STMicroelectronics L79L05ABUTR

Overview

L79L05ABUTR from STMicroelectronics is a three-terminal fixed negative voltage regulator delivering -5 V output at up to 100 mA, featuring internal current limiting, thermal shutdown, and short-circuit protection. It requires no external components, operates over -40 °C to +125 °C junction temperature, and achieves 41–49 dB supply voltage rejection at 120 Hz - used for local on-card regulation in industrial control power rails and analog sensor biasing.

For engineers reviewing the L79L05ABUTR datasheet, L79L05ABUTR pinout, L79L05ABUTR application, or L79L05ABUTR equivalent, key selection criteria include guaranteed -5 V output tolerance (±5%), dropout voltage of 1.7 V, low 40 µV RMS output noise (10 Hz–100 kHz), and TO-92 package thermal resistance (R_thJA = 200 °C/W).

Technical Context

The L79L05ABUTR implements a monolithic PNP pass transistor architecture with built-in thermal overload and short-circuit protection circuitry. Its regulation loop maintains stable -5 V output across input voltages from -7 V to -20 V and load currents from 1 mA to 100 mA.

It replaces Zener diode/resistor networks with two orders-of-magnitude lower output impedance, reduced quiescent current (6 mA typical at 25 °C), and improved line/load regulation (≤100 mV and ≤30 mV respectively under specified conditions).

Key Specifications

Pinout & Package

Supplied in TO-92 package (ECOPACK® compliant), with 3 leads: Input (pin 1), Ground (pin 2), Output (pin 3). Pin 2 is internally connected to the metal tab for thermal conduction.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM79L05ACZ and MC79L05ACPR, the L79L05ABUTR provides wider temperature coverage, lower noise, and tighter SVR - making it optimal for industrial-grade analog signal chains where reliability and spectral purity are critical.

Availability

L79L05ABUTR is available at Aetrix Electronics and suitable for industrial sensor nodes, RS-232 interface modules, and analog audio subsystems requiring stable component supply with full production lifecycle support.

Supply support for L79L05ABUTR 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.

The L79L series belongs to ST's legacy linear regulator product line, engineered specifically for cost-effective, robust local regulation in space-constrained PCBs where simplicity and reliability outweigh switching efficiency requirements.

FAQ

What is the minimum input voltage required for regulation?

The L79L05ABUTR requires a minimum input-to-output differential of 1.7 V to maintain regulation. With a nominal -5 V output, the absolute minimum input voltage is -6.7 V. Operation below this threshold results in unregulated output that tracks the input minus dropout.

Can this regulator be used in parallel for higher current?

No - the L79L05ABUTR lacks current-sharing capability and has no provision for master-slave synchronization. Parallel connection risks thermal runaway due to mismatched output voltages and is not supported by ST. Use a single higher-current regulator or external pass transistor instead.

Is an input capacitor mandatory?

While the datasheet states "no external components required," ST recommends a 0.33 µF ceramic input capacitor placed within 1 cm of the input pin to suppress high-frequency noise and prevent oscillation under dynamic load conditions - especially when sourced from long traces or switch-mode supplies.

Does the TO-92 package require a heatsink for 100 mA operation?

At 100 mA and ambient temperature of 25 °C, the TO-92 package dissipates ~170 mW (|VI – VO| × IO ≈ 1.7 V × 100 mA). With R_thJA = 200 °C/W, junction temperature rise is ~34 °C - well within the -40 °C to +125 °C rating. No heatsink is needed for this condition, but PCB copper area improves margin.