STMicroelectronics L78L05ACZTR

Overview

L78L05ACZTR 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 requires no external components, operates with input voltages up to 30 V (for 5 V output), and maintains ±4% output tolerance over 0–125 °C junction temperature. It is used for local on-card regulation in microcontroller power rails, sensor interfaces, and low-power industrial control modules.

For engineers reviewing the L78L05ACZTR datasheet, L78L05ACZTR pinout, L78L05ACZTR application, or L78L05ACZTR equivalent, this device serves as a robust, drop-in replacement for legacy 78L05 regulators in space-constrained PCBs where thermal reliability and noise-sensitive analog supply integrity are critical.

Technical Context

The L78L05ACZTR employs monolithic bipolar silicon technology with built-in foldback current limiting and thermal overload protection, enabling self-recovery after fault conditions. Its architecture eliminates need for external compensation or bypass capacitors beyond minimum recommended input/output ceramic decoupling (0.33 µF / 0.1 µF).

It operates across an input-to-output differential range of 2 V (dropout) to 25 V, with line regulation of ≤100 mV and load regulation of ≤30 mV under nominal conditions. Output noise is specified at 40 µV RMS (10 Hz–100 kHz), and supply voltage rejection reaches 49 dB at 120 Hz.

Key Specifications

Pinout & Package

Supplied in TO-92 package (3-pin plastic transistor outline), with standardized pinout: Pin 1 = Input, Pin 2 = Ground, Pin 3 = Output. The package supports through-hole mounting and provides R_thJA = 200 °C/W (no heatsink) or ≤100 °C/W with 6 cm² copper pour.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM78L05ACZ/NOPB and MC78L05ACP, the L78L05ACZTR offers tighter output tolerance, lower noise, superior PSRR, and formal environmental compliance-making it optimal for new designs demanding long-term supply stability and performance consistency.

Availability

L78L05ACZTR is available at Aetrix Electronics and suitable for industrial control I/O modules, sensor interface boards, and embedded microcontroller power supplies requiring stable component supply, long lifecycle support, and RoHS-compliant sourcing.

Supply support for L78L05ACZTR 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 ruggedness, simplicity, and guaranteed thermal safety without external protection circuitry.

FAQ

What is the minimum input voltage required for stable 5 V output at 100 mA?

The L78L05ACZTR has a typical dropout voltage of 2.0 V. To deliver 5.0 V at 100 mA, the input voltage must be ≥7.0 V. At lower inputs (e.g., 6.5 V), output regulation degrades rapidly and may fall below 4.75 V - verified per Table 4 in DS0424 Rev 30.

Can this regulator be used with ceramic output capacitors only?

Yes. The L78L05ACZTR is stable with a minimum 0.1 µF ceramic capacitor on the output (and 0.33 µF on input), as confirmed in all test circuits (Figures 3, 13–16). Unlike older 78xx variants, it does not require ESR-based damping and avoids instability with low-ESR ceramics.

Does the TO-92 package require a heatsink for 100 mA operation?

No external heatsink is required for 100 mA at ambient ≤50 °C with standard PCB layout. Thermal resistance is 200 °C/W (junction-to-ambient, no copper pour); with 6 cm² copper area, R_thJA drops to ~100 °C/W, keeping junction temperature safely below 125 °C even at 70 °C ambient.

How does the L78L05ACZTR differ from the L78L05AB variant?

The 'C' suffix denotes 0–125 °C operating junction range and ±4% output tolerance; the 'B' suffix extends temperature range to -40–125 °C but retains ±4% tolerance. Both share identical electrical specs, pinout, and package - selection depends solely on minimum ambient operating temperature requirement.