STMicroelectronics L79L05ACD13TR

Overview

L79L05ACD13TR 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 and is designed for local on-card regulation in noise-sensitive analog and mixed-signal circuits such as sensor signal conditioning and low-power microcontroller power rails.

For engineers reviewing the L79L05ACD13TR datasheet, L79L05ACD13TR pinout, L79L05ACD13TR application, or L79L05ACD13TR equivalent, key selection criteria include guaranteed ±5% output tolerance at -5 V, 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 (with 6 cm² PCB copper heat-sink).

Technical Context

The L79L05ACD13TR implements a monolithic PNP pass transistor architecture with built-in thermal overload and short-circuit protection circuitry, enabling robust operation without external safety components. Its internal current limit prevents destructive overloads, while the thermal shutdown activates at junction temperatures exceeding 125 °C.

Designed for fixed-output negative regulation, it operates with input voltages down to -7 V and up to -20 V (for -5 V output), maintaining regulation across load currents from 1 mA to 100 mA and ambient temperatures from 0 °C to 125 °C. The device achieves stable performance with only 0.33 µF input and 0.1 µF output ceramic capacitors.

Key Specifications

Pinout & Package

Supplied in TO-92 package (ECOPACK® compliant), with 3 leads: Input (pin 1), Ground (pin 2), Output (pin 3). Package dimensions: 4.32–4.95 mm height, 4.45–4.95 mm width, 3.30–3.94 mm depth; lead pitch 2.54 mm.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM79L05ACZ and MC79L05ACPG, the L79L05ACD13TR offers superior noise performance (40 µV vs 100 µV), better supply rejection (49 dB vs 35 dB), and certified environmental compliance (ECOPACK®), making it optimal for new designs demanding precision, reliability, and regulatory alignment.

Availability

L79L05ACD13TR is available at Aetrix Electronics and suitable for industrial sensor interfaces, low-power microcontroller subsystems, RS-232 communication modules, and audio preamp bias supplies requiring stable component supply and long-term manufacturability.

Supply support for L79L05ACD13TR 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 negative voltage regulation in space-constrained and thermally challenging PCB environments.

FAQ

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

The L79L05ACD13TR 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. At lighter loads (e.g., 40 mA), regulation holds down to -6.5 V input. Operation below -6.7 V results in unregulated output voltage collapse.

Can this regulator be used in parallel to increase output current?

No - the L79L05ACD13TR is not designed for parallel operation. Its output voltage tolerance (±5%) and lack of current-sharing control circuitry make paralleling unstable and prone to thermal runaway. For >100 mA, use a single higher-current regulator like the L79M05 or add an external pass transistor.

Is a heatsink required for continuous 100 mA operation?

A dedicated metal heatsink is not required, but PCB copper area is essential: ≥6 cm² of 2-oz copper connected to pin 2 (ground) reduces R_thJA from 200 °C/W to ~100 °C/W, enabling safe 100 mA operation at 70 °C ambient. Without copper heat-sinking, continuous 100 mA exceeds thermal limits above 45 °C ambient.

Does this part support reverse-polarity input protection?

No - the L79L05ACD13TR has no built-in reverse-polarity protection. Applying positive voltage to pin 1 (input) or reversing input polarity will cause immediate device failure. External protection (e.g., series diode or MOSFET-based reverse-voltage guard) must be added if input polarity risk exists in the system.