STMicroelectronics L79L05ACD

Overview

L79L05ACD from STMicroelectronics is a three-terminal fixed negative voltage regulator delivering -5 V output at up to 100 mA, featuring internal current limiting, thermal overload protection, and short-circuit protection. It requires no external components and is specified for operation from -7 V to -20 V input across 0°C to 125°C junction temperature, commonly used in local on-card regulation for noise-sensitive analog subsystems.

For engineers reviewing the L79L05ACD datasheet, L79L05ACD pinout, L79L05ACD application, or L79L05ACD equivalent, this device serves as a drop-in replacement for Zener diode/resistor regulators in low-noise, low-power negative rail generation where output impedance, quiescent current, and supply rejection are critical selection criteria.

Technical Context

The L79L05ACD implements a monolithic bipolar linear regulator architecture with built-in thermal shutdown and foldback current limiting. Its output voltage is trimmed during manufacturing to ±2% tolerance (AC grade) at 25°C and maintains ±5% over full load (1–100 mA) and line (VI = -7 to -20 V) conditions.

It achieves 41–49 dB supply voltage rejection at 120 Hz with 40 µV RMS output noise (10 Hz–100 kHz), and sustains regulation with a 1.7 V dropout voltage-enabling stable -5 V rail generation from inputs as low as -6.7 V under worst-case load and temperature.

Key Specifications

Pinout & Package

Package: SO-8 (modified internal frame with pins 2, 3, 6, and 7 electrically connected to die attach flag for enhanced thermal performance; R_thj-amb = 55°C/W with 6 cm² PCB copper heatsink).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM79L05AC and MC79L05ACDR2G, the L79L05ACD delivers superior thermal performance via its internally bonded flag, lower output noise for analog signal integrity, and tighter initial tolerance-making it optimal for new designs prioritizing precision, reliability, and space-constrained thermal management.

Availability

L79L05ACD is available at Aetrix Electronics and suitable for industrial sensor conditioning, RS-232 interface design, and medical analog front-end power supply requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for L79L05ACD 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 analog, power, MCU, and sensor solutions for industrial, automotive, and consumer markets.

The L79L00 series belongs to ST's legacy linear regulator product line, engineered specifically for robust, low-cost, no-compromise negative voltage regulation in space- and reliability-constrained embedded systems.

FAQ

What is the minimum input voltage required for L79L05ACD to maintain regulation?

The L79L05ACD requires a minimum input voltage of -6.7 V to sustain -5 V output under worst-case conditions (100 mA load, 125°C junction temperature), based on its 1.7 V dropout specification. At 25°C and 40 mA load, regulation holds down to -6.5 V. Input below -6.7 V causes output collapse and unregulated behavior.

Can L79L05ACD replace a Zener diode/resistor network in existing designs?

Yes-L79L05ACD directly replaces discrete -5 V Zener/resistor regulators with identical pinout (TO-92/SOT-89 variants) and offers two orders-of-magnitude lower output impedance, 6 mA vs. 15–20 mA quiescent current, and 40 µV vs. >200 µV noise. No layout changes needed beyond adding 0.33 µF input and 0.1 µF output capacitors.

Does L79L05ACD require external capacitors, and what values are recommended?

Yes: a 0.33 µF ceramic capacitor between VIN and GND, and a 0.1 µF ceramic capacitor between VOUT and GND are mandatory for stability and transient response per ST's test circuits. Larger values (e.g., 10 µF tantalum) may be added in parallel for improved low-frequency ripple suppression but are not required for basic operation.

How does the SO-8 package's internal flag connection improve thermal performance?

The SO-8 variant ties pins 2, 3, 6, and 7 to the die attach flag, effectively increasing copper surface area for heat conduction. With 6 cm² PCB copper heatsink, R_thj-amb drops to 55°C/W-45% lower than standard SO-8-enabling 100 mA continuous operation at ambient temperatures up to 85°C without external heatsinks.