STMicroelectronics L79L12ACZ-AP

Overview

L79L12ACZ-AP from STMicroelectronics is a three-terminal fixed negative linear voltage regulator delivering -12 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 designed for local on-card regulation in industrial control, instrumentation, and embedded power subsystems where noise rejection and stable low-current biasing are critical.

For engineers reviewing the L79L12ACZ-AP datasheet, L79L12ACZ-AP pinout, L79L12ACZ-AP application, or L79L12ACZ-AP equivalent, this device serves as a drop-in replacement for Zener/resistor networks in low-noise, low-quiescent-current negative supply rails - with confirmed 80 µV RMS output noise, ±5% output tolerance, and 1.7 V dropout voltage at 40 mA.

Technical Context

The L79L12ACZ-AP implements a monolithic bipolar linear regulator architecture with built-in thermal shutdown and foldback current limiting. Its internal structure eliminates need for external compensation, enabling stable operation with only 0.33 µF input and 0.1 µF output capacitors.

It operates across an input voltage range of -14.5 V to -27 V for nominal -12 V output, maintaining regulation over load currents from 1 mA to 100 mA and junction temperatures from 0 °C to 125 °C. Supply voltage rejection reaches 42 dB at 120 Hz under standard test conditions.

Key Specifications

Pinout & Package

Package: TO-92 - compact through-hole plastic package with 3 leads, optimized for low-cost board-level power regulation and manual assembly.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar negative fixed-voltage regulation applications.

Compared with LM7912CD and MC79L12ACPRPG, the L79L12ACZ-AP offers identical regulation performance in a legacy-compatible TO-92 through-hole package - making it optimal for cost-sensitive, manually assembled, or retrofit applications where board real estate and thermal load are moderate.

Availability

L79L12ACZ-AP is available at Aetrix Electronics and suitable for industrial sensor biasing, op-amp dual-rail generation, and embedded peripheral powering requiring stable component supply, long-lifecycle support, and consistent parametric performance across production batches.

Supply support for L79L12ACZ-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 analog, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The L79L00 series belongs to ST's legacy linear regulator product line, engineered specifically for cost-effective, robust local regulation in space- and power-constrained embedded systems - emphasizing simplicity, reliability, and compatibility with legacy designs.

FAQ

What is the maximum input voltage for L79L12ACZ-AP?

The absolute maximum DC input voltage is -35 V when configured for -12 V output. For reliable operation within specifications, ST recommends keeping input between -14.5 V and -27 V. Exceeding -35 V risks permanent damage due to internal junction breakdown, even with thermal protection active.

Can L79L12ACZ-AP be used in parallel for higher current?

No - the L79L12ACZ-AP lacks current-sharing capability and has no built-in balancing features. Parallel connection causes unequal current distribution due to output voltage tolerances (±5%), leading to thermal runaway in the unit with lowest VOUT. Use a single higher-current regulator or external pass transistor instead.

Is a heat sink required for continuous 100 mA operation?

At 100 mA with 15 V input-to-output differential (-27 V IN → -12 V OUT), power dissipation reaches 1.5 W. The TO-92 package has R_thj-amb ≈ 200 °C/W, resulting in ~300 °C junction rise - far exceeding 125 °C limit. A minimum 2 cm² copper pour is mandatory; full heatsinking is recommended for sustained 100 mA use.

Does L79L12ACZ-AP require input and output capacitors?

Yes - ST specifies 0.33 µF tantalum or aluminum electrolytic at VIN and 0.1 µF ceramic at VOUT for stability. Omitting either capacitor risks oscillation, especially under light or dynamic loads. The 0.1 µF output cap must be placed within 5 mm of pins 2 and 3 to minimize parasitic inductance.