STMicroelectronics L78M05CDT

Overview

L78M05CDT from STMicroelectronics is a three-terminal positive fixed-voltage linear regulator delivering 5 V ±4 % at up to 0.5 A output current in TO-220FP package. It integrates thermal overload protection, short-circuit current limiting, and safe operating area (SOA) protection, and operates across 0 to 150 °C junction temperature range. It serves as a local on-card DC power supply for microcontroller peripherals, sensor interfaces, and industrial control logic.

For engineers reviewing the L78M05CDT datasheet, L78M05CDT pinout, L78M05CDT application, or L78M05CDT equivalent, key selection criteria include guaranteed 5 V output tolerance (±4 %), 2 V dropout voltage at 25 °C, 62 dB supply voltage rejection at 120 Hz, 40 µV output noise (10 Hz–100 kHz), and compatibility with standard TO-220FP heatsinking layouts.

Technical Context

The L78M05CDT implements a monolithic NPN pass transistor architecture with internal bandgap reference, error amplifier, and protection circuitry. Its SOA compensation dynamically reduces short-circuit current as input-output differential voltage increases, preventing thermal runaway during fault conditions.

It requires no external compensation for stability but benefits from a 0.33 µF input bypass capacitor when placed >5 cm from bulk filter capacitance. Output capacitance (≥0.1 µF) improves transient response but is not mandatory for regulation stability.

Key Specifications

Pinout & Package

Package: TO-220FP (Full Pack), 3-pin vertical mounting variant with insulated tab; R_thJC = 5 °C/W, R_thJA = 60 °C/W; compatible with standard TO-220 heatsinks using insulating washers.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM78M05CDT and MC78M05CDTG, the L78M05CDT offers superior supply ripple rejection and lower dropout-critical for space-constrained industrial boards with marginal input headroom and noisy upstream converters.

Availability

L78M05CDT is available at Aetrix Electronics and suitable for industrial PLC I/O modules, automotive body control units, medical patient monitor front-ends, and point-of-sale terminal power management requiring stable component supply and long-term lifecycle support.

Supply support for L78M05CDT 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 L78M series belongs to ST's precision 500 mA linear regulator product line, engineered for cost-sensitive, high-reliability applications demanding integrated protection and extended temperature operation without external components.

FAQ

What is the minimum input voltage required for stable 5 V output at 500 mA?

The L78M05CDT requires a minimum input voltage of 7 V to maintain regulation at full 500 mA load, based on its 2 V dropout voltage specification at 25 °C. At elevated junction temperatures (>100 °C), dropout increases slightly; design margin recommends ≥7.5 V input for robust operation across the full 0–150 °C junction range.

Can L78M05CDT be used without input or output capacitors?

Yes-the L78M05CDT is internally compensated and does not require output capacitance for stability. However, an input bypass capacitor (≥0.33 µF) is strongly recommended when the regulator is located >5 cm from bulk filter capacitance to prevent oscillation under fast load transients. Output capacitance (≥0.1 µF) improves transient response but is optional.

How does thermal shutdown behave during sustained overload?

When junction temperature reaches ~150 °C, the L78M05CDT disables the pass transistor and holds output at 0 V until temperature falls by ~15 °C. This hysteresis prevents rapid cycling. During shutdown, quiescent current drops to ~1 mA, minimizing heat generation while waiting for thermal recovery-enabling automatic, safe self-reset without external intervention.

Is L78M05CDT pin-compatible with older 78M05 variants from other manufacturers?

Yes-L78M05CDT uses standard TO-220FP pinout (Input–Ground–Output) identical to LM78M05CDT and MC78M05CDTG. Mechanical dimensions and thermal pad layout match industry-standard TO-220FP footprints, allowing direct replacement in existing PCBs without layout modification, provided thermal design margins accommodate the 5 °C/W junction-to-case resistance.