STMicroelectronics L78L12ACZ

Overview

L78L12ACZ from STMicroelectronics is a three-terminal positive linear voltage regulator delivering a fixed 12 V output at up to 100 mA, featuring internal current limiting, thermal overload protection, and short-circuit protection. It requires no external components for basic operation and is rated for 0 to 125 °C junction temperature, with ±4% output voltage tolerance (A-grade). It serves as a local on-card regulator in industrial control modules, sensor signal conditioning circuits, and low-power microcontroller power rails.

For engineers reviewing the L78L12ACZ datasheet, L78L12ACZ pinout, L78L12ACZ application, or L78L12ACZ equivalent, this device is evaluated for fixed-voltage local regulation where dropout voltage (1.7 V), quiescent current (6.5 mA at 25 °C), output noise (80 µV RMS), supply voltage rejection (37–42 dB), and thermal shutdown behavior are critical selection criteria.

Technical Context

The L78L12ACZ employs monolithic bipolar silicon technology with built-in foldback current limiting and thermal shutdown circuitry, ensuring robustness under sustained overload or elevated ambient conditions. Its architecture eliminates need for external compensation or feedback networks, operating as a self-contained regulator with only input and output capacitors required for stability.

It functions as a series pass regulator with a PNP transistor-based pass element, referenced to an internal bandgap voltage source. The device maintains regulation across input voltages from 14.5 V to 27 V (min/max specified), supporting applications where input ripple rejection (≥37 dB at 120 Hz) and load regulation (≤50 mV over 1–40 mA) are essential for analog subsystem integrity.

Key Specifications

Pinout & Package

Supplied in TO-92 package (3-pin, through-hole), with standardized pinout: Pin 1 = Input, Pin 2 = Ground, Pin 3 = Output. The package uses epoxy-molded plastic construction with lead-free (RoHS-compliant) terminations and ECOPACK2 environmental grade.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM78L12ACZ and MC78L12ACP, the L78L12ACZ delivers superior output accuracy (±4% vs. ±5%), higher PSRR (37–42 dB vs. ≤40 dB), guaranteed operation to 125 °C, and optimized thermal resistance-making it the preferred choice for industrial and precision analog applications demanding long-term stability and robustness.

Availability

L78L12ACZ is available at Aetrix Electronics and suitable for industrial sensor nodes, microcontroller I/O power, legacy equipment upgrades, and low-power analog front-ends requiring stable component supply with consistent parametric performance across production batches.

Supply support for L78L12ACZ 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 automotive, industrial, and consumer markets.

The L78L series belongs to ST's legacy linear regulator product line, engineered specifically for cost-sensitive, space-constrained applications requiring rugged, no-frills fixed-voltage regulation with integrated protection-targeting industrial controls, instrumentation, and embedded subsystems.

FAQ

What is the minimum input voltage required for L78L12ACZ to maintain regulation?

The L78L12ACZ requires a minimum input voltage of 14.5 V to sustain 12 V output under full 40 mA load at 25 °C, based on its 1.7 V typical dropout voltage. At higher temperatures or loads approaching 100 mA, input should be ≥15.5 V to ensure margin against dropout and thermal derating.

Can L78L12ACZ be used in parallel to increase output current?

No-L78L12ACZ is not designed for parallel operation. Its output voltage tolerance (±4%) and lack of current-sharing features mean mismatched units will cause one device to dominate conduction, leading to thermal imbalance and potential failure. For >100 mA, use a single higher-current regulator or external pass transistor configuration per Figure 13 in DS0424.

Is L78L12ACZ RoHS-compliant and halogen-free?

Yes-L78L12ACZ is manufactured in STMicroelectronics' ECOPACK2-compliant TO-92 package, meeting RoHS Directive 2011/65/EU and containing ≤900 ppm bromine and ≤900 ppm chlorine per homogeneous material, verified per IEC 62321 testing standards.

How does thermal performance differ between TO-92 and SO-8 packages for L78L12AC?

The TO-92 package has R_thJA = 200 °C/W (no heatsink), limiting continuous 100 mA operation to ≤50 °C ambient unless PCB copper area is added. The SO-8 variant (L78L12ACD) achieves R_thJA = 55 °C/W with 6 cm² copper, enabling full 100 mA output up to 100 °C ambient-making SO-8 preferable for high-density or thermally constrained designs.