STMicroelectronics L79L08ACZ

Overview

L79L08ACZ from STMicroelectronics is a three-terminal fixed negative voltage regulator delivering -8 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 -10.5 V to -23 V input across 0 °C to +125 °C junction temperature, commonly used in local on-card regulation for noise-sensitive analog subsystems.

For engineers reviewing the L79L08ACZ datasheet, L79L08ACZ pinout, L79L08ACZ application, or L79L08ACZ equivalent, this device serves as a drop-in replacement for Zener-diode/resistor regulators in low-noise, low-quiescent-current negative rail generation-particularly where improved output impedance (≈100×), tighter output tolerance (±4%), and stable load regulation (<40 mV) are required.

Technical Context

The L79L08ACZ employs monolithic bipolar technology with built-in thermal shutdown and foldback current limiting, enabling robust operation without external protection circuitry. Its architecture delivers fixed -8 V output with dropout voltage of 1.7 V and supply voltage rejection of 37–45 dB at 120 Hz.

It operates over input voltage ranges scaled to its output: for -8 V output, VI is rated from -10.5 V to -23 V. Output voltage accuracy is ±4% at 25 °C and maintains ±10% over full load (1–100 mA) and line conditions, with typical output noise of 60 µV RMS (10 Hz–100 kHz).

Key Specifications

Pinout & Package

Supplied in TO-92 package (3-lead plastic transistor-style housing) with standard pinout: Pin 1 = GND, Pin 2 = Input (VIN), Pin 3 = Output (VOUT). The TO-92 variant offers low-cost through-hole mounting and moderate thermal performance (R_thj-amb = 200 °C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM7908CD, L79L08ACZ trades initial accuracy for smaller TO-92 footprint and lower thermal resistance in compact layouts; versus MC79L08CP, it guarantees ±4% tolerance and full 100 mA delivery across 0–125 °C, making it preferable for industrial temperature-range designs.

Availability

L79L08ACZ is available at Aetrix Electronics and suitable for industrial sensor conditioning, RS-232 interface power, and analog audio preamp biasing requiring stable component supply across extended temperature operation and long-term BOM continuity.

Supply support for L79L08ACZ 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-constrained and noise-sensitive analog subsystems.

FAQ

What is the minimum input voltage required for L79L08ACZ to maintain regulation?

The L79L08ACZ requires a minimum input voltage of -10.5 V to sustain -8 V output under all operating conditions, based on its 1.7 V dropout specification and datasheet test conditions. At light loads (<10 mA), regulation may hold down to -9.7 V, but -10.5 V is the guaranteed minimum per electrical characteristics table for full 100 mA output and temperature range.

Can L79L08ACZ be used in parallel to increase output current?

No-L79L08ACZ is not designed for parallel operation. Its output voltage tolerance (±4%) and lack of current-sharing features mean mismatched units would cause one device to dominate conduction, leading to thermal imbalance and potential failure. For >100 mA, use a higher-current regulator or external pass transistor configuration per the datasheet application notes.

Is an input capacitor required for stable operation?

Yes-an input capacitor of at least 0.33 µF tantalum or ceramic is recommended per the datasheet to suppress high-frequency noise and prevent oscillation due to source impedance. While the device may function without it in low-noise lab environments, omitting the input cap risks instability under real-world PCB layout conditions with trace inductance.

Does L79L08ACZ support reverse-voltage protection?

No-the L79L08ACZ has no built-in reverse-voltage protection. Applying positive voltage to VIN or reversing polarity between VIN and GND can damage the IC. External protection (e.g., series diode or MOSFET-based reverse-polarity circuit) is required in systems where incorrect connector insertion or field wiring errors are possible.