STMicroelectronics L79L05ACZ-TR

Overview

L79L05ACZ-TR 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 -40 °C to 125 °C junction temperature, with ±5% output voltage tolerance (AC grade), commonly used in local on-card regulation for noise-sensitive analog subsystems in industrial control and embedded power rails.

For engineers reviewing the L79L05ACZ-TR datasheet, L79L05ACZ-TR pinout, L79L05ACZ-TR application, or L79L05ACZ-TR 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), load regulation (±30 mV over 1–40 mA), and TO-92 package thermal resistance (R_thJA = 200 °C/W).

Technical Context

The L79L05ACZ-TR implements a monolithic PNP-based linear regulation architecture with built-in thermal shutdown and foldback current limiting. Its internal design eliminates need for external compensation or bypass capacitors beyond minimum input (0.33 µF) and output (0.1 µF) ceramics.

It operates as a fixed-output negative regulator with a guaranteed dropout voltage of 1.7 V across full load (1–100 mA) and temperature range (-40 to 125 °C), maintaining output stability under line variations from -7 V to -20 V input and load steps up to 100 mA.

Key Specifications

Pinout & Package

Supplied in TO-92 package (ECOPACK® compliant), with 3 leads: Input (pin 1), Ground (pin 2), Output (pin 3). The TO-92 outline conforms to ST's mechanical data (DocID2511 Rev 18, Section 5.1), with typical dimensions: D = 4.45–4.95 mm, E = 3.30–3.94 mm, L = 12.70–15.49 mm.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM79L05ACZ and MC79L05ACPRAG, the L79L05ACZ-TR offers superior noise performance (40 µV vs. 65 µV) and supply rejection (49 dB vs. 38 dB), making it preferred for precision analog applications, while its TO-92 package provides lowest cost and widest availability for standard through-hole assembly.

Availability

L79L05ACZ-TR is available at Aetrix Electronics and suitable for industrial sensor signal conditioning, legacy RS-232 transceiver bias, and embedded microcontroller analog peripherals requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for L79L05ACZ-TR 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 was developed as a drop-in replacement for discrete Zener/resistor regulators, targeting cost-sensitive, space-constrained applications needing reliable fixed negative voltage regulation without external components.

FAQ

What is the minimum input voltage required for stable -5 V output at 100 mA?

The L79L05ACZ-TR requires a minimum input voltage of -6.7 V to maintain regulation at full 100 mA load, based on its 1.7 V dropout specification. Below this, output voltage collapses linearly with input; operation below -6.7 V is not guaranteed per datasheet electrical characteristics.

Can L79L05ACZ-TR replace a Zener diode/resistor network in existing designs?

Yes - it directly replaces -5 V Zener/resistor combinations with identical pinout (cathode to input, anode to ground, output taken from cathode), offering two orders of magnitude lower output impedance, 50% lower quiescent current, and integrated thermal/short-circuit protection without redesigning the PCB layout.

Is a heat sink required for continuous 100 mA operation at 70 °C ambient?

No external heat sink is required for 100 mA at 70 °C ambient when using the TO-92 package, as thermal calculations show junction temperature remains below 125 °C (T_J ≈ 112 °C) assuming 200 °C/W R_thJA and 1.7 V dropout dissipation (170 mW). Board-level copper pour further improves margin.

Does L79L05ACZ-TR require input and output capacitors, and what values are recommended?

Yes - ST specifies minimum 0.33 µF ceramic at input and 0.1 µF ceramic at output for stability and transient response. Larger values (e.g., 10 µF tantalum at output) improve load step recovery but are not mandatory; electrolytics are discouraged due to ESR-related instability risks.