key selection criteria include guaranteed -18 V output tolerance (±5%), dropout voltage of 1.1 V at 1 A, junction temperature range of 0–150 °C, and TO-220FP package compatibility with standard heat sinking for sustained 1.5 A delivery.

Technical Context

The L7918CV implements a monolithic PNP pass transistor-based linear regulation architecture with internal current limiting, thermal shutdown, and safe operating area (SOA) protection. Its feedback loop maintains stable output under load transients and line variations, with supply voltage rejection of 54–60 dB at 120 Hz.

Designed for fixed-output operation, it requires no external components for basic functionality but supports adjustable configurations via external resistors. Input-to-output differential must remain ≥1.1 V to sustain regulation, and stability mandates ≥2.2 µF solid tantalum input capacitor when located remotely from bulk filtering.

Key Specifications

Pinout & Package

Supplied in TO-220FP package: thermally enhanced variant of TO-220 with dual-gauge leadframe, 5 °C/W junction-to-case thermal resistance, and standardized mounting hole for mechanical attachment and heatsink interface.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar negative fixed-voltage regulation applications.

Compared with LM337T and MC7918CT, the L7918CV offers superior thermal performance in TO-220FP packaging, lower quiescent current for battery-backed systems, and guaranteed SOA protection-making it optimal for high-reliability industrial analog rails where fixed -18 V and robust fault handling are mandatory.

Availability

L7918CV is available at Aetrix Electronics and suitable for industrial PLC I/O modules, audio preamp power rails, bipolar op-amp biasing, and test & measurement instrumentation requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for L7918CV 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 microcontrollers, power management ICs, analog chips, and discrete devices for industrial, automotive, and consumer markets.

The L79xxC series was developed specifically for cost-sensitive, high-reliability linear regulation in dual-rail analog systems-emphasizing thermal robustness, fault resilience, and direct compatibility with the L78xx positive regulator family.

FAQ

What is the minimum input voltage required for L7918CV to maintain regulation?

The minimum input voltage is -19.1 V DC, calculated as VO + V_d = -18 V + 1.1 V dropout. Below this, output voltage collapses nonlinearly. Input must also stay within absolute maximum rating of -40 V for -18 V output variants per Table 2.

Can L7918CV be used in adjustable configurations?

Yes-though designed as a fixed -18 V regulator, it can be configured for adjustable output using external resistors per Figure 6 in the datasheet. The ADJ pin is not exposed; adjustment is achieved by elevating the ground terminal potential with a resistor divider referenced to output.

Is a heat sink mandatory for 1.5 A continuous operation?

Yes. With R_thJC = 5 °C/W and R_thCA ≈ 55 °C/W (typical TO-220FP on 1-in² copper), power dissipation at 1.5 A and 1.1 V dropout is ~1.65 W-raising junction temperature ~90 °C above ambient. A heatsink is required to keep T_J ≤ 150 °C at 70 °C ambient.

What capacitor types and values are mandatory for stable operation?

A minimum 2.2 µF solid tantalum capacitor is required at the input (C_I) if the regulator is >2 inches from bulk filter; aluminum electrolytic may be used only at ≥22 µF. Output requires ≥1 µF solid tantalum (C_O)-aluminum types need ≥10 µF and risk instability if ESR is too low.