STMicroelectronics L78L15ACZ

Overview

L78L15ACZ from STMicroelectronics is a three-terminal positive linear voltage regulator delivering a fixed 15 V output at up to 100 mA, with ±4% output voltage tolerance (A-grade), thermal overload protection, short-circuit protection, and no external components required. It operates across an input voltage range of 17.5–30 V and is commonly used for local on-card regulation in industrial control modules, sensor signal conditioning circuits, and low-power microcontroller power rails.

For engineers reviewing the L78L15ACZ datasheet, L78L15ACZ pinout, L78L15ACZ application, or L78L15ACZ equivalent, this page provides verified technical context, package-specific thermal data, load/line regulation performance at 15 V, quiescent current behavior over temperature, and validated alternative options for fixed 15 V regulation in space-constrained designs.

Technical Context

The L78L15ACZ implements internal current limiting and thermal shutdown circuitry, enabling robust operation without external protection components. Its architecture integrates a bandgap reference, error amplifier, and pass transistor in a monolithic silicon structure optimized for stability with minimal external capacitance (0.33 µF input, 0.1 µF output).

It functions as a drop-in replacement for discrete Zener diode/resistor regulators, offering lower quiescent current (6.5 mA typ. at 25 °C), reduced output noise (90 µV RMS, 10 Hz–100 kHz), and improved supply voltage rejection (34–39 dB at 120 Hz) under varying line and load conditions.

Key Specifications

Pinout & Package

Supplied in TO-92 package: compact, through-hole, three-pin plastic case with standard lead spacing (2.54 mm). Pin 1 = Input, Pin 2 = Ground, Pin 3 = Output - verified per DS0424 Rev 30 Figure 2 (top view).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar fixed 15 V linear regulation applications.

Compared with LM78L15ACZ and MC78L15ACPRAG, the L78L15ACZ delivers tighter output tolerance (±4% vs. ±5%), superior supply rejection (34–39 dB vs. ≤35 dB), and lower thermal resistance (200 °C/W vs. 220 °C/W), making it optimal for noise-sensitive, thermally constrained, or accuracy-critical 15 V local regulation.

Availability

L78L15ACZ is available at Aetrix Electronics and suitable for industrial sensor nodes, PLC I/O modules, embedded controller auxiliary rails, and legacy equipment voltage retrofits requiring stable component supply with full traceability and long-lifecycle support.

Supply support for L78L15ACZ 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 L78L series belongs to ST's legacy linear regulator product line, engineered specifically for cost-sensitive, space-constrained applications requiring reliable fixed-voltage regulation without external components.

FAQ

What is the minimum input voltage required for regulation at 15 V output?

The L78L15ACZ requires a minimum input voltage of 17.5 V to maintain regulation at full 100 mA load, based on its 1.7 V dropout specification (VI ≥ VO + Vd). At lighter loads (<10 mA), regulation holds down to ~16.7 V, but design margin should retain 17.5 V minimum per DS0424 Table 19.

Can L78L15ACZ be used in surface-mount designs?

No-the L78L15ACZ is only offered in through-hole TO-92 packaging per ST's official datasheet (DS0424 Rev 30, Section 7.1). ST does not manufacture an SMT variant of this specific part number; SO-8 and SOT-89 variants exist for other L78Lxx members but not for L78L15ACZ.

How does thermal performance differ between TO-92 and SO-8 packages for L78L regulators?

Per DS0424 Table 2, the TO-92 package has R_thJA = 200 °C/W (unmounted), while SO-8 achieves 55 °C/W with 6 cm² copper heatsink. For L78L15ACZ at 100 mA and 25 °C ambient, TO-92 junction temperature rises ~20 °C above ambient, whereas SO-8 would rise only ~5.5 °C-enabling higher sustained current or elevated ambient operation.

Is L78L15ACZ compatible with ceramic output capacitors?

Yes-ST explicitly qualifies the L78L15ACZ for stable operation with 0.1 µF ceramic output capacitors (X7R or better), as confirmed in DS0424 Section 4 test conditions and Figure 9 output characteristics. No ESR requirements apply, unlike older 78xx regulators.