STMicroelectronics L79L05ABZ-AP

Overview

L79L05ABZ-AP from STMicroelectronics is a three-terminal negative linear voltage regulator delivering a fixed -5 V output at up to 100 mA, featuring internal current limiting, thermal shutdown, and short-circuit protection. It requires no external components and is specified for operation across -40 °C to +125 °C junction temperature, making it suitable for on-card local regulation in industrial control and embedded power subsystems.

For engineers reviewing the L79L05ABZ-AP datasheet, L79L05ABZ-AP pinout, L79L05ABZ-AP application, or L79L05ABZ-AP equivalent, key selection criteria include its ±5% output voltage tolerance (AB grade), 1.7 V dropout voltage, 40 µV RMS output noise (10 Hz–100 kHz), 41–49 dB supply voltage rejection, and TO-92 package thermal resistance of 200 °C/W (ambient).

Technical Context

The L79L05ABZ-AP implements a monolithic PNP pass transistor architecture with built-in thermal overload and short-circuit protection circuitry. Its internal current limiting ensures safe operation under fault conditions without external sensing components.

It operates as a fixed-output negative regulator with a minimum input voltage of -7 V and maximum of -20 V for stable -5 V regulation across load currents from 1 mA to 100 mA. The device achieves 30 mV load regulation (1–40 mA) and 100 mV line regulation (VI = -8 to -20 V) at 25 °C.

Key Specifications

Pinout & Package

Package: TO-92 (plastic, 3-pin, through-hole). Pin identification is standardized per ST's top-view orientation: Pin 1 = Input (IN), Pin 2 = Ground (GND), Pin 3 = Output (OUT).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM7905ACZ and MC79L05ACPR, the L79L05ABZ-AP provides superior low-temperature operation, lower noise, and higher PSRR-critical for analog signal chains-while maintaining identical TO-92 footprint and pinout compatibility.

Availability

L79L05ABZ-AP is available at Aetrix Electronics and suitable for industrial sensor nodes, legacy serial interface designs, and automotive ECU peripheral power requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for L79L05ABZ-AP 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 microcontrollers, power management ICs, sensors, and analog components for industrial, automotive, and consumer markets.

The L79L series belongs to ST's legacy linear regulator product line, engineered specifically for robust, low-cost, fixed-voltage negative regulation in space-constrained and thermally demanding embedded systems.

FAQ

What is the minimum input voltage required for regulation with L79L05ABZ-AP?

The L79L05ABZ-AP requires a minimum input voltage of −7 V to maintain −5 V output regulation at full 100 mA load. This is determined by its 1.7 V dropout voltage specification: |VI| ≥ |VO| + V_DROP = 5 V + 1.7 V = 6.7 V → rounded to −7 V absolute value. Operation below this threshold results in unregulated output.

Can L79L05ABZ-AP be used in parallel to increase output current?

No-L79L05ABZ-AP is not designed for parallel operation. Its output voltage tolerance (±5%) and lack of current-sharing features (e.g., remote sense, current-balancing resistors) would cause unequal load distribution and potential thermal runaway. For >100 mA, use a higher-current regulator like L79M05 or add an external pass transistor.

Is a heat sink required for continuous 100 mA operation?

Yes-under worst-case conditions (T_A = 85 °C, no PCB copper heatsink), the TO-92 package's 200 °C/W R_thJA yields a junction temperature rise of 200 × 0.1 A × 1.7 V ≈ 34 °C, reaching ~119 °C. To stay within the 125 °C max junction limit, ≥6 cm² of 1-oz copper pour is recommended as a minimum heatsink area.

What output capacitor is required for stability?

A minimum 0.1 µF ceramic capacitor is required at the output (pin 3) for stability, per ST's test circuit and electrical characteristics table. Input capacitance of 0.33 µF is also recommended. Larger values (e.g., 1–10 µF tantalum) improve transient response but are not mandatory for basic regulation.