STMicroelectronics L78L33ABZ-AP

Overview

L78L33ABZ-AP from STMicroelectronics is a three-terminal positive linear voltage regulator delivering a fixed 3.3 V output at up to 100 mA, featuring internal current limiting, thermal shutdown, and short-circuit protection. It requires no external components, operates across -40°C to +125°C junction temperature, and provides ±4% output voltage tolerance (A-grade) in TO-92 package-ideal for local regulation on microcontroller power rails in industrial control modules.

For engineers reviewing the L78L33ABZ-AP datasheet, L78L33ABZ-AP pinout, L78L33ABZ-AP application, or L78L33ABZ-AP equivalent, key selection criteria include dropout voltage (2 V), quiescent current (6 mA at 25°C), supply voltage rejection (41–49 dB at 120 Hz), and thermal performance in constrained PCB layouts without heatsinking.

Technical Context

The L78L33ABZ-AP implements a monolithic silicon-based series pass regulator with built-in foldback current limiting and thermal overload protection. Its architecture ensures safe operation under sustained overload or ambient temperature extremes without external intervention.

It maintains stable 3.3 V output across input voltages from 5.3 V to 20 V and load currents from 1 mA to 100 mA, with line regulation ≤100 mV and load regulation ≤30 mV under specified conditions-enabling reliable low-noise biasing for analog sensors and digital logic interfaces.

Key Specifications

Pinout & Package

Supplied in TO-92 plastic 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).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM3940IT-3.3/NOPB and MCP1700T-3302E/TT, the L78L33ABZ-AP offers superior fault resilience (thermal/short-circuit protection), TO-92 mechanical compatibility, and proven performance in high-temperature industrial settings-making it optimal where reliability outweighs ultra-low IQ or minimal dropout.

Availability

L78L33ABZ-AP is available at Aetrix Electronics and suitable for industrial PLC I/O modules, automotive body control units, medical sensor nodes, and smart energy meter subsystems requiring stable component supply across extended temperature ranges and multi-year production cycles.

Supply support for L78L33ABZ-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 L78L series belongs to ST's legacy linear regulator product line, engineered specifically for cost-sensitive, high-reliability local regulation in space-constrained embedded systems where simplicity, ruggedness, and wide temperature operation are prioritized over ultra-low quiescent current.

FAQ

What is the minimum input voltage required for stable 3.3 V output?

The L78L33ABZ-AP requires a minimum input voltage of 5.3 V to maintain regulated 3.3 V output at full 100 mA load, based on its 2 V dropout specification. At lighter loads (<10 mA), input can drop to ~4.5 V while retaining regulation, but design margin should retain ≥5.3 V to ensure performance across temperature and process variation.

Can this regulator be used with ceramic output capacitors?

Yes-the L78L33ABZ-AP is stable with ceramic output capacitors ≥0.1 µF, as confirmed in ST's DS0424 Rev 30 test conditions. Unlike older 78xx variants, it does not require ESR-based damping; standard X7R/X5R ceramics meet stability requirements without series resistance.

Does the TO-92 package support 100 mA continuous output?

Yes, but only with adequate PCB copper area acting as heatsink. In free-air (no copper pour), thermal resistance is 200°C/W; at 100 mA with 5 V dropout (0.5 W dissipation), junction temperature rises ~100°C above ambient-so operation at 100 mA is viable up to ~25°C ambient. For higher ambient, reduce load or add ≥6 cm² copper pad.

How does the ±4% output tolerance affect ADC reference accuracy?

With ±4% tolerance (±0.132 V), the L78L33ABZ-AP delivers 3.168–3.432 V output at 25°C. When used as an ADC reference, this introduces up to ±2% full-scale error in 10-bit conversions. For higher accuracy, pair with external trimming or use a dedicated voltage reference IC instead.