STMicroelectronics L79L08ACD

Overview

L79L08ACD from STMicroelectronics is a three-terminal fixed negative voltage regulator delivering -8 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 -10.5 V to -23 V input, with ±4% output voltage tolerance at 25°C and 1.7 V dropout voltage - ideal for local on-card regulation in industrial control and embedded power subsystems.

For engineers reviewing the L79L08ACD datasheet, L79L08ACD pinout, L79L08ACD application, or L79L08ACD equivalent, this device serves as a drop-in replacement for Zener/resistor regulators in low-noise, space-constrained negative rail generation where quiescent current (6 mA typ.), load regulation (±40 mV), and supply rejection (37–45 dB) are critical selection criteria.

Technical Context

The L79L08ACD implements a monolithic bipolar linear regulator architecture with built-in thermal shutdown and foldback current limiting. Its internal circuitry maintains stable -8 V output across input voltages from -10.5 V to -23 V and load currents from 1 mA to 100 mA, while exhibiting 60 µV RMS output noise (10 Hz–100 kHz) and 37–45 dB supply voltage rejection at 120 Hz.

It operates over an extended junction temperature range of 0°C to +125°C and supports SO-8, TO-92, and SOT-89 packages - with SO-8 variant (L79L08ACD) using internally connected pins 2, 3, 6, and 7 to the die attach flag for enhanced thermal performance (R_thj-case = 20°C/W).

Key Specifications

Pinout & Package

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

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM7908CD and MC79L08ACDR2G, the L79L08ACD offers superior thermal performance in SO-8 via its integrated flag connection, lower noise than the ON Semiconductor part, and tighter tolerance than the TI part - making it optimal for industrial embedded systems demanding reliability under sustained load and ambient temperature variation.

Availability

L79L08ACD is available at Aetrix Electronics and suitable for industrial sensor interfaces, RS-232 transceiver biasing, and embedded microcontroller peripheral power requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for L79L08ACD 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 power management applications.

The L79L00 series belongs to ST's legacy linear regulator product line, engineered specifically for robust, low-cost, fixed-voltage negative rail generation in space-constrained and thermally demanding industrial environments.

FAQ

What is the minimum input voltage required for stable -8 V output at 100 mA?

The L79L08ACD requires a minimum input voltage of -9.7 V (i.e., |VI| ≥ 9.7 V) to maintain regulation at full 100 mA load, based on its 1.7 V dropout specification. Operation below this threshold results in unregulated output proportional to input voltage minus dropout loss.

Can L79L08ACD be used in parallel to increase output current?

No - the L79L08ACD lacks built-in current-sharing circuitry or matching output impedance for parallel operation. Attempting parallel connection risks thermal runaway and uneven current distribution; use a single higher-current regulator or external pass transistor instead.

Is the SO-8 package of L79L08ACD compatible with standard SO-8 footprints?

Yes, the external dimensions match standard SO-8, but pins 2, 3, 6, and 7 are internally connected to the die attach flag. PCB layout must expose these pins to a common thermal pad or large copper pour to realize the specified 55°C/W R_thj-amb - standard SO-8 land patterns require minor modification for optimal thermal performance.

Does L79L08ACD require input and output capacitors, and what values are recommended?

Yes - STMicroelectronics specifies a minimum 0.33 µF ceramic or tantalum input capacitor and 0.1 µF output capacitor for stability and transient response. Larger values (e.g., 1 µF input, 10 µF output) improve ripple rejection and load step recovery but are not mandatory for basic functionality.