STMicroelectronics L78M05CDT-TR

Overview

L78M05CDT-TR 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 (IPAK) 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 power supply for microcontroller I/O rails, sensor biasing, and industrial control logic.

For engineers reviewing the L78M05CDT-TR datasheet, L78M05CDT-TR pinout, L78M05CDT-TR application, or L78M05CDT-TR equivalent, key selection criteria include guaranteed 5 V output tolerance (±4 %), 2 V dropout voltage at 350 mA, 62 dB supply voltage rejection at 120 Hz, 40 µV RMS output noise (10 Hz–100 kHz), and thermal shutdown activation at T_J ≥ 150 °C.

Technical Context

The L78M05CDT-TR implements a monolithic PNP pass transistor with internal bandgap reference, error amplifier, and protection circuitry. Its SOA compensation dynamically reduces short-circuit current as V_CE increases, preventing second breakdown during fault conditions.

It requires no external compensation for stability but benefits from a 0.33 µF input ceramic/tantalum capacitor when placed >5 cm from bulk filter, and a 0.1 µF output capacitor improves transient response. Input voltage range is 7–25 V for reliable 5 V regulation at full load.

Key Specifications

Pinout & Package

TO-220FP (IPAK) package: 3-pin vertical mount with isolated tab (pin 2 = GND), standard footprint compatible with TO-220 heatsinks. Tab is electrically connected to Pin 2 (GND).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM78M05CDT-TR, the L78M05CDT-TR delivers superior supply ripple rejection and lower quiescent current-critical for battery-powered or noise-sensitive systems-while the MC78M05CDTG offers surface-mount compatibility at the expense of thermal resistance.

Availability

L78M05CDT-TR is available at Aetrix Electronics and suitable for industrial automation, automotive body electronics, medical instrumentation, and smart metering requiring stable component supply and long-term lifecycle support.

Supply support for L78M05CDT-TR 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 power management applications.

The L78M series belongs to ST's precision 500 mA linear regulator product line, engineered for ruggedness in harsh environments-featuring integrated SOA protection, extended temperature operation, and high reliability for mission-critical power domains.

FAQ

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

The L78M05CDT-TR requires a minimum input voltage of 7 V to maintain regulation at full 500 mA load, based on its 2 V dropout specification. At 350 mA, VI ≥ 7 V is sufficient; at 500 mA, VI must be ≥ 7 V with margin for line regulation (±100 mV) and thermal derating. Below 7 V, output voltage collapses nonlinearly.

Can this regulator be used without input or output capacitors?

A 0.33 µF input capacitor is mandatory if the regulator is located >5 cm from the bulk filter or powered via long wires, per ST's design guidelines. An output capacitor is not required for stability but strongly recommended: a 0.1 µF ceramic capacitor significantly improves load transient response and reduces output impedance above 10 kHz.

How does thermal shutdown behave during continuous overload?

Thermal shutdown activates at T_J ≥ 150 °C and forces output to zero. The device remains latched off until junction temperature falls below ~135 °C (hysteresis ≈15 °C), then resumes regulation automatically. This cycle repeats under sustained overload, protecting both the IC and PCB-no external reset or latch circuit is needed.

Is the tab electrically isolated in the TO-220FP package?

No-the metal tab in the TO-220FP (IPAK) package is internally connected to Pin 2 (GND). When mounted to a heatsink, the heatsink must be insulated from other potentials unless intentionally grounded. ST specifies isolation voltage ≤ 50 V between tab and other pins; use insulating pads or shoulder washers if mounting to chassis ground.