STMicroelectronics L78L05ABZ

Overview

L78L05ABZ from STMicroelectronics is a three-terminal positive 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 operates across an input voltage range of 7–20 V with ±4% output tolerance (AB grade), 40 µV output noise, and 41–49 dB supply voltage rejection at 120 Hz - deployed in local on-card regulation for microcontroller power domains, sensor interfaces, and low-power industrial control modules.

For engineers reviewing the L78L05ABZ datasheet, L78L05ABZ pinout, L78L05ABZ application, or L78L05ABZ equivalent, this device serves as a robust, no-external-components solution for noise-sensitive 5 V rail generation where thermal resilience, quiescent current stability (6 mA typ. at 25 °C), and dropout voltage of 2 V are critical selection criteria.

Technical Context

The L78L05ABZ implements a monolithic silicon-based series pass regulator architecture with built-in foldback current limiting and thermal overload protection. Its AB-grade specification guarantees operation over –40 °C to +125 °C junction temperature, enabling use in extended-temperature industrial environments without derating.

It requires only two external capacitors (CI = 0.33 µF, CO = 0.1 µF) for stability and ripple suppression, and achieves load regulation of ≤30 mV (1–40 mA) and line regulation of ≤100 mV (8–20 V input), making it suitable for point-of-load regulation where input transients and load steps must be tightly controlled.

Key Specifications

Pinout & Package

Supplied in TO-92 package (3-pin, vertical mounting), with lead material compliant to RoHS and ECOPACK2 standards. Thermal resistance junction-to-ambient is 200 °C/W (no PCB copper heatsink), reduced significantly with board copper area.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar fixed-output linear regulator applications.

Compared with LM78L05ACZ and MC78L05ACP, the L78L05ABZ provides tighter output accuracy, lower noise, superior SVR, and guaranteed operation down to –40 °C - making it the preferred choice for industrial and automotive-adjacent embedded systems requiring long-term stability and thermal resilience.

Availability

L78L05ABZ is available at Aetrix Electronics and suitable for industrial sensor nodes, embedded MCU power rails, and low-power IoT edge devices requiring stable component supply with full traceability and lifecycle continuity.

Supply support for L78L05ABZ 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, MCU, power, and sensing solutions for industrial, automotive, and consumer markets.

The L78L series belongs to ST's legacy linear regulator product line, engineered specifically for cost-effective, robust local regulation in resource-constrained embedded systems where simplicity, reliability, and wide temperature operation are prioritized over ultra-low IQ or adjustable output.

FAQ

What is the minimum input voltage required for L78L05ABZ to maintain regulation?

The L78L05ABZ requires a minimum input voltage of 7 V to sustain 5 V output under full 100 mA load, based on its 2 V dropout voltage specification. At lighter loads (e.g., 40 mA), regulation holds down to ~6.5 V input, but design margin should preserve ≥7 V to ensure stability across temperature and line variations.

Can L78L05ABZ be used in parallel to increase output current?

No - the L78L05ABZ is not designed for parallel operation. Its output voltage tolerance (±4%) and lack of current-sharing circuitry cause unequal load distribution, risking thermal runaway in one unit. For >100 mA, use a single higher-current regulator (e.g., L7805) or add an external pass transistor per Figure 14 in DS0424.

Is a heat sink required for continuous 100 mA operation?

At 100 mA with 12 V input, power dissipation is ~0.7 W. In TO-92 with no PCB copper heatsink (R_thJA = 200 °C/W), junction temperature rise would exceed safe limits. A minimum 2 cm² copper pour is recommended; for enclosed or high-ambient environments, a small clip-on heatsink or SO-8 variant (L78L05ABD) improves thermal margin.

Does L78L05ABZ require input/output capacitors, and what values are validated?

Yes - ST specifies 0.33 µF ceramic at the input and 0.1 µF ceramic at the output, placed as close as possible to the respective pins. These values ensure stability across all operating conditions and suppress high-frequency noise; substituting with larger electrolytics or omitting either capacitor risks oscillation or degraded transient response.