STMicroelectronics L78L05CZ

Overview

L78L05CZ from STMicroelectronics is a three-terminal positive linear voltage regulator delivering a fixed 5 V output at up to 100 mA, with ±8% output tolerance, thermal overload protection, short-circuit protection, and no external components required. It operates across an input range of 7–20 V and is used for local on-card regulation in microcontroller power rails, sensor interfaces, and low-power industrial control modules.

For engineers reviewing the L78L05CZ datasheet, L78L05CZ pinout, L78L05CZ application, or L78L05CZ equivalent, this page provides verified electrical characteristics, TO-92 package details, thermal performance data, load/line regulation behavior, and validated alternative parts for cost, temperature, or packaging trade-offs.

Technical Context

The L78L05CZ integrates internal current limiting and thermal shutdown circuitry, enabling robust operation without external protection components. Its architecture uses a bandgap reference and error amplifier to maintain stable 5 V output under varying load (1–100 mA) and line (7–20 V) conditions.

It exhibits 30 mV load regulation (1–40 mA), 100 mV line regulation (8–20 V), 40 µV RMS output noise (10 Hz–100 kHz), and 41–49 dB supply voltage rejection at 120 Hz - confirming suitability for noise-sensitive analog and mixed-signal subsystems.

Key Specifications

Pinout & Package

Supplied in TO-92 package: compact, through-hole, thermally optimized plastic case with 3 leads. Pin 1 = Input, Pin 2 = Ground, Pin 3 = Output. Standard lead spacing (2.54 mm) and footprint compatible with manual soldering and wave processes.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC78L05ACPRAG, L78L05CZ offers superior supply ripple rejection and higher guaranteed output voltage accuracy at room temperature, while L78L05ACZ trades minor cost increase for broader temperature coverage and tighter tolerance - making it preferable for mission-critical embedded control.

Availability

L78L05CZ is available at Aetrix Electronics and suitable for industrial sensor nodes, legacy MCU power rails, low-power IoT edge devices, and programmable logic interfaces requiring stable component supply across long-lifecycle production programs.

Supply support for L78L05CZ 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, power, microcontroller, and sensor solutions for industrial, automotive, and consumer markets.

The L78L series belongs to ST's legacy linear regulator product line, engineered for cost-sensitive, high-reliability local regulation in space-constrained and thermally demanding environments - emphasizing ruggedness, simplicity, and long-term availability.

FAQ

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

The L78L05CZ requires a minimum input voltage of 7 V to maintain regulation at full 100 mA load, based on its 2 V dropout voltage specification. At lighter loads (e.g., 10 mA), input can be reduced to ~6.5 V, but design margin should retain ≥7 V to ensure stability across temperature and tolerance variations.

Can L78L05CZ be used in parallel to increase output current?

No - the L78L05CZ lacks built-in current-sharing features and has no matching output voltage tolerance tight enough to prevent current hogging. Parallel connection risks thermal runaway and premature failure. For >100 mA, use a single higher-current regulator (e.g., L7805CD2T) or add an external pass transistor per Figure 14 in DS0424.

Is a heat sink required for continuous 100 mA operation in TO-92?

In still air with standard 1 oz copper on a 2-layer PCB, the TO-92 package reaches ~115 °C junction temperature at 100 mA with 12 V input - within safe limits but near thermal shutdown threshold. A small copper pour (≥2 cm²) on the ground pad significantly improves thermal resistance and is recommended for sustained full-load operation.

Does L78L05CZ support reverse-input protection?

No - the device lacks internal reverse-polarity protection. Applying negative voltage to Pin 1 relative to Pin 2 may cause latch-up or permanent damage. An external series diode (e.g., 1N4001) is required if input polarity reversal is possible in the application environment.