STMicroelectronics L79L05ACUTR

Overview

L79L05ACUTR from STMicroelectronics is a three-terminal fixed negative linear 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 with input voltages down to -30 V (for -5 V output), and maintains ±5% output tolerance across 0–125 °C junction temperature. It is used for local on-card regulation in industrial control power supplies to suppress noise and mitigate distribution losses.

For engineers reviewing the L79L05ACUTR datasheet, L79L05ACUTR pinout, L79L05ACUTR application, or L79L05ACUTR equivalent, key selection criteria include dropout voltage (1.7 V), output noise (40 µV RMS, 10 Hz–100 kHz), supply voltage rejection (41–49 dB at 120 Hz), and thermal resistance (200 °C/W in TO-92) - all critical for low-noise analog subsystems and embedded microcontroller bias rails.

Technical Context

The L79L05ACUTR implements a monolithic PNP-based series pass architecture with integrated bandgap reference, error amplifier, and protection circuitry. Its fixed -5 V output is trimmed during wafer test to ±5% accuracy at 25 °C and maintained over load (1–100 mA) and line (VI = -7 to -20 V) variations.

Thermal overload protection activates at ~150 °C junction temperature, and short-circuit current is internally limited to ~150 mA. The device achieves 40 µV RMS output noise due to internal filtering and low quiescent current (6 mA typical at 25 °C), enabling stable biasing of op-amps and ADC references without external capacitors beyond minimum 0.33 µF input and 0.1 µF output.

Key Specifications

Pinout & Package

Package: TO-92 (3-lead plastic transistor outline), lead material: matte tin, RoHS-compliant ECOPACK® grade.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM79L05ACZ and MC79L05ACP, the L79L05ACUTR delivers superior noise performance (40 µV vs ≥65 µV), tighter line regulation (100 mV vs 150 mV), and better thermal efficiency (200 vs ≥220 °C/W), making it optimal for noise-sensitive analog subsystems requiring long-term stability.

Availability

L79L05ACUTR is available at Aetrix Electronics and suitable for industrial sensor signal conditioning, RS-232 transceiver bias, and microcontroller analog peripheral power requiring stable component supply across extended temperature ranges and multi-year production cycles.

Supply support for L79L05ACUTR 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 since 1987.

The L79L series belongs to ST's legacy linear regulator product line, engineered specifically for cost-effective, robust local regulation in space-constrained industrial and embedded systems where reliability and minimal external components are critical.

FAQ

What is the minimum input voltage required for regulation with L79L05ACUTR?

The absolute minimum input voltage is -6.7 V, calculated as VO + V_dropout = -5 V + 1.7 V. Operation below this causes loss of regulation and rising output impedance. For reliable performance across temperature and load, ST recommends VI ≥ -7 V, with derating above 100 mA or ambient >75 °C due to thermal limits in TO-92 packaging.

Can L79L05ACUTR replace a Zener diode and resistor network?

Yes - it replaces -5 V Zener/resistor combinations with significantly improved performance: output impedance is ~100× lower, quiescent current is ~3× lower (6 mA vs ~18 mA), and output noise is ~5× lower (40 µV vs ~200 µV). No external components are needed beyond the mandatory 0.33 µF input and 0.1 µF output ceramic capacitors.

Is heat sinking required for 100 mA operation?

In TO-92 packaging, heat sinking is not required for short bursts, but continuous 100 mA operation at ambient >55 °C risks thermal shutdown. With 200 °C/W R_thJA, 100 mA × 1.7 V dropout = 170 mW dissipation → 34 °C rise. At 75 °C ambient, junction reaches 109 °C - within 0–125 °C rating. A 1 cm² copper pour reduces R_thJA to ~120 °C/W, adding safety margin.

Does L79L05ACUTR support reverse-polarity input protection?

No - the device lacks internal reverse-polarity protection. Applying positive voltage to Pin 3 (collector/input) or reversing input polarity will cause catastrophic failure. External protection (e.g., series Schottky diode or PMOS FET) is required in environments prone to wiring errors or battery reversal.