STMicroelectronics L78L33ABUTR

Overview

L78L33ABUTR 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 overload protection, and short-circuit protection. It requires no external components, operates across -40 °C to +125 °C junction temperature, and maintains ±4% output voltage tolerance (A-grade) for use in low-noise local regulation on embedded control boards.

For engineers reviewing the L78L33ABUTR datasheet, L78L33ABUTR pinout, L78L33ABUTR application, or L78L33ABUTR equivalent, this device serves as a drop-in replacement for Zener-diode/resistor regulators in space-constrained industrial and automotive subsystems where quiescent current below 6 mA and output noise under 40 µV are critical.

Technical Context

The L78L33ABUTR employs monolithic silicon construction with built-in thermal shutdown and foldback current limiting, enabling robust operation without external protection circuitry. Its architecture delivers stable regulation even with input voltages as low as 5.3 V and up to 20 V (for 3.3 V output), maintaining load regulation within ±30 mV over 1–40 mA output current.

It achieves 41–49 dB supply voltage rejection at 120 Hz with 40 µV RMS output noise (10 Hz–100 kHz bandwidth), and exhibits a dropout voltage of 2 V - meaning it sustains regulation when input exceeds output by ≥2 V. The device supports TO-92, SO-8, and SOT-89 packages, with thermal resistance junction-to-ambient of 200 °C/W (TO-92) and 55 °C/W (SO-8 with 6 cm² copper heatsink).

Key Specifications

Pinout & Package

Supplied in TO-92 package (3-pin, through-hole), with standard pin configuration: Pin 1 = Input, Pin 2 = Ground, Pin 3 = Output. The package features a compact 4.95 mm × 3.94 mm × 15.49 mm outline and is RoHS-compliant per ECOPACK2 specification.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM78L33ACZ and MCP1700T-3302E/TT, the L78L33ABUTR uniquely balances industrial-grade temperature range, ±4% accuracy, full fault protection, and proven reliability in safety-critical embedded systems - making it the preferred choice for long-lifecycle OEM deployments.

Availability

L78L33ABUTR is available at Aetrix Electronics and suitable for industrial sensor nodes, automotive body electronics, medical wearables, and POS peripheral interfaces requiring stable component supply across multi-year production cycles.

Supply support for L78L33ABUTR 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 silicon solutions for automotive, industrial, and consumer markets since 1987.

The L78L series belongs to ST's legacy linear regulator product line, engineered specifically for cost-effective, robust local regulation in space- and reliability-constrained embedded systems - emphasizing simplicity, fault resilience, and wide-temperature operation.

FAQ

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

The L78L33ABUTR requires a minimum input voltage of 5.3 V to maintain regulation at full load (100 mA) and room temperature. At light loads (1–40 mA), it sustains regulation down to 5.3 V due to its 2 V dropout voltage - meaning input must exceed output by ≥2 V. Below 5.3 V, output collapses nonlinearly.

Can L78L33ABUTR be used in parallel to increase output current?

No - the L78L33ABUTR is not designed for parallel operation. Its output voltage tolerance (±4%) and thermal characteristics cause unequal current sharing, risking thermal runaway in one device. For >100 mA, use a higher-current regulator (e.g., L78M33) or add an external pass transistor per Figure 14 in DS0424.

Does this part support reverse-polarity input protection?

No - the L78L33ABUTR has no internal reverse-voltage protection. Applying negative voltage to the input pin (Pin 1) relative to ground (Pin 2) may cause latch-up or permanent damage. An external series diode or dedicated protection IC is required in systems prone to wiring reversal or battery insertion errors.

Is the TO-92 package RoHS-compliant and lead-free?

Yes - the L78L33ABUTR in TO-92 packaging meets RoHS Directive 2011/65/EU and is manufactured with lead-free terminations per STMicroelectronics' ECOPACK2 specification. The device carries the "RoHS-compliant" marking on the package body and is qualified for reflow soldering per JEDEC J-STD-020.