STMicroelectronics L7915CT

Overview

L7915CT from STMicroelectronics is a three-terminal fixed negative voltage regulator delivering -15 V output at up to 1.5 A, featuring thermal overload protection, short-circuit protection, and SOA-controlled output transition. It operates with input voltages down to -35 V (for VO = -15 V), supports local on-card regulation in split-supply systems, and is commonly used in ±15 V analog power rails for op-amp circuits and industrial control interfaces.

For engineers reviewing the L7915CT datasheet, L7915CT pinout, L7915CT application, or L7915CT equivalent, key selection criteria include guaranteed -15 V output tolerance (±4%), dropout voltage of 1.1 V at 1 A, junction temperature range of 0–150 °C, and compatibility with TO-220FP package heat sinking for sustained 1.5 A operation.

Technical Context

The L7915CT implements a monolithic PNP pass transistor architecture with internal current limiting, thermal shutdown, and safe operating area (SOA) protection-ensuring robustness during transient overloads and input-to-output reversals. Its feedback loop maintains output regulation across line variations (-18.5 V to -30 V input) and load currents from -5 mA to -1.5 A.

Designed as a complementary counterpart to the L78xx positive regulator series, it enables symmetrical dual-rail supplies without external compensation. The device requires only two external capacitors (2.2 µF input, 1 µF output) for stability, with optional input-to-output diode protection recommended for systems prone to momentary input shorts.

Key Specifications

Pinout & Package

Supplied in TO-220FP package: thermally enhanced plastic housing with insulated tab, 3-pin vertical mounting footprint, and integrated heatsink interface via metal tab (pin 2). Compatible with standard TO-220 heatsinks using insulating washers.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM337T and MC7915BT, the L7915CT offers superior thermal robustness (SOA + 150 °C shutdown), higher output current headroom (1.5 A), and better ripple suppression (60 dB), making it optimal for industrial analog systems demanding reliability over adjustability or ultra-low-cost sourcing.

Availability

L7915CT is available at Aetrix Electronics and suitable for industrial analog signal conditioning, split-rail op-amp power supplies, and legacy control interface replacements requiring stable component supply and long-term manufacturability.

Supply support for L7915CT 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 MEMS sensors for industrial, automotive, and consumer markets.

The L79xxC series was developed specifically for cost-effective, robust local regulation in industrial power supplies and analog systems-emphasizing fault resilience, thermal safety, and compatibility with legacy TO-220 infrastructure.

FAQ

What is the maximum input voltage for L7915CT?

The absolute maximum DC input voltage is -35 V when regulating -15 V output. Operation above this risks permanent damage. For reliable long-term use, ST recommends keeping input within -18.5 V to -30 V per electrical characteristics testing conditions, ensuring adequate headroom for ripple and transient spikes.

Can L7915CT be used without a heatsink?

Yes, but only at very low output currents (<200 mA) and ambient temperatures <40 °C. At 1.5 A, junction temperature rise exceeds 100 °C without heatsinking due to RthJA = 60 °C/W (TO-220FP). A minimum 10 cm² aluminum heatsink is required for full-load operation at 70 °C ambient.

Is an input capacitor mandatory for L7915CT stability?

Yes - a minimum 2.2 µF solid tantalum capacitor is required at the input if the regulator is located more than 2 inches from the main power supply filter. This prevents oscillation and improves transient response. Aluminum electrolytic capacitors may be used only if ≥22 µF and placed close to the input pin.

Does L7915CT support adjustable output voltage configurations?

Yes - though designed as a fixed -15 V regulator, it can be configured for adjustable output using external resistors per Figure 6 in the datasheet. However, doing so voids guaranteed specifications (e.g., line/load regulation, dropout), and the internal feedback network must remain unaltered to retain thermal protection functionality.